@Article{ 2015,
title = {Transcranial magnetic stimulation in the visual system: I. The psychophysics of visual suppression},
journal = {Experimental Brain Research},
year = {2005},
month = {1},
volume = {160},
number = {1},
pages = {118-128},
abstract = {When applied over the occipital pole, transcranial magnetic stimulation (TMS) disrupts visual perception and induces phosphenes. Both the underlying mechanisms and the brain structures involved are still unclear. The first part of the study characterizes the suppressive effect of TMS by psychophysical methods. Luminance increment thresholds for orientation discrimination were determined in four subjects using an adaptive staircase procedure. Coil position was controlled with a stereotactic positioning device. Threshold values were modulated by TMS, reaching a maximum effect at a stimulus onset asynchrony (SOA) of approx. 100 ms after visual target presentation. Stronger TMS pulses increased the maximum threshold while decreasing the SOA producing the maximum effect. Slopes of the psychometric function were flattened with TMS masking by a factor of 2, compared to control experiments in the absence of TMS. No change in steepness was observed in experiments using a light flash as the mask instead of TMS. Together with the finding that at higher TMS intensities, threshold elevation occurs even with shorter SOAs, this suggests lasting inhibitory processes as masking mechanisms, contradicting the assumption that the phosphene as excitatory equivalent causes masking. In the companion contribution to this one we present perimetric measurements and phosphene forms as a function of the stimulation site in the brain and discuss the putative generator structures.},
file_url = {/fileadmin/user_upload/files/publications/pdf2015.pdf},
web_url = {http://www.springerlink.com/content/ehng02udm3jcecha/fulltext.pdf},
state = {published},
DOI = {10.1007/s00221-004-1991-1},
author = {Kammer T{kammer}{Department Human Perception, Cognition and Action}, Puls K{puls}{Department Human Perception, Cognition and Action}, Strasburger H, Hill NJ{jez} and Wichmann FA{felix}}
}

@Article{ 2016,
title = {Transcranial magnetic stimulation in the visual system: II. Characterization of induced phosphenes and scotomas},
journal = {Experimental Brain Research},
year = {2005},
month = {1},
volume = {160},
number = {1},
pages = {129-140},
abstract = {Transcranial magnetic stimulation (TMS) induces phosphenes and disrupts visual perception when applied over the occipital pole. Both the underlying mechanisms and the brain structures involved are still unclear. In the first part of this study we show that the masking effect of TMS differs to masking by light in terms of the psychometric function. Here we investigate the emergence of phosphenes in relation to perimetric measurements. The coil positions were measured with a stereotactic positioning device, and stimulation sites were characterized in four subjects on the basis of individual retinotopic maps measured by with functional magnetic resonance imaging. Phosphene thresholds were found to lie a factor of 0.59 below the stimulation intensities required to induce visual masking. They covered the segments in the visual field where visual suppression occurred with higher stimulation intensity. Both phosphenes and transient scotomas were found in the lower visual field in the quadrant contralateral to the st
imulated hemisphere. They could be evoked from a large area over the occipital pole. Phosphene contours and texture remained quite stable with different coil positions over one hemisphere and did not change with the retinotopy of the different visual areas on which the coil was focused. They cannot be related exclusively to a certain functionally defined visual area. It is most likely that both the optic radiation close to its termination in the dorsal parts of V1 and back-projecting fibers from V2 and V3 back to V1 generate phosphenes and scotomas.},
file_url = {/fileadmin/user_upload/files/publications/pdf2016.pdf},
web_url = {http://www.springerlink.com/content/1xl5g0egbnrr41g9/fulltext.pdf},
state = {published},
DOI = {10.1007/s00221-004-1992-0},
author = {Kammer T{kammer}{Department Human Perception, Cognition and Action}, Puls K{puls}{Department Human Perception, Cognition and Action}, Erb M and Grodd W}
}

@Article{ 2017,
title = {Combining backward masking and transcranial magnetic stimulation in human observers},
journal = {Neuroscience Letters},
year = {2003},
month = {6},
volume = {343},
number = {3},
pages = {171-174},
abstract = {Both backward masking and transcranial magnetic stimulation (TMS) are capable of hindering perception of a visual target. To study the relationship between these two methods we applied TMS over the occipital pole in combination with the recently discovered weak visual backward masking technique shine-through. In three subjects we determined discrimination thresholds for vernier acuity by means of a 2AFC task. The time course of target processing was investigated by varying the stimulus onset asynchrony (SOA) of TMS for an unmasked vernier target. Vernier offset discrimination deteriorates moderately around 120 ms TMS SOA. If in addition to TMS the vernier is backward-masked, discrimination of the vernier offset is completely abolished. Therefore, TMS and backward masking can interact in a non-linear manner, strongly interfering with early visual processing.},
web_url = {http://www.sciencedirect.com/science/article/pii/S0304394003003768},
state = {published},
DOI = {10.1016/S0304-3940(03)00376-8},
author = {Kammer T{kammer}, Scharnowski F{franks} and Herzog MH}
}

@Article{ 1591,
title = {Propofol and Sevoflurane in Subanesthetic Concentrations Act Preferentially on the Spinal Cord: Evidence from Multimodal Electrophysiological Assessment},
journal = {Anesthesiology},
year = {2002},
month = {12},
volume = {97},
number = {6},
pages = {1416-1425},
abstract = {Background:
Animal experiments in recent years have shown that attenuation of motor responses by general anesthetics is mediated at least partly by spinal mechanisms. Less is known about the relative potency of anesthetic drugs in suppressing cortical and spinal electrophysiological responses in vivo in humans, particularly those but not only those connected with motor responses. Therefore, we studied the effects of sevoflurane and propofol in humans using multimodal electrophysiological assessment.
Methods:
We studied 9 healthy volunteers in two sessions during steady-state sedation with either 0.5, 1.0, and 1.5 µg/l (targeted plasma concentration) propofol or 0.2 and 0.4 vol% (end-tidal) sevoflurane. Following a 15 min equilibration period, motor responses to transcranial magnetic stimulation (TMS) and peripheral (H-reflex, F-wave) stimulation were recorded, while electroencephalography and auditory evoked responses were recorded in parallel.
Results:
At concentrations corresponding to 2/3 of C50awake motor responses to TMS were reduced by about 50%, H-reflex amplitude by 22%, F-wave amplitude by 40%, and F-wave persistence by 25%. No significant differences between sevoflurane and propofol were found. At this concentration the bispectral index was reduced by 7% and the middle-latency auditory evoked responses were attenuated only mildly (Nb latency increased by 11%, amplitude PaNb did not change). In contrast, the postauricular reflex was suppressed by 77%.
Conclusions:
The large effect of both anesthetics on all spinal motor responses, compared to the small effect on electroencephalography and middle-latency auditory evoked responses – assuming that they represent cortical modulation, may suggest that the suppression of motor responses to TMS is largely due to submesencephalic effects.},
file_url = {/fileadmin/user_upload/files/publications/pdf1591.pdf},
web_url = {http://journals.lww.com/anesthesiology/pages/articleviewer.aspx?year=2002&issue=12000&article=00013&type=abstract},
state = {published},
author = {Kammer T{kammer}, Rehberg B, Menne D, Wartenberg HC, Wenningmann I and Urban BW}
}

@Article{ 1592,
title = {Linking physics with physiology in TMS: 
A sphere field model to determine
the cortical stimulation site in TMS},
journal = {Neuroimage},
year = {2002},
month = {11},
volume = {17},
number = {3},
pages = {1117-1130},
abstract = {A fundamental problem of transcranial magnetic stimulation (TMS) is determining the site and size of the stimulated cortical area. In the motor system, the most common procedure for this is motor mapping. The obtained two-dimensional distribution of coil positions with associated muscle responses is used to calculate a center of gravity on the skull. However, even in motor mapping the exact stimulation site on the cortex is not known and only rough estimates of its size are possible. We report a new method which combines physiological measurements with a physical model used to predict the electric field induced by the TMS coil. In four subjects motor responses in a small hand muscle were mapped with 9–13 stimulation sites at the head perpendicular to the central sulcus in order to keep the induced current direction constant in a given cortical region of interest. Input–output functions from these head locations were used to determine stimulator intensities that elicit half-maximal muscle responses. Based on these stimulator intensities the field distribution on the individual cortical surface was calculated as rendered from anatomical MR data. The region on the cortical surface in which the different stimulation sites produced the same electric field strength (minimal variance, 4.2 ± 0.8%.) was determined as the most likely stimulation site on the cortex. In all subjects, it was located at the lateral part of the hand knob in the motor cortex. Comparisons of model calculations with the solutions obtained in this manner reveal that the stimulated cortex area innervating the target muscle is substantially smaller than the size of the electric field induced by the coil. Our results help to resolve fundamental questions raised by motor mapping studies as well as motor threshold measurements.},
web_url = {http://www.sciencedirect.com/science/article/pii/S1053811902912826},
state = {published},
DOI = {10.1006/nimg.2002.1282},
author = {Thielscher A and Kammer T{kammer}}
}

