% % This file was created by the Typo3 extension % sevenpack version 0.7.14 % % --- Timezone: CEST % Creation date: 2013-05-24 % Creation time: 08-25-19 % --- Number of references % 19 % @Article { LogothetisEMASEBO2012, title = {Hippocampal-cortical interaction during periods of subcortical silence}, journal = {Nature}, year = {2012}, month = {11}, volume = {491}, number = {7425}, pages = {547–553}, abstract = {Hippocampal ripples, episodic high-frequency field-potential oscillations primarily occurring during sleep and calmness, have been described in mice, rats, rabbits, monkeys and humans, and so far they have been associated with retention of previously acquired awake experience. Although hippocampal ripples have been studied in detail using neurophysiological methods, the global effects of ripples on the entire brain remain elusive, primarily owing to a lack of methodologies permitting concurrent hippocampal recordings and whole-brain activity mapping. By combining electrophysiological recordings in hippocampus with ripple-triggered functional magnetic resonance imaging, here we show that most of the cerebral cortex is selectively activated during the ripples, whereas most diencephalic, midbrain and brainstem regions are strongly and consistently inhibited. Analysis of regional temporal response patterns indicates that thalamic activity suppression precedes the hippocampal population burst, which itself is temporally bounded by massive activations of association and primary cortical areas. These findings suggest that during off-line memory consolidation, synergistic thalamocortical activity may be orchestrating a privileged interaction state between hippocampus and cortex by silencing the output of subcortical centres involved in sensory processing or potentially mediating procedural learning. Such a mechanism would cause minimal interference, enabling consolidation of hippocampus-dependent memory.}, department = {Department Logothetis}, web_url = {http://www.nature.com/nature/journal/v491/n7425/full/nature11618.html}, DOI = {10.1038/nature11618}, author = {Logothetis, NK and Eschenko, O and Murayama, Y and Augath, M and Steudel, T and Evrard, HC and Besserve, M and Oeltermann, A} } @Article { 6385, title = {Coupling of neural activity and fMRI-BOLD in the motion area MT}, journal = {Magnetic Resonance in Medicine}, year = {2010}, month = {10}, volume = {28}, number = {8}, pages = {1087-1094}, abstract = {The fMRI-BOLD contrast is widely used to study the neural basis of sensory perception and cognition. This signal, however, reflects neural activity only indirectly, and the detailed mechanisms of neurovascular coupling and the neurophysiological correlates of the BOLD signal remain debated. Here we investigate the coupling of BOLD and electrophysiological signals in the motion area MT of the macaque monkey by simultaneously recording both signals. Our results demonstrate that a prominent neuronal response property of area MT, so-called motion opponency, can be used to induce dissociations of BOLD and neuronal firing. During the presentation of a stimulus optimally driving the local neurons, both field potentials [local field potentials (LFPs)] and spiking activity [multi-unit activity (MUA)] correlated with the BOLD signal. When introducing the motion opponency stimulus, however, correlations of MUA with BOLD were much reduced, and LFPs were a much better predictor of the BOLD signal than MUA. In addition, fo r a subset of recording sites we found positive BOLD and LFP responses in the presence of decreases in MUA, regardless of the stimulus used. Together, these results demonstrate that correlations between BOLD and MUA are dependent on the particular site and stimulus paradigm, and foster the notion that the fMRI-BOLD signal reflects local dendrosomatic processing and synaptic activity rather than principal neuron spiking responses.}, department = {Department Logothetis}, department2 = {Research Group Kayser}, web_url = {http://www.sciencedirect.com/science?_ob=MImg\&_imagekey=B6T9D-4YDYW8B-1-7\&_cdi=5112\&_user=29041\&_pii=S0730725X09003208\&_origin=search\&_coverDate=10\%2F31\%2F2010\&_sk=999719991\&view=c\&wchp=dGLbVtb-zSkzS\&md5=4b61d8e6911476717a27cd23535a639b\&ie=/sdarticle.pdf}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, language = {en}, DOI = {10.1016/j.mri.2009.12.028}, author = {Lippert, MT and Steudel, T and Ohl, F and Logothetis, NK and Kayser, C} } @Article { 6179, title = {Frontoparietal activity with minimal decision and control in the awake Macaque at 7T}, journal = {Magnetic Resonance Imaging}, year = {2010}, month = {10}, volume = {28}, number = {8}, pages = {1120-1128}, abstract = {Previous imaging work has identified a frontoparietal network in the human brain involved in many cognitive functions, as well as in simple updates of attended information. We examined the activation of frontoparietal areas during visual stimulation in the awake, fixating monkey, in order to determine if a similar network is present in the monkey brain and direct future electrophysiological recordings. We measured activity with BOLD fMRI in three animals and analysed the data individually for each animal, and at group level. We found reliable activations in lateral prefrontal and parietal areas, even though task-related decision making was minimal, as a response to simple update of visual information. These activations were significant for each individual animal, as well as at group level. Similar to human imaging results the update of visual input was enough to activate the frontoparietal cortex in the macaque brain, a network which is normally associated with complex cognitive control processes.}, department = {Department Logothetis}, web_url = {http://www.sciencedirect.com/science?_ob=MImg\&_imagekey=B6T9D-4Y960VY-6-C\&_cdi=5112\&_user=29041\&_pii=S0730725X09003166\&_orig=search\&_coverDate=02\%2F01\%2F2010\&_sk=999999999\&view=c\&wchp}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, language = {en}, DOI = {10.1016/j.mri.2009.12.024}, author = {Stoewer, S and Ku, S-P and Goense, J and Steudel, T and Logothetis, NK and Duncan, J and Sigala, N} } @Article { 4896, title = {A voice region in the monkey brain}, journal = {Nature Neuroscience}, year = {2008}, month = {3}, volume = {11}, number = {3}, pages = {367-374}, abstract = {For vocal animals, recognizing species-specific vocalizations is important for survival and social interactions. In humans, a voice region has been identified that is sensitive to human voices and vocalizations. As this region also strongly responds to speech, it is unclear whether it is tightly associated with linguistic processing and is thus unique to humans. Using functional magnetic resonance imaging of macaque monkeys (Old World primates, Macaca mulatta) we discovered a high-level auditory region that prefers species-specific vocalizations over other vocalizations and sounds. This region not only showed sensitivity to the \‘voice\‘ of the species, but also to the vocal identify of conspecific individuals. The monkey voice region is located on the superior-temporal plane and belongs to an anterior auditory what pathway. These results establish functional relationships with the human voice region and support the notion tha t, for different primate species, the anterior temporal regions of the brain are adapted for recognizing communication signals from conspecifics.}, url = {http://www.kyb.tuebingen.mpg.de/fileadmin/user_upload/files/publications/Petkov\%20-\%20Voice\%20Area\%20-\%20NatureNeuro\%20-\%202008_4896[0].pdf}, department = {Department Logothetis}, department2 = {Research Group Kayser}, web_url = {http://www.nature.com/neuro/journal/v11/n3/pdf/nn2043.pdf}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, language = {en}, DOI = {10.1038/nn2043}, author = {Petkov, CI and Kayser, C and Steudel, T and Whittingstall, K and Augath, M and Logothetis, NK} } @Article { 4294, title = {Functional MR imaging in the awake monkey: effects of motion on dynamic off-resonance and processing strategies}, journal = {Magnetic Resonance Imaging}, year = {2007}, month = {7}, volume = {25}, number = {6}, pages = {869-882}, department = {Department Logothetis}, web_url = {http://www.sciencedirect.com/science?_ob=MImg\&_imagekey=B6T9D-4NJP3PF-8-1\&_cdi=5112\&_user=29041\&_orig=browse\&_coverDate=07\%2F31\%2F2007\&_sk=999749993\&view=c\&wchp=dGLbVzW-zSkzS\&md5=65c3bcf3da054d8435af25a5cff90ab8\&ie=/sdarticle.pdf}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, language = {en}, DOI = {10.1016/j.mri.2007.03.002}, author = {Pfeuffer, J and Shmuel, A and Keliris, GA and Steudel, T and Merkle, H and Logothetis, NK} } @Article { 4433, title = {Robust Controlled Functional MRI in Alert Monkeys at High Magnetic Field: Effects of Jaw and Body Movements}, journal = {NeuroImage}, year = {2007}, month = {7}, volume = {36}, number = {3}, pages = {550-570}, department = {Department Logothetis}, web_url = {http://www.sciencedirect.com/science?