@Article{ 1571,
title = {Phosphene thresholds evoked by transcranial magnetic stimulation are insensitive to short-lasting variations in ambient light},
journal = {Experimental Brain Research},
year = {2002},
month = {8},
volume = {145},
number = {3},
pages = {407-410},
abstract = {Abstract
Transcranial magnetic stimulation applied over the occipital pole is able to induce the perception of light flashes called phosphenes. For phosphene detection and threshold measurement subjects are usually blindfolded or investigated in the dark. The question that we posed here is whether phosphene thresholds change with variations in ambient light. In six subjects we measured thresholds under four different conditions: closed eyes (5 minutes of adaptation) and 0.5, 100, and 3200 cd/m2 background illumination. No systematic change in phosphene thresholds was observed with different lighting conditions. In three subjects we repeated the measurements after one week and again found similar values with no systematic modulation. Our data show that cortical excitability does not change with different light adaptation levels. This confirms that the main adaptation to light takes place at subcortical levels, namely at the retina. The practical conclusion is that it is unnecessary to blindfold subjects when determining phosphene thresholds.},
web_url = {http://link.springer.com/content/pdf/10.1007%2Fs00221-002-1160-3},
state = {published},
DOI = {10.1007/s00221-002-1160-3},
author = {Kammer T{kammer} and Beck S{sbeck}}
}

@Article{ 949,
title = {The influence of current direction on phosphene thresholds evoked by transcranial magnetic stimulation},
journal = {Clinical Neurophysiology},
year = {2001},
month = {11},
volume = {112},
number = {11},
pages = {2015-2021},
abstract = {Objectives: To quantify phosphene thresholds evoked by transcranial magnetic stimulation (TMS) in the occipital cortex as a function of induced current direction.
Methods: Phosphene thresholds were determined in 6 subjects. We compared two stimulator types (Medtronic-Dantec and Magstim) with monophasic pulses using the standard figure-of-eight coils and systematically varied hemisphere (left and right) and induced current direction (latero-medial and medio-lateral). Each measurement was made 3 times, with a new stimulation site chosen for each repetition. Only those stimulation sites were investigated where phosphenes were restricted to one visual hemifield. Coil positions were stereotactically registered. Functional magnetic resonance imaging (fMRI) of retinotopic areas was performed in 5 subjects to individually characterize the borders of visual areas; TMS stimulation sites were coregistered with respect to visual areas.
Results: Despite large interindividual variance we found a consistent pattern of phosphene thresholds. They were significantly lower if the direction of the induced current was oriented from lateral to medial in the occipital lobe rather than vice versa. No difference with respect to the hemisphere was found. Threshold values normalized to the square root of the stored energy in the stimulators were lower with the Medtronic-Dantec device than with the Magstim device. fMRI revealed that stimulation sites generating unilateral phosphenes were situated at V2 and V3. Variability of phosphene thresholds was low within a cortical patch of 2×2 cm2. Stimulation over V1 yields phosphenes in both visual fields.
Conclusions: The excitability of visual cortical areas depends on the direction of the induced current with a preference for latero-medial currents. Although the coil positions used in this study were centered over visual areas V2 and V3, we cannot rule out the possibility that subcortical structures or V1 could actually be the main generator for phosphenes.},
web_url = {http://www.sciencedirect.com/science/article/pii/S1388245701006733},
state = {published},
DOI = {10.1016/S1388-2457(01)00673-3},
author = {Kammer T{kammer}, Beck S{sbeck}, Erb M and Grodd W}
}

@Article{ 40,
title = {Motor thresholds in humans: a transcranial magnetic stimulation study comparing different pulse waveforms, current directions and stimulator types},
journal = {Clinical Neurophysiology},
year = {2001},
month = {2},
volume = {112},
number = {2},
pages = {250-258},
abstract = {Objectives: To evaluate the stimulation effectiveness of different magnetic stimulator devices with respect to pulse waveform and current direction in the motor cortex.
Methods: In 8 normal subjects we determined motor thresholds of transcranial magnetic stimulation in a small hand muscle. We used focal figure-of-eight coils of 3 common stimulators (Dantec Magpro, Magstim 200 and Magstim Rapid) and systematically varied current direction (postero-anterior versus antero-posterior, perpendicular to the central sulcus) as well as pulse waveform (monophasic versus biphasic). The coil position was kept constant with a stereotactic positioning device.
Results: Motor thresholds varied consistently with changing stimulus parameters, despite substantial interindividual variability. By normalizing the values with respect to the square root of the energy of the capacitors in the different stimulators, we found a homogeneous pattern of threshold variations. The normalized Magstim threshold values were consistently higher than the normalized Dantec thresholds by a factor of 1.3. For both stimulator types the monophasic pulse was more effective if the current passed the motor cortex in a postero-anterior direction rather than antero-posterior. In contrast, the biphasic pulse was weaker with the first upstroke in the postero-anterior direction. We calculated mean factors for transforming the intensity values of a particular configuration into that of another configuration by normalizing the different threshold values of each individual subject to his lowest threshold value.
Conclusions: Our transformation factors allow us to compare stimulation intensities from studies using different devices and pulse forms. The effectiveness of stimulation as a function of waveform and current direction follows the same pattern as in a peripheral nerve preparation (J Physiol (Lond) 513 (1998) 571).},
web_url = {http://www.sciencedirect.com/science/article/pii/S1388245700005137},
state = {published},
DOI = {10.1016/S1388-2457(00)00513-7},
author = {Kammer T{kammer}, Beck S{sbeck}, Thielscher A{thielscher}, Laubis-Herrmann U and Topka H}
}

@Article{ 90,
title = {Visual attention and metacontrast modify latency to perception in opposite directions},
journal = {Vision Research},
year = {2000},
month = {4},
volume = {40},
number = {9},
pages = {1027-1033},
abstract = {In human observers, cue-induced visual attention (‘bottom-up‘ transient focal attention) shortens the latency of perception. Metacontrast reduces the
intensity of perception and can even obliterate it. We show that a close relationship exists between both, but that their effects are reversed: cue-induced visual
attention not only shortens latency but also intensifies perception, and metacontrast not only lowers intensity of perception but also prolongs latency. A common
neurophysiological mechanism for both is possible. Indirect evidence suggests that this could be a subthreshold modulation of neuronal thresholds by de- and
hyperpolarization. (C) 2000 Elsevier Science Ltd. All rights reserved.},
web_url = {http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6T0W-3YWWYMX-1-F&_cdi=4873&_user=29041&_orig=browse&_coverDate=04%2F30%2F2000&_sk=999599990&view=c&wchp=dGLbVtb-zSkzV&md5=b75451d15fc097c15841e8319d9f7c8c&ie=/sdarticle.pdf},
state = {published},
DOI = {10.1016/S0042-6989(00)00040-7},
author = {Kirschfeld K{kuno} and Kammer T{kammer}}
}

@Article{ 197,
title = {Phosphenes and transient scotomas induced by magnetic stimulation of the occipital lobe: their topographic relationship},
journal = {Neuropsychologia},
year = {1999},
month = {11},
volume = {37},
number = {2},
pages = {191-198},
abstract = {Transcranial magnetic stimulation (TMS) of the visual cortex is known to induce phosphenes and is able to suppress visual perception. To address the topographic relationship of phosphenes and transient scotomas, the visual field of 10 normal subjects was investigated using a perimetric approach. The central visual field (diameter: 20°) was tested at 32 sites. Perceptual thresholds were determined by presenting 1 ms test spots flashed with varying intensity in random order. TMS was applied with a focal figure-of-eight coil placed over the inion. All subjects perceived phosphenes, mostly restricted to one of the lower quadrants within the visual field. In 13 out of 15 investigations, a magnetic stimulus triggered 100 ms after the visual target resulted in a relative scotoma with threshold changes of 8 dB or more. In 9 of 13 investigations, scotomas coincided spatially with sketches of phosphenes made by subjects in a separate test. Scotomas covered only a small percentage of the total visual field, which may explain the failure of previous studies to find perceptual suppression with the focal coil. The present result demonstrates that phosphenes evoked during TMS can serve as a guide for optimal visual stimulus alignment in neuropsychological experiments.},
web_url = {http://www.sciencedirect.com/science/article/pii/S0028393298000931},
state = {published},
DOI = {10.1016/S0028-3932(98)00093-1},
author = {Kammer T{kammer}}
}

@Article{ 460,
title = {The Fröhlich effect: a consequence of the interaction of visual focal attention and metacontrast},
journal = {Vision Research},
year = {1999},
month = {11},
volume = {39},
number = {22},
pages = {3702-3709},
abstract = {Usually we assume that the central nervous system preserves temporal sequences. Here we show that moving objects—in the context of behaviour often dangerous ones—are seen with a shorter latency than stationary (flashed) objects. In addition moving objects are deblurred. Two mechanisms contribute to this functional specialisation: cue-induced visual focal attention and metacontrast. Under unnatural conditions these mechanisms lead to an optical illusion first described by Fröhlich [Fröhlich, F. W. (1923). Über die Messung der Empfindungszeit. Zeitschrift für Sinnesphysiologie, 54, 58–78].},
web_url = {http://www.sciencedirect.com/science/article/pii/S0042698999000899},
state = {published},
DOI = {10.1016/S0042-6989(99)00089-9},
author = {Kirschfeld K{kuno} and Kammer T{kammer}}
}

@Article{ 198,
title = {Cortical visual processing is temporally dispersed by luminance in human subjects},
journal = {Neuroscience Letters},
year = {1999},
month = {3},
volume = {263},
number = {2-3},
pages = {133-136},
abstract = {Increasing the intensity of a stimulus such as luminance results in faster processing of the signal and therefore decreases simple motor reaction time
(RT). We studied the latencies of visual evoked potentials (VEPs, N80, P100, N130) and RTs in eight subjects to flashing spots of light while varying the
luminance of the spots from 1 to 1000 cd/m(2). The data show that processing time as a function of intensity is modified not only at the retina but also at later
processing sites. This indicates a temporal dispersion of the Visual signal over the whole processing stream from visual input all the way to motor output. (C)
1999 Elsevier Science Ireland Ltd. All rights reserved.},
file_url = {/fileadmin/user_upload/files/publications/pdf198.pdf},
web_url = {http://www.sciencedirect.com/science/article/pii/S0304394099001378},
state = {published},
DOI = {1016/S0304-3940(99)00137-8},
author = {Kammer T{kammer}, Lehr L{lehr} and Kirschfeld K{kuno}}
}