_ob=MImg\&_imagekey=B6WNP-4NFXDGH-1-1G\&_cdi=6968\&_user=29041\&_orig=browse\&_coverDate=07\%2F01\%2F2007\&_sk=999639996\&view=c\&wchp=dGLzVlz-zSkWb\&md5=54c45acb296ee126362acb0f149797d8\&ie}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, language = {en}, DOI = {10.1016/j.neuroimage.2007.02.057}, author = {Keliris, GA and Shmuel, A and Ku, S-P and Pfeuffer, J and Oeltermann, A and Steudel, T and Logothetis, NK} } @Article { 2894, title = {Anatomical and Functional MR Imaging in the Macaque Monkey Using a Vertical Large-bore 7 Tesla Setup}, journal = {Magnetic Resonance Imaging}, year = {2004}, month = {12}, volume = {22}, number = {10}, pages = {1343-1359}, url = {http://www.kyb.tuebingen.mpg.de/fileadmin/user_upload/files/publications/pdf2894.pdf}, department = {Department Logothetis}, web_url = {http://www.sciencedirect.com/science?_ob=MImg\&_imagekey=B6T9D-4FF9547-2-K\&_cdi=5112\&_user=29041\&_orig=search\&_coverDate=12\%2F31\%2F2004\&_sk=999779989\&view=c\&wchp=dGLzVlz-zSkzk\&md5=26f8916c8f8a658f9009cce48bfcedfc\&ie=/sdarticle.pdf}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, language = {en}, DOI = {10.1016/j.mri.2004.10.004}, author = {Pfeuffer, J and Merkle, H and Beyerlein, M and Steudel, T and Logothetis, NK} } @Inproceedings { 2529, title = {Perfusion-based high-resolution fMRI in the primate brain using a novel vertical large-bore 7 Tesla setup}, journal = {ISMRM Workshop on Quantitative Cerebral Perfusion Imaging Using MRI: A Technical Perspective, Proc ISMRM, Venice}, year = {2004}, month = {3}, pages = {108-109}, abstract = {Functional MR imaging in monkeys promises a bridge between brain research in humans and the large body of systems neuroscience work in animals. Prerequisite for successful interspecies-comparisons, however, is a profound understanding of the neural events underlying the hemodynamic responses. Combined physiology and neuroimaging experiments made the first step in this direction by examining directly the relationship of cell activity to the BOLD signal [1]. The tight coupling between regional neural activity and blood flow, however, suggests that perfusion-based MRI may improve even further the electrophysiological investigations of the neurovascular coupling, as perfusion imaging measures cerebral blood flow (CBF) directly at the capillary level. Moreover, CBF changes and interleaved-acquired BOLD data can be combined to compute changes in oxygen consumption rate. Obtaining functional CBF maps with high spatial resolution is challenging, because the CBF signal is intrinsically low and the signal-to-noise ratio is critical. Here we report the first high-resolution CBF maps that were obtained with voxel sizes as small as 0.5 x 0.5 x 3 mm3 in the Macaca mulatta. High sensitivity was achieved by using a high magnetic field scanner and custom-made RF combination-coil designs. CBF maps and functional CBF data were acquired and compared with BOLD data in the macaque primary visual cortex.}, url = {http://www.kyb.tuebingen.mpg.de/fileadmin/user_upload/files/publications/pdf2529.pdf}, department = {Department Logothetis}, web_url = {http://www.ismrm.org/workshops/Perfusion_Imaging/}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {Kyoto, Japan}, event_name = {ISMRM Workshop on Quantitative Cerebral Perfusion Imaging Using MRI: A Technical Perspective}, author = {Pfeuffer, J and Steudel, T and Merkle, H and Logothetis, NK} } @Poster { 4586, title = {A voice-area in the primate brain: Enhanced representation of the ''voice'' of conspecifics}, year = {2007}, month = {9}, abstract = {The human voice not only transmits spoken language, but itself carries considerable meaning. Reflecting this importance, imaging studies have identified a region in the auditory cortex of the human brain that is sensitive to the human voice. For animals that cannot expand their vocal repertoire linguistically, the correct interpretation of the vocalizations of their conspecifics is of even greater importance for survival and social interactions. However, it is uncertain whether other primates share homologous voice regions or whether the human voice area is tightly linked to human language and thus unique. Here, we used high-resolution functional imaging (fMRI) of macaque monkeys to compare the strength of the activity response to conspecific vocalizations with that elicited by other sound categories, including the vocalizations of heterospecifics. We found several brain regions demonstrating a strong preference for conspecific vocalizations and identified a candidate ‘voice’ area located in the higher proc essing stages of auditory cortex, in the anterior portions of the superior-temporal plane (STP). In contrast, the corresponding well-known human voice area resides below the STP, highlighting the possibility of an evolutionary expansion and differentiation of the human auditory cortex away from the STP. The presence of a voice region in nonhuman primates supports the notion that such specialized areas do not depend on linguistic capabilities. In all cases, our findings suggest that the auditory cortex of other vocal animals possess regions that are specialized for processing the ‘voice‘ of conspecifics.}, department = {Department Logothetis}, web_url = {http://www.dzg-ev.de/de/veranstaltungen/externe/eec2007.php}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {Hannover, Germany}, event_name = {International Symposium on Evolution of Emotional Communication (EEC 2007)}, language = {en}, author = {Petkov, CI and Kayser, C and Whittingstall, K and Steudel, T and Augath, M and Logothetis, NK} } @Poster { 4125, title = {Functional imaging of organization and specialization in the monkey auditory cortex}, journal = {Hearing Research}, year = {2007}, month = {7}, volume = {229}, number = {1-2}, pages = {239-240}, abstract = {We localized many fields in the auditory cortex of the macaque monkey and studied which auditory regions are specialized for processing the communication sounds of the species. First, we used high resolution fMRI at 4.7 and 7 T to functionally map the auditory cortex of behaving and of anesthetized monkeys. The identified fields included regions already well described by anatomical and neurophysiological techniques as well as those whose anatomical parcellation remained without functional support. To localize fields, we varied the frequencies of tonal or bandpassed-noise sounds, and obtained spatially specific activity patterns throughout much of auditory cortex. We then statistically tested the frequency-selective gradients within these regions of auditory cortex and the results suggest that 11 fields contain neurons tuned for the frequency of sounds. The obtained maps provide functional support for a model according to which three fields in primary auditory cortex (the auditory ‘core’) are surrounded by eight neighboring ‘belt’ fields in non-primary auditory cortex. Following this non-invasive mapping, we examined which of the localized fields, if any, were specialized for processing the communication sounds of these species in relation to other sounds. Natural sounds were presented as stimulation, including the vocalizations of conspecifics, of other animals, and other natural sounds. Control stimuli were also used. The vocalizations of conspecifics generally elicited greater responses throughout auditory cortex than did the other sounds. The strongest specificity for these vocalizations seemed to be in the anterior fields of auditory cortex, but also extended anteriorly outside of the auditory core and belt fields that were localized with tone and noise stimuli. The data suggest a specialization for the processing of species-specific vocalizations in the anterior portions of auditory cortex, including the poorly understood fields of the auditory parabelt. These fMRI data reflect ethological influences on brain organization and can help us to delineate neural networks in the nonhuman primate that are expected to have an evolutionary relationship to speech processing areas in the human brain.}, department = {Department Logothetis}, web_url = {http://www.sciencedirect.com/science/article/pii/S0378595506003108}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {Grantham, UK}, event_name = {International Conference on the Auditory Cortex 2006: The Listening Brain}, DOI = {10.1016/j.heares.2006.11.003}, author = {Petkov, CI and Kayser, C and Augath, M and Steudel, T and Logothetis, NK} } @Poster { 4123, title = {Functional imaging of organization and specialization in the monkey auditory cortex}, year = {2006}, month = {10}, volume = {36}, number = {344.9}, abstract = {We localized numerous fields in the auditory cortex of the macaque monkey and studied which regions are specialized for processing the communication sounds of the species. First, we used high resolution fMRI at 4.7 and 7 Tesla to functionally map the auditory cortex of behaving and of anesthetized monkeys. The identified fields included regions already well described by anatomical and neurophysiological techniques as well as those whose anatomical parcellation remained without functional support. To localize fields, we varied the frequency content of tonal or band-passed-noise sounds, and obtained spatially specific activity patterns throughout much of auditory cortex. We then statistically tested the frequency-selective gradients within these regions of auditory cortex and the results suggest that 11 fields contain neurons tuned for the frequency of sounds. The obtained maps provide functional support for a model according to which three fields in primary auditory cortex (the auditory ‘core’) are surrounded by eight neighboring ‘belt’ fields in non-primary auditory cortex. Following this non-invasive mapping, we examined which of the localized fields, if any, were specialized for processing the communication sounds of these species in relation to other sounds. Natural sounds were presented as stimulation, including the vocalizations of conspecifics, of other animals, and other natural sounds. Control stimuli were also used. The vocalizations of conspecifics generally elicited greater responses throughout auditory cortex than did the other sounds. The strongest specificity for these vocalizations seemed to be in the anterior fields of auditory cortex, but also extended anteriorly outside of the auditory core and belt fields that were localized with tone and noise stimuli. The data suggest a specialization for the processing of species-specific vocalizations in the anterior portions of auditory cortex, including the poorly understood fields of the auditory parabelt. These fMRI data reflect ethological influences on brain organization and can help us to delineate neural networks in the nonhuman primate that are expected to have an evolutionary relationship to speech processing areas in the human brain.}, url = {http://www.kyb.tuebingen.mpg.de/fileadmin/user_upload/files/publications/Petkov_et_al_SFN\%20Abstract\%2006_final_4123[0].pdf}, department = {Department Logothetis}, web_url = {http://www.sfn.org/index.aspx?pagename=abstracts_ampublications}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {Atlanta, GA, USA}, event_name = {36th Annual Meeting of the Society for Neuroscience (Neuroscience 2006)}, author = {Petkov, C and Kayser, C and Augath, M and Steudel, T and Logothetis, NK} } @Poster { ShmuelSOL2006, title = {Neuronal correlates of fMRI signal response in alert monkey V1}, year = {2006}, month = {10}, volume = {36}, number = {545.14}, abstract = {The majority of functional brain imaging studies rely on task induced hemodynamic responses to infer the underlying changes in neuronal activity. Characterizing the relationship between hemodynamic responses and locally measured neuronal activity is crucial for correct interpretation of functional MRI data. Most previous studies on this relationship have used anesthetized preparations with possible confounding effects of anesthesia. This study is aimed at characterizing the local neuronal correlates of Blood Oxygenation Level Dependent response to short presentation of visual stimuli in alert fixating monkey visual area V1. Monkeys were trained to stay still throughout trials lasting 20 s, within which they fixated for 6 s and were presented with a stimulus for 4 s. Gradient Echo and Spin Echo functional MRI was performed using a 7 T vertical bore magnet and a surface RF coil positioned around a recording chamber (2 segments, TE 19 and 40 ms for Gradient Echo and Spin Echo respectively, resolution 1\(\times\)1\(\times\)2 mm, acquisition time 1 s / volume). Interleaved between functional MRI scans, electrophysiological signals were recorded using identical paradigms. The BOLD signal was sampled from a region of interest (6\(\times\)6\(\times\)2 mm) around the electrode in V1. Data will be shown on the coupling of different bands of the neuronal signal to the BOLD response, and on the relationship between the locally measured visual evoked response and BOLD response.