@Article{ 238,
title = {Are recognition deficits following occipital lobe TMS explained by raised detection thresholds?},
journal = {Neuropsychologia},
year = {1998},
month = {11},
volume = {36},
number = {11},
pages = {1161-1166},
abstract = {It is known that transcranial magnetic stimulation (TMS) administered over the occipital pole suppresses recognition of visual objects. Our aim was to ascertain whether this suppression can be interpreted as a change in visual contrast threshold. Four subjects detected the orientation of an U-shaped hook flashed for 21 ms. Under control conditions, mean contrast threshold was found at 0.88 log units Weber contrast. Thresholds were raised if TMS was applied 40–200 ms after the visual stimulus. Maximum elevation was 1.67 log units under TMS at 120 ms stimulus onset asynchrony. This phenomenon can be interpreted as a reduction in signal-to-noise ratio of the visual stimuli by TMS, which can be compensated for by increasing the contrast of the stimuli.},
file_url = {/fileadmin/user_upload/files/publications/pdf238.pdf},
web_url = {http://www.sciencedirect.com/science/article/pii/S0028393298000037},
state = {published},
DOI = {10.1016/S0028-3932(98)00003-7},
author = {Kammer T{kammer} and Nusseck H-G{nusseck}}
}

@Article{ 239,
title = {Repetition blindness in schizophrenic patients},
journal = {European Archives of Psychiatry and Clinical Neuroscience},
year = {1998},
month = {7},
volume = {248},
number = {3},
pages = {136-140},
abstract = {Repetition blindness is the failure to report the detection of repeated items in rapid visually presented lists. It can be explained in terms of either a
processing limitation or an active inhibitory process. In two studies conducted in either English or German language we set out to induce repetition blindness
under various conditions in a total of 47 control subjects and 30 schizophrenic patients. The patients displayed the phenomenon to at least the same degree as
normal control subjects. These results render unlikely accounts of repetition blindness which involve processes known to be dysfunctional in schizophrenic
patients. Moreover, the study provides an example of how the performance of schizophrenic patients can constrain theories of normal cognition.},
file_url = {/fileadmin/user_upload/files/publications/pdf239.pdf},
web_url = {http://www.springerlink.com/content/gg3634rw98vn7trl/fulltext.pdf},
state = {published},
DOI = {10.1007/s004060050030},
author = {Kammer T{kammer}, Saleh F, Oepen G, Manschreck T, Seyyedi S, Kanwisher N and Spitzer M}
}

@Article{ 257,
title = {Functional magnetic resonance imaging of category-specific cortical activation: Evidence for semantic maps.},
journal = {Cognitive Brain Research},
year = {1998},
volume = {6},
pages = {309-319},
abstract = {Functional magnetic resonance imaging (fMRI) was used to examine the pattern of cortical activity during a picture naming task. Subjects (n =
12) had to covertly name either animals or furniture items. Functional scanning was performed using a conventional 1.5-Tesla whole-body MRI system.
Images obtained during naming the two categories were compared using a non-parametric test. The study revealed evidence for domain- specific lexical
regions in left middle, right middle and inferior frontal areas, as well as in superior and middle temporal areas. The results corroborate neuropsychological
data and demonstrate directly and non-invasively in human volunteers that semantic representations in frontal and temporal areas are, to some degree,
localized and possibly implemented as multiple maps. A completely distributed storage of semantic information is rendered unlikely. (C) 1998 Elsevier
Science B.V.},
file_url = {/fileadmin/user_upload/files/publications/pdf257.pdf},
state = {published},
author = {Spitzer M, Kischka U, G\"uckel F, Bellemann ME, Kammer T{kammer}, Seyyedi S, Weisbrod M, Schwartz A and Brix G}
}

@Article{ 256,
title = {Funktionelle Magnetresonanztomographie in der psychopathologischen Forschung.},
journal = {Fortschritte der Neurologie Psychiatrie},
year = {1998},
volume = {66},
pages = {241-258},
abstract = {Mental disorders are characterised by psychopathological symptoms which correspond to functional brain states. Functional magnetic resonance
imaging (fMRI) is used for the non-invasive study of cerebral activation patterns in man. First of all, the neurobiological principles and presuppositions of the
method are outlined. Results from the Heidelberg imaging lab on several simple sensorimotor tasks as well as higher cognitive functions, such as working and
semantic memory, are then presented. Thereafter, results from preliminary fMRI studies of psychopathological symptoms are discussed, with emphasis on
hallucinations, psychomotoric phenomena, emotions, as well as obsessions and compulsions. Functional MRI is limited by the physics underlying the method,
as well as by practical constraints regarding its use in conjunction with mentally ill patients. Within this framework, the problems of signal-to-noise ratio,
data analysis strategies, motion correction, and neurovascular coupling are considered. Because of the rapid development of the field of fMRI, maps of higher
cognitive functions and their respective pathology seem to be coming within easy reach.},
state = {published},
author = {Spitzer M, Kammer T{kammer}, Bellemann ME, Brix G, Layer B, Maier S, Kischka U and G\"uckel F}
}

@Article{ 365,
title = {Functional MR imaging of the prefrontal cortex: Specific activation in a working memory task},
journal = {Magnetic Resonance Imaging},
year = {1997},
month = {9},
volume = {15},
number = {8},
pages = {879-889},
abstract = {Functional magnetic resonance imaging was used to identify cortical regions activated by a working memory task involving letter detection. Twenty four normal subjects were scanned with a conventional 1.5-T magnet while performing one of two tasks: In the activation task, subjects responded by pressing a button whenever any presented letter was the same as the second last in the sequence. In the control condition, subjects had to respond to a single predefined letter without memory update requirments. The activation task and the control condition were identical with regard to perceptual input and motor output. They were different only regarding the task demand. Movement artifacts were minimized in a two way strategy and eight subjects were excluded from further analysis. Functional MR data from the remaining 16 subjects were analyzed on the basis of anatomical regions-of-interest which were manually defined in each subject. The engagement of working memory produced significant activation in the dorsolateral prefrontal cortex (Brodmann's areas 9, 10, 46, and 47) in both hemispheres. Results demonstrate the applicability of the paradigm within a clinical MRI setup and corroborate previous findings of non-lateralized dorsolateral prefrontal activation during continuous context updating and active maintenance.},
file_url = {/fileadmin/user_upload/files/publications/pdf365.pdf},
web_url = {http://www.sciencedirect.com/science/article/pii/S0730725X97000210},
state = {published},
DOI = {10.1016/S0730-725X(97)00021-0},
author = {Kammer T{kammer}, Bellemann ME, Gl\"uckel F, Brix G, Gass A, Schlemmer H and Spitzer M}
}

@Article{ 538,
title = {Combining neuroscience research methods in psychopathology},
journal = {Current Opinion in Psychiatry},
year = {1996},
month = {9},
volume = {9},
number = {5},
pages = {352-363},
abstract = {The advent of new neuroscience tools for the noninvasive study of the living brain pushed psychopathology beyond previously existing limits.Some of these tools, such as positron emission tomography, have been used within psychiatry for a while, whereas others such as functional magnetic resonance imaging, high resolution event-related potentials and magnetoencephalography are beginning to be used. Still others, such as transcranial magnetic stimulation, may not only be used as a mapping and diagnostic tool but may eventually even have therapeutic uses. This review briefly describes the methods and some recent findings pertaining to basic issues in psychopathology. When the high spatial resolution of imaging techniques is combined with the high temporal resolution of electrophysiological and magnetic techniques, these methods provide enough detail for the study of brain structures related to the processing of high-level (meaningful) information and thereby have the potential to produce major contributions to psychopathology in the near future.},
web_url = {http://journals.lww.com/co-psychiatry/Abstract/1996/09000/Combining_neuroscience_research_methods_in.12.aspx},
state = {published},
author = {Spitzer M and Kammer T{kammer}}
}

@Article{ 950,
title = {Dopaminergic modulation of semantic network activation},
journal = {Neuropsychologia},
year = {1996},
volume = {34},
pages = {1107-1113},
abstract = {In order to examine the effect of dopamine on semantic processing, we performed a double-blind, placebo-controlled study. Healthy volunteers (n = 31) were tested in a lexical decision paradigm after ingestion of either L-dopa 100 mg with benserazide 25 mg or placebo. While direct semantic priming was influenced only marginally by L-dopa, the indirect priming effect was reduced significantly. These data support the hypothesis that dopamine increases the signal-to-noise ratio in semantic networks by reducing the spread of semantic processing, thereby leading to a focussing of activation. Copyright (C) 1996 Elsevier Science Ltd.},
file_url = {/fileadmin/user_upload/files/publications/pdf950.pdf},
state = {published},
author = {Kischka U, Kammer T{kammer}, Weisbrod M, Maier S, Thimm M and Spitzer M}
}