}, department = {Department Logothetis}, web_url = {http://www.sfn.org/index.aspx?pagename=abstracts_ampublications}, event_place = {Atlanta, GA, USA}, event_name = {36th Annual Meeting of the Society for Neuroscience (Neuroscience 2006)}, author = {Shmuel, A and Steudel, T and Oeltermann, A and Logothetis, NK} } @Poster { 4126, title = {Organization and specialization of the monkey auditory cortex revealed with MR imaging}, year = {2006}, month = {10}, number = {28}, department = {Department Logothetis}, web_url = {http://www.apan.jhu.edu/Program_APANIV.htm}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {Atlanta, GA, USA}, event_name = {Tucker-Davis Symposium on Advances and Perspectives in Auditory Neurophysiology (APAN IV)}, author = {Petkov, C and Kayser, C and Augath, M and Steudel, T and Logothetis, N} } @Poster { 3539, title = {fMRI of Macaque Auditory Cortex in Awake and in Anesthetized Animals}, year = {2005}, month = {11}, volume = {35}, number = {851.5}, abstract = {Functional magnetic resonance imaging (fMRI) with non-human primates is invaluable because localized patterns of activity can guide subsequent neurophysiological recordings. However, it is unknown whether fMRI of the macaque monkey can reveal reliable auditory activations consistent with known properties of primate auditory cortical fields (ACFs). We used high-field (4.7- and 7-Tesla) fMRI to image the blood-oxygen level dependent response (BOLD) of auditory cortex in awake and in anesthetized macaques. For awake-animal imaging we trained a macaque to complete long duration trials of visual fixation in combination with minimal body movement. Scanning this animal at 7T during sound presentation revealed robust activity over auditory cortex in the superior temporal plane. A paradigm where stimulation alternated with image acquisition revealed greater auditory activity than continuous imaging where sound stimulation must compete with the scanner noise. Imaging data with more extensive sound stimulation was obtained from anesthetized animals since these experiments allow for quicker data acquisition. Here, we used sounds varying in center frequency and bandwidth as have neurophysiological experiments mapping the basic organizational properties of macaque ACFs. In the antero-posterior direction, regions within the lateral sulcus were selective for sounds with low and high center frequencies, revealing expected frequency selective gradients (tonotopy) with multiple mirror reversals of these gradients. In comparison to tonal stimulation, sounds with greater spectral bandwidth activated more lateral and medial portions of the superior temporal plane, consistent with this activity occurring over non-primary ACFs. In summary, high-field fMRI reveals the global organization of macaque auditory cortex and will be important for helping us to understand how the primate auditory cortex is functionally organized.}, department = {Department Logothetis}, web_url = {http://www.sfn.org/absarchive/}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {Washington, DC, USA}, event_name = {35th Annual Meeting of the Society for Neuroscience (Neuroscience 2005)}, language = {en}, author = {Petkov, CI and Kayser, C and Augath, M and Steudel, T and Logothetis, NK} } @Poster { ShmuelDSL2005, title = {Increased activity in monkey V1 and V2 during fixation}, year = {2005}, month = {11}, volume = {35}, number = {165.9}, abstract = {Functional brain imaging and physiology studies of the visual cortex often utilize fixation on a spot as their baseline condition. It is not clear, however, whether fixation per se causes changes in activity in early retinotopic visual areas. To investigate possible changes in activity in V1 and V2 during fixation, we conducted fMRI experiments in alert monkeys. Monkeys were trained to stay still for 20 s long trials. Each trial began with 3 s in which a blank dark image was presented, followed by the presentation of a fixation spot (0.15 degrees radius) for 7 s. The animals fixated within 1 degree from the spot. A blank dark image was presented during the last 10 s of each trial. A surface coil (40 mm diameter) was positioned in proximity to the lateral part of the operculum. fMRI was conducted in a 7T vertical bore Bruker magnet, using a GE-EPI sequence. Cross-correlation analysis revealed increased activity in response to fixation, in the central visual field representation of V1 and V2 (eccentricities 0 