@Inbook{ KammerK2006,
title = {Manifestationen von Frontalhirnschädigungen},
year = {2006},
pages = {489-500},
abstract = {Die Neuropsychologie hat verschiedene kognitive Model-
le entwickelt, die auf der Annahme basieren, dass der
frontale Kortex die »höchsten« integrativen Leistungen,
die der Mensch auszuführen vermag, steuert und kontrol-
liert. Dieser Vorstellung ent sprechend weisen Patienten
mit Schädigungen des Frontalhirns (und zumeist zusätz-
lich auch Teilen anderer kortikaler und subkortikaler Areale)
Störungen der »Exekutivfunktionen« auf. Diese betreffen
das Planen, Problemlösen, die Initiierung und Inhibi tion
von Handlungen sowie die Handlungskontrolle. Damit
eng assoziiert ist die Funktion des
Arbeitsgedächtnisses.
Für das Auftreten exekutiver Dysfunktionen scheint ent-
scheidend zu sein, dass die jeweilige Situation ohne eine
fest vorgegebene Struktur ist und die Organisation und
das Planen des Verhaltens über einen längeren Zeitraum
bei gleichzeitiger Berücksichtigung mehrerer Teilaspekte
(»multitasking«) erforderlich macht. Patienten mit aus-
geprägten Störungen exekutiver Funktionen wirken oft
interessenlos und gleichgültig. Ihre Handlungen scheinen
nicht durch Ziele mo tiviert und geordnet zu sein. Die Fähig-
keit ab schätzen zu können, mit Hilfe welcher Teilschritte ein
übergeordnetes Ziel erreicht werden kann, ist vermindert.
Den Patienten fällt es schwer, bereits gefasste Pläne auf-
grund eingetretener Veränderungen zu modifizieren und
inadäquate Handlungen zu unterdrücken. Die Kranken kön-
nen da rüber hinaus ein Missachten der Instruktionen zur
Durchführung von Aufgaben (»rule-breaking«), eine Bein-
trächtigung von Antizipationsprozessen wie auch perseve-
ratives und rigides Verhalten aufweisen. Es scheint möglich,
dass diese Störungen in ihrer Summe die immer wieder bei
Patienten mit präfrontalen Läsionen zu beobachtenden
Änderungen der Gesamtpersönlichkeit ausmachen. Die
»Wesensänderungen« der Patienten betref fen den Antrieb,
die Emotionalität sowie das Sozial verhalten.},
web_url = {http://link.springer.com/content/pdf/10.1007%2F3-540-28449-4_45},
editor = {Karnath, H.-O. , P. Thier},
publisher = {Springer},
address = {Berlin, Germany},
edition = {2.},
booktitle = {Neuropsychologie},
state = {published},
ISBN = {3-540-28449-4},
DOI = {10.1007/3-540-28449-4_45},
author = {Kammer T{kammer}{Department Human Perception, Cognition and Action} and Karnath H-O}
}

@Inbook{ 1618,
title = {Manifestationen von Frontalhirnschädigungen},
year = {2003},
pages = {515-528},
editor = {Karnath, H.-O. , P. Thier},
publisher = {Springer},
address = {Berlin, Germany},
booktitle = {Neuropsychologie},
state = {published},
ISBN = {3-540-67359-8},
author = {Karnath H-O and Kammer T{kammer}}
}

@Poster{ ThielscherK2003,
title = {Determining the cortical stimulation site in TMS: Linking
physiological measurements with physical field models},
year = {2003},
month = {6},
volume = {29},
pages = {1168},
abstract = {We report a novel method to determine the site and size of stimulated cortical area in
TMS. Applied to the motor cortex, it allows to determine the likely cortical representation
of muscles. Up to now, the most common procedure for this is motor mapping. In
motor mapping, the obtained two-dimensional distribution of coil positions with associated
muscle responses is used to calculate a center of gravity on the skull. However,
classical mapping does not allow to determine the exact stimulation site on the cortex
and only rough estimates of its size are possible. Our method combines physiological
measurements with a physical model used to predict the electric field induced by the
TMScoi l to overcome these limitations. In four subjects motor responses in a small
hand muscle were mapped with 9 - 13 stimulation sites at the head perpendicular to the
central sulcus in order to keep the induced current direction constant in a given cortical
region of interest. Input-output functions from these head locations were used to determine
stimulator intensities that elicit half-maximal muscle responses. Based on these
stimulator intensities the field distribution on the individual cortical surface was calculated
as rendered from anatomical MR data. The region on the cortical surface in which
the different stimulation sites produced the same electric field strength (minimal variance
4.2 ± 0.8 %. ) was determined as the most likely stimulation site on the cortex. In all
subjects, it was located at the lateral part of the hand knob in the motor cortex. Comparisons
of model calculations with the solutions obtained in this manner reveal that the
stimulated cortex area innervating the target muscle is substantially smaller than the size
of the electric field induced by the coil.},
web_url = {http://www.neuro.uni-goettingen.de/nbc.php?sel=archiv},
event_name = {29th Göttingen Neurobiology Conference},
event_place = {Göttingen, Germany},
state = {published},
author = {Thielscher A{thielscher}{Department High-Field Magnetic Resonance} and Kammer T{kammer}{Department Human Perception, Cognition and Action}}
}

@Poster{ 1645,
title = {Is there domain specificity in prefrontal working memory areas? An event-related fMRI-study},
year = {2002},
month = {7},
volume = {3},
number = {009.13},
abstract = {Objective:
The segregation of visual processing into a dorsal and a ventral stream is well established for posterior cortex. It is unclear, however, whether this segregation can also be found in frontal cortical areas, involved in working memory function. Most of the previous imaging experiments comparing activation patterns for memory of objects and memory for spatial locations failed to demonstrate a clear dissociation in prefrontal areas. An explanation for these failures could be that the objects used in these studies may not be specific enough for the ventral stream, due to their spatial properties being processed in the dorsal stream too. To avoid this confusion, we set up an experiment comparing working memory for colors, as a specific indicator for the ventral stream, with working memory for spatial information.
Method:
In a delayed-match-to-sample task, subjects were presented with four dots of different colors (first modality) in a certain spatial configuration (second modality). To suppress verbal coding of the colors, letters were shown within the dots and had to be memorized as a third modality. Before each trial, subjects were instructed as to which two of the three modalities they had to memorize. Event-related fMRI data were analysed with BrainVoyager on an intra- and intersubject level.
Result:
A conjunction analysis identified areas that were specifically active while subjects had to maintain colors and different areas of spatial locations. Areas active during color memory were mainly located in the medial frontal gyrus while premotor areas were activated during spatial memory. A connectivity analyis showed that activation profiles from a color area covaried with activity in ventral occipito-temporal regions, whereas activation profiles from a spatial area covaried with activity in superior-parietal regions.
Conclusion:
Our data support the hypothesis of a domain-specific segregation of frontal areas involved in working memory.},
web_url = {http://fens2002.neurosciences.asso.fr/pages/posters/R1/A009_13.html},
event_name = {3rd Forum of European Neuroscience (FENS 2002)},
event_place = {Paris, France},
state = {published},
author = {Saur R{saur}{Department Human Perception, Cognition and Action}, Erb M, Grodd W and Kammer T{kammer}{Department Human Perception, Cognition and Action}}
}

@Poster{ 1644,
title = {Spatial working memory: how to measure accuracy of performance},
year = {2002},
month = {7},
volume = {3},
number = {009.8},
abstract = {In working memory tests, performance is normally assessed in terms of error rates. This is often a crude simplification, especially if testing memory for sequences. We thus developed a method to measure accuracy of performance in a spatial working memory task.
Method: 
Objective:
In working memory tests, performance is normally assessed in terms of error rates. This is often a crude simplification, especially if testing memory for sequences. We thus developed a method to measure accuracy of performance in a spatial working memory task.
Method:
Twelve subjects looked at a computer screen which was divided into four quadrants, 11.5 x 11.5 ° each. In a delayed-response design, subjects were presented with a sequence of one to six dots, each appearing in a random location within one of the four quadrants. After a delay of 5 s, subjects had to reproduce the sequence of the dots as accurately as possible using a joystick. We analysed both the correctness of the sequence (correct quadrant) and the accuracy of the remembered spatial location of each dot. For sequence analysis a modified Levenshtein algorithm was implemented. This algorithm evaluated deletions, insertions, substitutions in the sequences as well as swaps and calculated a correctness term (interval scale).
Result:
A pronounced load effect occurred for both correctness of sequences and spatial accuracy. Sequence performance declined with increasing load in an exponential fashion. At load 6, only 32% of the sequences were reproduced without error. The Levensthein correctness term dropped from 100% to 58% only. Spatial accuracy decreased linearly with increasing load from 0.75° (load 1) to 2.7° (load 6).
Conclusion:
The experimental design allows a quantitative approach to working memory performance on a high resolution scale. The Levenshtein algorithm is a promising tool for any sequence analysis problem in psychological tests.},
web_url = {http://fens2002.neurosciences.asso.fr/pages/posters/R1/A009_8.html},
event_name = {3rd Forum of European Neuroscience (FENS 2002)},
event_place = {Paris, France},
state = {published},
author = {Kammer T{kammer}{Department Human Perception, Cognition and Action}, Saur R{saur}{Department Human Perception, Cognition and Action} and Scharnowski F{franks}}
}

@Poster{ Kammer2002,
title = {Multimodales Mapping des visuellen Kortex mit funktioneller Magnetresonanztomographie und transkranieller Magnetstimulation},
journal = {Experimentelle Psychologie},
year = {2002},
month = {3},
volume = {44},
pages = {67},
abstract = {Transkranielle Magnetstimulation (TMS) über dem Hinterkopf kann die Wahrnehmung von
Phosphenen hervorrufen. Sie erscheinen als kurz aufblitzende, grau-weisse Linien, Seg-mente
oder wolkenhafte Gebilde. Bei unveränderter Spulenposition sind Ort und Erschei-nungsform
recht konstant, so dass Versuchspersonen sie zeichnen können. Sie erscheinen hauptsächlich im
unteren Gesichtsfeld, uni- oder bilateral, mit einer lateralen Ausdehnung von 1-5° und bevorzugt
an parafovealen Orten zwischen 1° und 20° Exzentrizität. Bei stärkerer Stimulationsintensität
wird die Fovea mit einbezogen. Um den potentiellen Stimulationsort zu charakterisieren, wurde
mittels fMRT eine individuelle kortikale Karte der Retinotopie, mit Exzentrizität und
Polarwinkel erstellt. Eine stereotaktische Positionierungsanlage ermöglicht die Projektion der
TMS-Stimulations-Orte direkt in das individuelle anatomische und funktio-nelle MR-Bild. Es
zeigt sich, dass sich Phosphene sowohl mit Spulenpositionen über V1 als auch über V2 und V3
auslösen lassen. Selten folgt der subjektive Ort des Phosphenes der in der fMRT gemessenen
retinotopen Karte. Wahrscheinlich werden, unabhängig von der Spulenposition, Phosphene
immer in V1 generiert.},
web_url = {http://www.tu-chemnitz.de/hsw/psychologie/forschung/teap2002/poster.html},
event_name = {44. Tagung Experimentell Arbeitender Psychologen (TeaP 2002)},
event_place = {Chemnitz, Germany},
state = {published},
author = {Kammer T{kammer}{Department Human Perception, Cognition and Action}}
}

@Poster{ 1643,
title = {Wie kann man räumliches Arbeitsgedächtnis exakt vermessen?},
journal = {Experimentelle Psychologie},
year = {2002},
month = {3},
volume = {44},
pages = {193},
abstract = {Es wird eine Working-Memory-Aufgabe vorgestellt, die beim funktionalem Mapping (fMRI,
TMS) und in der klinisch-neuropsychologischen Praxis eingesetzt werden soll. Auf einem
Bildschirm wurden mehrere Punkte sequentiell dargeboten, die sich die Versuchsperson fünf
Sekunden lang merken musste. Nach der Retentionsphase sollten dann die Positionen der Punkte
in vorgegebener Reihenfolge mit einem Joystick markiert werden. Die Anzahl der Punkte wurde
zwischen 1 und 6 variiert (Load), um den Einfluss des Loads auf Sequenzwiedergabe und
Positionspräzision zu überprüfen. Die Analyse von Sequenzfehlern erfolgte über die
Levenshtein-Metrik, einem Verfahren, dass erlaubt, Auslassungen, Einfügungen und
Vertauschen zu erkennen. Erwartungsgemäß steigt mit dem Load die Anzahl von
Sequenzfehlern und die mittlere Abweichung zwischen gezeigten und wiedergegebenen
Positionen der Punkte. Interessanterweise betrifft die Verschlechterung der räumlichen
Wiedergabeleistung alle Items einer Sequenz in ähnlicher Weise. Der Algorithmus für die
Sequenzanalyse erweitert die Auflösung zwischen falsch und richtig bei der Bewertung von
Sequenzwiedergaben und ermöglicht die Analyse spezifischer Fehler.},
web_url = {http://www.tu-chemnitz.de/hsw/psychologie/forschung/teap2002/poster.html},
editor = {Baumann, M.; Keinath, A.; Krems, J. F.},
event_name = {44. Tagung Experimentell Arbeitender Psychologen (TeaP 2002)},
event_place = {Chemnitz, Germany},
state = {published},
author = {Saur R{saur}, Scharnowski F{franks} and Kammer T{kammer}}
}

@Poster{ 1581,
title = {Der Flash-lag Effekt: Lässt sich eine neuronale Latenzdifferenz für die Wahrnehmung bewegter und geblitzter visueller Reize mit TMS nachweisen?},
year = {2002},
month = {2},
volume = {5},
pages = {71},
abstract = {Ein sich bewegendes Objekt in der Außenwelt unterliegt durch neuronale Laufzeiten von
der Retina bis zur bewussten Wahrnehmung ebenso einer Latenzzeit wie ein geblitztes.
Wenn man jedoch an räumlich korrespondierender Stelle zu einem bewegten Stimulus
einen zweiten blitzt, dann wird der geblitzte als zurückliegend wahrgenommen; ein
Effekt, der als “flash-lag effect” (FLE) bekannt wurde (Nijhawan 1994). Eines der Erklärungsmodelle
beruht auf unterschiedlichen visuellen Wahrnehmungslatenzen. Wir verwendeten
die transkranielle Magnetstimulation (TMS) über dem okzipitalen Kortex, um
Laufzeitunterschiede bewegter und geblitzter Stimuli nachzuweisen.
Drei Versuchspersonen gaben in einem ersten psychophysischen Experiment durch
Tastendruck (2AFC) an, ob sie eine sich horizontal bewegende Linie links oder rechts
von einer geblitzten gesehen hatten. Im zweiten Experiment wurde untersucht, zu welchem
Zeitpunkt TMS die visuelle Verarbeitung der geblitzten Linie stört (temporaler
2AFC, t2AFC). Im dritten Experiment wurde die Wahrnehmung der bewegten Linie mit
TMS maskiert (t2AFC). Dazu wurde diese kurz ausgeblendet, wodurch in der Trajektorie
eine Lücke entstand, die das zu störende Ereignis darstellte.
Im ersten Experiment fanden wir einen FLE von über 70ms (73,6ms - 83,6ms). Die
Wahrnehmung der geblitzten Linie wurde durch TMS mit einer SOA zwischen 75 und
125ms gestört. Mit bewegten Stimuli ergab sich ein Maximum der Maskierung durch
TMS ebenfalls zwischen 75 und 125ms SOA.
In den bisher durchgeführten Messungen lässt sich mit TMS über dem visuellen Kortex
kein Laufzeitunterschied für geblitzte und bewegte Objekte nachweisen. Dies deutet entweder
darauf hin, dass eine Latenzdifferenz erst auf einer höheren Verarbeitungsebene
entsteht, oder dass dem “flash-lag effect” ein anderer Mechanismus zugrunde liegt.},
web_url = {http://www.twk.tuebingen.mpg.de/twk02/},
editor = {Bülthoff, H. H.; Gegenfurtner, K. R.; Mallot, H. A.; Ulrich, R.},
event_name = {5. Tübinger Wahrnehmungskonferenz (TWK 2002)},
event_place = {Tübingen, Germany},
state = {published},
author = {Vorwerg M{vorwerg} and Kammer T{kammer}}
}

@Poster{ 1580,
title = {Gibt es doch eine modalitätspezifsche Segregation des
präfrontalen Kortex?: Eine fMRI-Studie},
year = {2002},
month = {2},
volume = {5},
pages = {202},
abstract = {Für den retrorolandischen Kortex gilt die Dissoziation in ein raum- sowie bewegungsverarbeitendes
dorsales Projektionssystem und ein objekt- sowie farbspezifisches ventrales
Projektionssystem als gut elaboriert. Inwieweit die beiden Projektionssysteme ihre Aufteilung
im prärolandischen, insbesondere präfrontalen Kortex fortsetzen, ist aber noch
strittig. Eine typische Funktion des präfrontalen Kortex ist das Arbeitsgedächtnis, d. h.
die Aufrechterhaltung und Verarbeitung von Informationen zur Verhaltensplanung.
Untersuchungen, die eine Segregation von raum- und objektspezifischen Arealen im präfrontalen
Kortex für das Arbeitsgedächtnis nachweisen wollten, sind häufig gescheitert.
Tatsächlich sind aber Objekte als spezifischer Indikator für den ventralen Projektionsstrom
nur bedingt geeignet, da Objekte in der Regel auch in ihrer einfachsten Form räumliche
Landmarken besitzen oder aus einzelnen, räumlich verknüpften Elementen bestehen.
In der vorliegenden event-related fMRI-Studie wurde daher dem raumspezifischen
Arbeitsgedächtnis das Memorieren von Farben als Spezifität des ventralen Stroms gegenüber
gestellt.
Während der fMRI-Messung wurden den Versuchspersonen mehrere Punkte in bestimmter
räumlicher Anordnung und unterschiedlicher Farbe gezeigt. Als dritte Modalität wurden
zur Suppression der verbalen Kodierung der Farbe zusätzlich Buchstaben in den
Punkten integriert. In insgesamt drei unterschiedlichen Experimental-Bedingungen
wurde der Versuchsperson über eine Anweisung mitgeteilt, welche zwei der drei Modalitäten
sie sich für eine Zeitdauer von fünf Sekunden merken sollte.
Mittels Konjunktionsanalysen wurde die spezifische Aktivierung der einzelnen Modalitäten
während der Merkphase bestimmt. Bei vier von sechs Versuchspersonen zeigten sich
prärolandisch Dissoziationen zwischen farb- und raumspezifischen Arealen. Farbspezifische
Areale wurden insbesondere entlang des Gyrus frontalis medius identifiziert, während
raumspezifische Regionen überwiegend im prämotorischen Kortex entdeckt wurden.
Konnektivitätsanalysen ergaben, dass Aktivierungsverläufe aus dem prämotorischen
Kortex tatsächlich stärker mit der Aktivität in superior-parietalen Arealen kovariieren
(dorsales Projektionssystemen), Aktivierungsverläufe aus farbspezifischen präfrontalen
Arealen dagegen mit der Aktivierung im Bereich des Gyrus fusiformis (ventrales Projektionssystem).
Die Ergebnisse stärken die Hypothese einer tendenziell modalitätsspezifischen Segregation
im prärolandischen Kortex, zwischen dorsolateralen präfrontalen und prämotorischen
Arealen.},
web_url = {http://www.twk.tuebingen.mpg.de/twk02/},
editor = {Bülthoff, H. H.; Gegenfurtner, K. R.; Mallot, H. A.; Ulrich, R.},
event_name = {5. Tübinger Wahrnehmungskonferenz (TWK 2002)},
event_place = {Tübingen, Germany},
state = {published},
author = {Saur R{saur}, Erb M, Grodd W and Kammer T{kammer}}
}