to 2 degrees). To verify this response using a model-free analysis, a rotating checkers pattern bound between eccentricities of 0 and 1 degree was used as a localizer stimulus. In response to the localizer stimulus, increased activity (2.5\%) was observed in the foveal representation of V1 and V2. The map obtained using the localizer was used as a region of interest to sample the time-course during trials in which only the fixation spot was presented. An increased activity was detected in these trials in V2 (\verb=~=1\%) and in V1 (\verb=~=0.5\%). To check whether this increased activity could be caused by the small fixation spot, we varied the luminance of the fixation spot and its contrast relative to the dark background. The amplitude of the response was largely invariant to differences in the contrast of the fixation point relative to the background, whether it was 90\%, 50\%, or 10\%. These findings indicate the involvement of attentional mechanisms in early visual cortex during fixation.}, department = {Department Logothetis}, web_url = {http://www.sfn.org/absarchive/}, event_place = {Washington, DC, USA}, event_name = {35th Annual Meeting of the Society for Neuroscience (Neuroscience 2005)}, author = {Shmuel, A and Deubelius, A and Steudel, T and Logothetis, NK} } @Poster { DeubeliusSLS2005, title = {Negative BOLD response in early visual areas of the alert monkey}, year = {2005}, month = {11}, volume = {35}, number = {189.10}, abstract = {Previous studies demonstrated negative BOLD response beyond the stimulated regions in V1, V2 and V3 in humans and anesthetized monkeys. Here we demonstrate negative BOLD response in alert monkey early visual areas. Monkeys were trained to stay still during 20 s long trials. Each trial began with 3 s in which a blank gray image was presented, followed by the presentation of a fixation spot (0.15 degrees radius) for 3 s, and a stimulus for 4 s. The stimulus consisted of rotating checkers pattern bound between eccentricities of 2 and 4 degrees. The animals fixated within 1 degree from the fixation spot. A blank gray image was presented during the last 10 s of each trial. A surface coil (40 mm diameter) was positioned in proximity to the operculum of one hemisphere. fMRI was conducted in a vertical bore Bruker 7T magnet, using a GE-EPI sequence. Increased activity (2.5\%) was observed within the V1, V2, and V3 representations of the stimulated regions in the visual space. Negative BOLD response was detected in these areas in regions corresponding to more peripheral eccentricities. We are currently conducting experiments to further characterize this negative BOLD response.}, department = {Department Logothetis}, web_url = {http://www.sfn.org/absarchive/}, event_place = {Washington, DC, USA}, event_name = {35th Annual Meeting of the Society for Neuroscience (Neuroscience 2005)}, author = {Deubelius, A and Steudel, T and Logotethis, NK and Shmuel, A} } @Poster { 2530, title = {Perfusion-based high-resolution fMRI in the primate brain using a novel vertical large-bore 7 Tesla setup}, journal = {NeuroImage}, year = {2004}, month = {6}, volume = {22}, number = {Supplement 1}, pages = {e2424-e2426}, abstract = {Functional MR imaging in monkeys promises to build a bridge between brain research in humans and the large body of systems neuroscience work in animals. Simultaneous fMRI and electrophysiology was recently used in the anesthetized monkey to elucidate the neural activity underlying the fMRI BOLD signal [1]. Perfusion-based MRI measures cerebral blood flow (CBF) at the capillary level and can be used for functional studies based on the tight spatial coupling between brain activity and blood flow. From CBF changes and interleaved-acquired BOLD data, changes in oxygen consumption can be calculated. Obtaining functional CBF maps with high spatial resolution is a major challenge, because the CBF signal is intrinsically low and the signal-to-noise ratio is critical. In this study, high-resolution CBF maps were obtained with voxel sizes as small as 0.5 x 0.5 x 3 mm3 in the Macaca mulatta for the first time. High sensitivity was made possible by signal-to-noise gains at the high magnetic field of 7 Tesla and by using a customized RF combination coil design. In first experiments, CBF maps and functional CBF data were acquired and compared with functional BOLD data in the primary visual cortex. For CBF, large contrast-to-noise gains were obtained at high spatial resolution similar as previously reported in humans [2]. These first results demonstrate that the sensitivity gains at high field can be used to study CBF changes in primate brain with spatial dimensions well below the cortical thickness. This is significant for the understanding of localized brain function and the physiological basis of functional neuroimaging.