@Poster{ 1582,
title = {Maskierung visueller Reize durch Magnetstimulation in zwei Zeitperioden},
year = {2002},
month = {2},
volume = {5},
pages = {86},
abstract = {Transkranielle Magnetstimulation (TMS) über dem Hinterkopf erhöht die Kontrast-
Wahrnehmungsschwelle für geblitze visuelle Reize (Kammer & Nusseck 1998). Neben
dem bekannten Zeitintervall mit einer SOA von +100 ms gibt es Hinweise, daß es eine
bis zwei frühere Perioden innerhalb der visuellen Reizverarbeitung gibt, die durch TMS
gestört werden können (Corthout et al 1998, 1999, 2000). Das erste Maximum wird im
Bereich von 70 ms SOA beschrieben (TMS vor visuellem Reiz!), daß zweite zwischen 35
und +45 ms SOA. Bisher ist nicht klar, ob es sich bei diesen frühen Perioden um kortikale
Effekte oder um nicht-kortikale Einflüsse der TMS handelt.
Die Versuchspersonen mussten eine einfache Diskriminierungsaufgabe zu einem geblitzten
Objekt ausführen (Wahlpflichtaufgabe mit 4 Alternativen). Die Modulation der Kontrastwahrnehmungsschwelle
durch TMS wurde für zwei Hintergrundhelligkeiten (0.3
und 3 cd/m2) und mehrere TMS-Intensitäten in einem Zeitfenster von -100 ms bis +200
ms SOA ermittelt.
Bei allen fünf Versuchspersonen fand sich eine ausgeprägte Zunahme der Kontrast-
Wahrnehmungsschwelle im Zeitfenster zwischen +75 und +145 ms SOA. Zusätzlich
zeigten vier von fünf Versuchspersonen eine weniger stark ausgeprägte Schwellenanhebung
in einem zweiten Zeitintervall zwischen 35 und +45 ms SOA. Mit stärkerer TMSIntensität
nahmen beide Modulationen zu. Bei dunklem Hintergrund war die relative
Schwellenzunahme (Weber-Kontrast) größer als bei hellem Hintergrund und die Maxima
der Modulation traten bei späteren SOA auf.
Die Abhängigkeit des TMS-Maskierungseffektes von der Hintergrundluminanz im Zeitfenster
+100 ms SOA spiegelt die visuelle Übertragungszeit wieder und spricht für einen
kortikalen Ursprung. Die von Corthout beschriebene Maskierung mit früheren TMS SOA
lässt sich mit stärkeren TMS-Intensitäten reproduzieren. Da sich das Maximum der
Modulation für diesen Effekt etwa bei 0 ms SOA befindet, erscheint ein unspezifischer,
nicht-kortikaler TMS-Effekt, z.B. Irritation durch den akustischen Artefakt plausibel.},
web_url = {http://www.twk.tuebingen.mpg.de/twk02/},
editor = {Bülthoff, H. H.; Gegenfurtner, K. R.; Mallot, H. A.; Ulrich, R.},
event_name = {5. Tübinger Wahrnehmungskonferenz (TWK 2002)},
event_place = {Tübingen, Germany},
state = {published},
author = {Puls K{puls} and Kammer T{kammer}}
}

@Poster{ 963,
title = {TMS field model links physics and physiology},
year = {2001},
month = {11},
volume = {31},
number = {401.14},
abstract = {Stereotactic positioning devices allow to exactly navigate the position of a TMS coil with respect to the individual cortical architecture. However, the exact stimulation site and the size of the neuronal pool stimulated still remain unknown. We used a common spherical model to predict the cortical stimulation site in the motor system. In 4 subjects motor responses were registered in a small hand muscle. A stereotactic positioning system allowed to measure continually the position of the figure-of-eight coil with respect to the individual cortical anatomy visualized in an anatomical 3d MRI scan. The coil was oriented perpendicular to the central sulcus and a hot spot was determined. Then motor responses were measured at several stimulation sites from threshold levels up to maximal responses, increasing stimulus intensity in steps of 10% (input-output function). The stimulation sites were placed in a line perpendicular to the central sulcus. With maximal stimulation intensity motor responses were obtained about 5 cm apart from the hot spot. For each stimulation site a sigmoidal function was fitted to the input-output data and the stimulation intensity for half-maximal motor responses was calculated. The distribution of the electric field strength was calculated on the cortical surface for each site using the spherical model. Finally, the region on the cortical surface was calculated where all different stimulation sites produced the same electric field strength (variance < 7%). In all subjects that region was found within the hand knob of the precentral gyrus. Using the field model a prediction of the effective field strength is possible.},
web_url = {http://www.sfn.org/index.aspx?pagename=abstracts_ampublications},
event_name = {31st Annual Meeting of the Society for Neuroscience (Neuroscience 2001)},
event_place = {San Diego, CA, USA},
state = {published},
author = {Kammer T{kammer} and Thielscher A{thielscher}}
}

@Poster{ 64,
title = {Discrimination is determined by detection: a TMS study of visual perception},
year = {2001},
month = {3},
pages = {63},
abstract = {If a stimulus is followed by a mask performance often strongly deteriorates. However, detection tasks are usually less affected than discrimination tasks. For example, existence versus non-existence of a masked vernier can more easily be judged than disrimination between the left and right offsets. Magnetic pulses of transcranial magnetic stimulation(TMS) applied at the occipital cortex are known to act like visual masks. Here, we investigate whether or not detection and discrimination tasks show identical time courses under TMS stimulation using vernier stimuli.
We presented vertical verniers, 1200" long with a vertical gap of 60", to one of the lower visual quadrants. A fixation dot was permanently present during a stimulus presentation. Distance between vernier and fixation dot was 1272''. Stimuli were displayed for 20ms on an analog monitor controlled by a Power Macintosh computer via fast 16 bit D/A converters (1MHz pixel rate). Luminance of the stimuli was 2 cd/m2 and luminance of the background smaller than 0.01 cd/m2. In a temporal 2AFC detection task a vernier was flashed in either one of two subsequent intervals which always began with the presentation of the fixation dot. Subjects were asked to indicate the interval containing the vernier and correct reponses were determined. In the discrimination task subjects had to indicate the direction of vernier offset (left or right). Thresholds were determined using an adaptive strategy (PEST). TMS pulses were applied to the occipital cortex. Maintenance of the coil position was monitored using a stereotactic positioning device. In the experiments the independent variable is the SOA between vernier onset and TMS pulse.
Performance for all three subjects was well in the hyperacuity range, i.e. between 11'' and 50'' if no TMS was applied. TMS shifted discrimination thresholds to higher values in dependence of the SOA in the typical U-shaped manner. Depending on observer, the maximal modulation was reached between 100 ms and 130 ms SOA. With these SOAs discrimination was strongly deteriorated and sometimes even impossible. Similarly, detection of the vernier was modulated by TMS in a U-shaped manner. Chance level (50% correct responses) was reached between 100 ms and 130 ms, too. In both tasks only one narrow peak of deterioration was found.
TMS applied over the occipital lobe strongly modulates visual detection as well as visual discrimination. Since the time courses of modulation of detection and discrimination tasks do not differ, we suggest that in the early cortical visual system both processes have an identical temporal structure. Discrimination processes do not require a longer processing time. The data suggest that both perceptual qualities are based on the same signal process in the early visual system.},
web_url = {http://www.twk.tuebingen.mpg.de/twk01/Pkontrast.htm},
event_name = {4. Tübinger Wahrnehmungskonferenz (TWK 2001)},
event_place = {Tübingen, Germany},
state = {published},
author = {Kammer T{kammer} and Herzog M}
}

@Poster{ 964,
title = {Where do we stimulate the brain? A TMS study using a stereotactic positioning device},
year = {2000},
month = {11},
volume = {30},
number = {550.17},
abstract = {Transcranial magnetic stimulation (TMS) of the brain with a figure-of-eight coil causes a focal stimulation of the cortical surface. However, the exact stimulation site with respect to the coil is not yet clear. In an isolated peripheral nerve preparation not the electric field maximum in the center of the coil causes the excitation but rather the negative spatial derivative some millimeters besides the maximum (Maccabee 93). In the cortex, on the other hand, it has been argued that the field maximum itself causes the depolarization due to bend in the axons (Amassian 92). The visual and motor cortex in three subjects was mapped with monophasic pulses and two current directions. Coil positions, i.e. midpoint at the junction of the two coil windings relative to the head were monitored online and registered with a custom-made stereotactic measuring device with a precision of ± 1 mm. Subjects reported the site and size of phosphenes in the visual field that were evoked by stimulating the occipital lobes (horizonal current directions). A phosphene map from different stimulation sites was measured with a highly reproducible vertical region above the inion where subjects reported phosphenes in the left and right visual field. Reversing the current of the coil shifted the zone of bilateral phosphenes horizontally by about 10 mm. In the motor cortex a similar shift was found in a center-of-gravity map determined for a small hand muscle (current directions perpendicular to the central sulcus). The data show that the focus of depolarization in the cortex, like that in the peripheral nerve, is not under the midpoint of the coil but shifted towards the negative spatial derivative of the induced electric field.},
web_url = {http://www.sfn.org/annual-meeting/past-and-future-annual-meetings/abstract-archive},
event_name = {30th Annual Meeting of the Society for Neuroscience (Neuroscience 2000)},
event_place = {New Orleans, LA, USA},
state = {published},
author = {Kammer T{kammer}}
}

@Poster{ 121,
title = {Mapping the visual cortex with stereotactic TMS and functional MRI},
journal = {Perception},
year = {2000},
month = {8},
volume = {29},
number = {ECVP Abstract Supplement},
pages = {67},
abstract = {Focal transcranial magnetic stimulation (TMS) is able to elicit phosphenes when applied over the occipital pole. The aim of this study was to test whether the site of the phosphenes in the visual field is linked to the retinotopic map of the visual cortex.
In four subjects we determined the individual retinotopy of the visual field by means of a dynamic mapping technique (eccentricity and polar angle) with functional MRI. Then we used focal TMS to register phosphene sites with different coil positions. These positions were monitored with respect to the head by a custom-made stereotactic measuring device. At each stimulation position, the subject drew the perceived phosphene directly on a touch screen.
Phosphenes were reproducibly elicited not only from positions corresponding to V1 but also from extrastriate areas V2 - V4. The general appearance of the phosphenes did not change with the visual area. In all subjects, displacement of the coil from a cortical position which represents the fovea to a position of more peripheral representation displaced the phosphene from the centre of the visual field towards the periphery. Our data demonstrate that stereotactic TMS can be used to create a detailed map of the visual cortex.},
web_url = {http://www.perceptionweb.com/abstract.cgi?id=v000207},
event_name = {23rd European Conference on Visual Perception (ECVP 2000)},
event_place = {Groningen, Netherlands},
state = {published},
author = {Kammer T{kammer}, Erb M, Beck S and Grodd W}
}

@Poster{ 132,
title = {Masking visual stimuli by transcranial magnetic stimulation: Comparison with masking by light},
journal = {Perception},
year = {2000},
month = {8},
volume = {29},
number = {ECVP Abstract Supplement},
pages = {97},
abstract = {Transcranial magnetic stimulation (TMS) applied over the occipital pole is able to suppress the perception of visual stimuli. This suppression is based on a shift of the perception threshold. Here we compared the modulatory effect of a light flash with the suppression effect of TMS.
Subjects had to report the orientation of a flashed hook. At two different adaptation levels (0.3 and 3 cd m-2) we determined contrast thresholds by the method of constant stimuli. A light flash (15 or 150 cd m-2 for the different adaptation levels) was applied with different SOAs after the appearance of the hook, and threshold shifts were measured. Similarly, threshold shifts due to focal TMS with SOAs from -25 to +195 ms were measured.
With high background intensity, TMS shifted thresholds up to 1.2 Weber contrast units (WC), and with low background intensity the shift was up to 6.6 WC. Latency for the maximal effect was shorter at the high background level (85 ms SOA) than at the lower level (115 ms SOA). We found similar effects on threshold shifts with light flashes at SOAs from 20 to 80 ms. Our results suggest that the masking effect of TMS might share similar mechanisms with a masking effect by light.},
web_url = {http://www.perceptionweb.com/abstract.cgi?id=v000302},
event_name = {23rd European Conference on Visual Perception (ECVP 2000)},
event_place = {Groningen, Netherlands},
state = {published},
author = {Puls K{puls} and Kammer T{kammer}}
}

@Poster{ 126,
title = {Dipollokalisationen beim Schachbrett-VEP: Abhängigkeit von räumlicher Frequenz und Stimulationsort im Gesichtsfeld},
year = {2000},
month = {2},
pages = {77},
abstract = {Die Latenz visuell evozierter Potentiale (VEP), die durch Kontrastumkehr erzeugt werden,
variiert in Abhängigkeit von der räumlichen Frequenz des Schachbrettmusters. Aufgrund
der unterschiedlichen Größen der rezeptiven Felder werden feine Muster eher
foveal verarbeitet und haben eine verzögerte P1 im Vergleich zu groben Mustern, die eher
parafoveal verarbeitet werden. Mit der vorliegenden Studie sollen drei Fragen beantwortet
werden: 1. Lassen sich kortikale Generatoren des VEP unter Quadrantenstimulation
rekonstruieren, die anatomisch-funktionell plausibel sind? 2. Gibt es bei Variation der
räumlichen Frequenz eine Verlagerung des Dipols, die der retinotopen Repräsentation
des visuellen Kortex entspricht (feine Muster im Bereich der fovealen Repräsentation am
occipitalen Pol, grobe Muster entsprechend weiter innen entlang des Sulcus calcarinus)?
3. Lässt sich bei VEP analog zur fMRT die Subtraktionsmethode einsetzen?
In einem Gesichtsfeld von 20°x20° wurden stimuliert: a) die einzelnen Quadranten; sowie
für die Subtraktionsmethode b) das Gesamtfeld und c) jeweils drei Quadranten zusammen.
Für alle Bedingungen variierten wir die räumliche Frequenz in vier Schritten zwischen
0.5 und 4 cpd. Abgeleitet wurde von der gesamten Kopfhaut mit 40 Kanälen. Die
Anpassung der Dipole wurde auf der Grundlage des jeweiligen grand average mit Hilfe
von BESA (Michael Scherg, Heidelberg) vorgenommen.
Die vorläufige Auswertung von sechs Versuchspersonen zeigt: 1. Die Dipolanpassung
zur Quadrantenstimulation ergibt für die frühen Latenzen N1 und P1 die erwartete Lateralisierung.
Die N2 war hingegen für alle Reizbedingungen rechts lateralisiert. 2. Keiner
der Dipole verschiebt sich unter Variation der räumlichen Frequenz in die erwartete Richtung.
3. Bei Subtraktion der Dreiviertel-Stimulation vom Gesamtfeld lassen sich Dipole
vergleichbarer Latenz anpassen. Im Gegensatz zur Quadrantenstimulation lateralisieren
alle drei Dipole entsprechend der funktionellen Anatomie. Zusätzlich findet sich für die
P1 die erwartete Verschiebung des Dipols von innen nach außen bei Erhöhung der räumlichen
Frequenz.
Unsere Daten zeigen, dass eine plausible Dipol-Rekonstruktion bereits mit einer 40-
Kanal-Ableitung möglich ist. Darüber hinaus scheint die Subtraktionsmethode ein weiterführendes
Werkzeug in der topographischen Analyse von VEP zu sein, da sie die
erwartete retinotope Repräsentation besser abbildet als die Auswertung der direkten Quadrantenstimulation.},
web_url = {http://www.twk.tuebingen.mpg.de/twk00/},
event_name = {3. Tübinger Wahrnehmungskonferenz (TWK 2000)},
event_place = {Tübingen, Germany},
state = {published},
author = {Lehr L{lehr}, Bickford A{bickford} and Kammer T{kammer}}
}

@Poster{ 131,
title = {Maskierung visueller Reize durch Magnetstimulation},
year = {2000},
month = {2},
pages = {78},
abstract = {Transkranielle Magnetstimulation (TMS) über dem Hinterkopf kann die Wahrnehmung
visueller Reize unterdrücken. Diese Unterdrückung basiert auf einer Verschiebung der
Wahrnehmungsschwelle (Kammer & Nusseck, Neuropsychologia 36, 1998). Ziel der
vorliegenden Studie ist es, diese Modulation der Wahrnehmungsschwelle qualitativ und
quantitativ zu vergleichen mit der Maskierung des visuellen Reizes durch einen Lichtblitz.
Die Versuchspersonen mussten die Öffnungsrichtung eines kleinen U-Hakens angeben,
der 0.3° bis 0.5° parafoveal in einem unteren Gesichtsfeldquadranten mit der Dauer
eines Bildschirmtaktes geblitzt wurde (Wahlpflichtaufgabe mit 4 Alternativen). Bei zwei
verschiedenen Hintergundhelligkeiten (0.3 und 3 cd/m2) wurde die Funktion der Kontrastwahrnehmungsschwelle
mittels konstanter Stimuli ermittelt. Die parafoveale Präsentation
wurde gewählt, um eine Wahrnehmungssuppression mit einer fokalen TMS-Spule
zu erreichen. Ein Lichtblitz (15 cd/m2 bei dunklem Hintergrund, 150 cd/m2 bei hellem
Hintergrund, gesamte Monitoroberfläche für die Dauer eines Bildschirmtaktes) wurde
mit unterschiedlichen Stimulus-Onset-Asynchronien (SOA) vor oder nach der Präsentation
des U-Hakens appliziert. Vorwärts- und Rückwärtsmaskierung führte zu einer Verschiebung
der Kontrastwahrnehmungsschwelle von bis zu 8 Weberkontrasteinheiten
(WC). Fokale TMS mit einer SOA von 75 ms bis 145 ms verschob ebenso die Kontrastwahrnehmungsschwelle.
Das Maximum der Schwellenverschiebung (8 WC) wurde bei
115 ms (dunkler Hintergrund) bzw 95 ms (heller Hintergrund) erreicht. Die Ergebnisse
zeigen, dass die Schwellenverschiebung durch TMS direkt vergleichbar ist mit der
Schwellenverschiebung aufgrund einer Maskierung durch einen Lichtblitz.},
web_url = {http://www.twk.tuebingen.mpg.de/twk00/},
event_name = {3. Tübinger Wahrnehmungskonferenz (TWK 2000)},
event_place = {Tübingen, Germany},
state = {published},
author = {Puls K{puls} and Kammer T{kammer}}
}