}, url = {http://www.kyb.tuebingen.mpg.de/fileadmin/user_upload/files/publications/pdf2530.pdf}, department = {Department Logothetis}, web_url = {http://www.sciencedirect.com/science/article/pii/S1053811905700203}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {Budapest, Hungary}, event_name = {10th Annual Meeting of the Organization for Human Brain Mapping (HBM 2004)}, DOI = {10.1016/S1053-8119(05)70020-3}, author = {Pfeuffer, J and Steudel, T and Merkle, H and Logothetis, NK} } @Poster { 2038, title = {Functional MR imaging of the awake monkey in a novel vertical large-bore 7 Tesla setup}, year = {2003}, month = {7}, volume = {11}, number = {1781}, pages = {349}, abstract = {First fMRI results in the awake trained monkey (Macaca mulatta) using a novel vertical 7T/60cm MR system are reported. The setup was custom-designed for MR imaging of monkeys in upright position and simultaneous electrophysiological recording. Using fast gradients and optimized RF coils, the benefits of high magnetic field with increased signal and contrast-to-noise ratio are demonstrated in high-resolution anatomical and functional images.}, url = {http://www.kyb.tuebingen.mpg.de/fileadmin/user_upload/files/publications/pdf2038.pdf}, department = {Department Logothetis}, web_url = {http://www.ismrm.org/03/}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {Toronto, Canada}, event_name = {11th Scientific Meeting of the International Society of Magnetic Resonance in Medicine (ISMRM 2003)}, author = {Pfeuffer, J and Pauls, J and Augath, MA and Steudel, T and Merkle, H and Logothetis, NK} } @Conference { LogothetisSMASO2006, title = {Microstimulation and fMRI in anesthetized and alert monkeys: Conditions for transsynaptic BOLD activation}, year = {2006}, month = {10}, volume = {36}, number = {114.10}, abstract = {We have recently combined electrical stimulation and fMRI and demonstrated that the excitability properties of the directly stimulated elements in neocortex using this method are very similar to those obtained with either intracortical recordings or behavioral methods (Tolias et al., 2005). Microstimulation in cortical area V1 of the macaque activated mainly the pyramidal fibers, and the effective current spread, that was measured by means of the BOLD activation, was found to be greater than that obtained with the other two methods. Stimulation of V1 (and in later studies of MT), however, revealed mainly the monosynaptic targets of each stimulated region. Here we set out to elucidate the conditions for which transsynaptic effects can be obtained. Experiments were conducted in anesthetized and alert monkeys in a 4.7T/40cm and 7T/60 scanner, respectively. Electrical stimulation was delivered using a biphasic pulse generator attached to a constant-current stimulus isolation unit. Constant-current charge-balanced, band-limited pulses of different center frequency, pulse duration and current strength were delivered to the brain for periods of 4 sec preceded and followed by 4 sec and 12 sec blank periods, respectively. The compensation circuit, designed to minimize interference generated by the switching gradients during recording, was always active, alleviating all gradient-induced currents in the range of the stimulation current. Local microstimulation was applied in dLGN, pulvinar, striate and extrastriate cortex. The areas activated upon stimulation of each of these sites was found to depend primarily on the central frequency of the frequency band used. Transsynaptic activation also depended on stimulation condition. Differences between the anesthetized and alert monkey experiments will be discussed.}, department = {Department Logothetis}, talk_type = {Abstract Talk}, web_url = {http://www.sfn.org/index.aspx?pagename=abstracts_ampublications}, event_place = {Atlanta, GA, USA}, event_name = {36th Annual Meeting of the Society for Neuroscience (Neuroscience 2006)}, author = {Logothetis, NK and Sultan, F and Murayama, Y and Augath, M and Steudel, T and Oeltermann, A} }