@Poster{ 122,
title = {Zur Topographie von Phosphenen: Eine Studie mit fMRT und TMS},
year = {2000},
month = {2},
pages = {79},
abstract = {Transkranielle Magnetstimulation (TMS) über dem Hinterkopf führt zur Wahrnehmung
von konturierten Lichtblitzen, sogenannten Phosphenen. Sie erscheinen überwiegend in
den unteren Gesichtsfeldhälften, kontralateral zur Position der Spule. Unklar ist bisher, in
welchen kortikalen Strukturen die Phosphene generiert werden.
Bei bisher vier Versuchspersonen wurde die retinotope Repräsentation im visuellen Kortex
mit Hilfe der funktionellen Magnetresonanztomographie (fMRT) gemessen. Die
Exzentrizität der Retinotopie wurde durch einen langsam expandierenden flickernden
Ring abgebildet, der Polarwinkel durch ein flickerndes Segment, welches durch das
ganze Gesichtsfeld rotierte. Die Auswertung erfolgte mit dem Programm BrainVoyager
(Rainer Goebel, Maastricht). Die Ergebnisse der einzelnen Personen wurden auf der
jeweiligen individuell rekonstruierten Kortexoberfläche dargestellt und die Grenzen zwischen
den visuellen Arealen V1 bis V4 ermittelt. Die gleichen Versuchspersonen dokumentierten
die Lage und Form der Phosphene, die an verschiedenen Orten über dem
gesamten Hinterkopf durch fokale TMS evoziert wurden. Die genaue Position derTMSSpule
relativ zum Schädel der Versuchsperson wurde mit Hilfe eines stereotaktischen
Positionierungssystems mit einer Präsision von ± 1,5 mm aufgezeichnet.
Die Überlagerung der Phosphen-Stimulationsorte mit der funktionellen Architektur des
visuellen Kortex zeigt: 1. Phosphene lassen sich sowohl von oberflächlich gelegenen
Anteilen von V1 als auch von den benachbarten Arealen V2 und V3 evozieren. 2. Die
Lage der wahrgenommenen Phosphene im Gesichtsfeld folgt in erster Näherung der mit
fMRT gemessenen Retinotopie. 3. Phosphene, die durch Stimulation über V1 evoziert
werden, unterscheiden sich nicht in Größe oder Form von Phosphenen, die durch Stimulation
über V2 oder V3 evoziert werden.
Die Abhängigkeit der Lage der Phosphene von der Retinotopie des visuellen Areals
spricht gegen die Annahme von Marg & Rudiak (Optometry Vis Sci 71, 1994), daß Phosphene
durch subkortikale Stimulation der Radiatio optici generiert werden, und bestätigt
die Vermutung von Meyer et al. (Electroenceph Clin Neurophysiol Suppl 43, 1991), daß
striäre und extrastriäre Areale die Generatoren der Phosphene sind.},
web_url = {http://www.twk.tuebingen.mpg.de/twk00/},
event_name = {3. Tübinger Wahrnehmungskonferenz (TWK 2000)},
event_place = {Tübingen, Germany},
state = {published},
author = {Kammer T{kammer}, Erb M, Beck S{sbeck} and Grodd W}
}

@Poster{ 304,
title = {Zeitliche Dispersion im Sehsystem des Menschen},
year = {1999},
month = {2},
pages = {75},
abstract = {Ein Grundphänomen in der Psychophysik ist die Abhängigkeit der einfachen Reaktionszeit von der Reizstärke: sie nimmt mit abnehmender Intensität zu. Hierbei ist unklar, wo im sensomotorischen System die zeitliche Verzögerung entsteht. Denkbar ist einerseits eine intensitätsabhängige Verzögerung ausschliesslich auf der Eingangsseite. Alternativ
dazu könnte eine intensitätsabhängige, zeitkonsumierende Integration des Eingangssignals auch auf jeder Verarbeitungsstufe vom Sensor bis zur Motorik stattfinden},
web_url = {http://www.twk.tuebingen.mpg.de/twk99/},
event_name = {2. Tübinger Wahrnehmungskonferenz (TWK 99)},
event_place = {Tübingen, Germany},
state = {published},
author = {Kammer T{kammer}, Lehr L{lehr} and Kirschfeld K{kuno}}
}

@Poster{ 965,
title = {Phosphenes and transient scotomas induced by magnetic stimulation of the occipital lobe: their topographic relationship},
year = {1998},
month = {11},
volume = {24},
number = {10.6},
web_url = {http://www.sfn.org/annual-meeting/past-and-future-annual-meetings},
event_name = {28th Annual Meeting of the Society for Neuroscience (Neuroscience 1998)},
event_place = {Los Angeles, CA, USA},
state = {published},
author = {Kammer T{kammer}}
}

@Poster{ 280,
title = {Attention and metacontrast: a unifying concept},
year = {1998},
month = {2},
pages = {143},
abstract = {function of the interstimulus interval (ISI) between target and surrounding mask. We hypothesized that there might be an increase in latency of perception along with reduction
of perceived intensity.
We displayed two horizontal bars (in one line, height: 0.5 deg, width 3 deg) on a PC monitor, each for 25 ms with a variable ISI, the left one was presented first. To achieve maximal metacontrast there was no gap at the neighbored edges of the two bars.
Subjects perceive two moving lines, both start at the left and seem to ‚grow‘ to the right.
The motion seen in the right line is the well known line motion illusion, generated by cue induced visual focal attention (Steinemann et al. 1997). The motion illusion perceived in the left line is due to metacontrast. This conclusion is supported by the finding that the effect is strongest when the left line as a target is presented 40 - 80 ms before the right line acting as a mask. At equivalent time differences, metacontrast in classical paradigms
is strongest. The motion illusion results from the fact that the degree of dimming and the prolongation of latency decreases as the distance separating target from mask increases.
There is a close relationship between metacontrast and cue induced focal attention, both show, however, opposite actions: Focal attention intensifies perception of an object and reduces its latency of perception, whereas metacontrast diminishes intensity and prolongs latency.},
web_url = {http://www.twk.tuebingen.mpg.de/twk98/},
event_name = {1. Tübinger Wahrnehmungskonferenz (TWK 98)},
event_place = {Tübingen, Germany},
state = {published},
author = {Kirschfeld K{kuno} and Kammer T{kammer}}
}

@Poster{ 279,
title = {Besteht eine topographische Beziehung von Skotom und Phosphen bei Magnetstimulation desvisuellen Kortex?},
year = {1998},
month = {2},
pages = {160},
abstract = {Transkranielle Magnetstimulation (TMS) des visuellen Kortex führt bei vielen Versuchspersonen (VP) zurWahrnehmung einfacher Phosphene. Andererseits kann TMS in einem
umschriebenen Zeitfenster die visuelle Wahrnehmung unterdrücken. Bisher ist es unklar, ob die Lage der Phosphene im Sehfeld sich mit der Lage der Skotome deckt.
Das Gesichtsfeld des rechten Auges von 10 VP wurde mit einem Raster von 32 Punkten perimetriert, die einen Abstand von 1 Grad, 4 Grad und 10 Grad vom Fixationspunkt hatten.
Zusätzlich wurde der blinde Fleck mit 5 Punkten (Kontrollmessungen) bzw. 1 Punkt (TMS-Messungen) als Fixationskontrolle untersucht. Als Objekt diente ein Quadrat mit einer Seitenlänge von 0,25 Grad, welches für 1 ms auf einem Monitor mit einer Hintergrundshelligkeit
von 2,9 cd/m2 gezeigt wurde. Die Wahrnehmungsschwellen wurden nach der Strategie des Tübinger Automatik-Perimeters mit individuellen Treppenfunktionen ermittelt. Über dem Occipitalpol der VP mit einer seitlichen Abweichung von der
Mittellinie (1-2 cm) wurde TMS mit einer fokalen Doppelspule und einer Intensität von 50-75% der maximalen Ausgangsleistung appliziert. Die VP zeichneten die wahrgenommenen Phosphene auf ein Amsler-Netz. Zur Perimetrie unter TMS wurde mit einer festgewählten SOA von 70-100 ms nach jeder Präsentation ein Magnetpuls ausgelöst.
Alle 10 VP konnten Phosphene beschreiben, die sich je nach Spulenposition überwiegend in den kontralateralen unteren Quadranten parafoveal mit 1 Grad - 5 Grad ausdehnten.
Das Ausmaß der Phosphene variierte interindividuell und war in kritischer Weise abhängig von der Spulenposition. Bei 8 von 10 VP fand sich unter TMS eine Erhöhung der Wahrnehmungsschwellen von 8 - 18 dB in den Gesichtsfeldbereichen, in denen die VP das Phosphen wahrgenommen hatte. Die Winkelgröße des Skotoms stimmte bei vier VP mit der des Phosphens überein, bei einer war das Skotom kleiner und bei dreien größer.
Fokale TMS über dem visuellen Kortex führt zur Modulation der Wahrnehmungsschwellen im Sinne eines transienten Skotoms. Es besteht eine topographische Korrespondenz
zwischen den durch Magnetstimulation evozierbaren umschriebenen Phosphenen und den transienten Skotomen.},
web_url = {http://www.twk.tuebingen.mpg.de/twk98/},
event_name = {1. Tübinger Wahrnehmungskonferenz (TWK 98)},
event_place = {Tübingen, Germany},
state = {published},
author = {Kammer T{kammer} and Kirschfeld K{kuno}}
}