@Article{ KapoorKKLP2013,
title = {Development of Tube Tetrodes and a Multi-Tetrode Drive for deep structure electrophysiological recordings in the macaque brain},
journal = {Journal of Neuroscience Methods},
year = {2013},
month = {5},
volume = {216},
number = {1},
pages = {43–48},
abstract = {Understanding the principles that underlie information processing by neuronal networks requires simultaneous recordings from large populations of well isolated single units. Twisted wire tetrodes (TWTs), typically made by winding together four ultrathin wires (diameter–12 to 25 microns), are ideally suited for such population recordings. They are advantageous over single electrodes; both with respect to quality of isolation as well as the number of single units isolated and have therefore been used extensively for superficial cortical recordings. However, their limited tensile strength poses a difficulty to their use for recordings in deep brain areas. We therefore developed a method to overcome this limitation and utilize tetrodes for electrophysiological recordings in the inferotemporal cortex of rhesus macaque. We fabricated a novel, stiff tetrode called the tube tetrode (TuTe) and developed a multi-tetrode driving system for advancing up to 5 TuTes through a ball and socket chamber to precise locations in the temporal lobe of a rhesus macaque. The signal quality acquired with TuTes was comparable to conventional TWTs and allowed excellent isolation of multiple single units. We describe here a simple method for constructing TuTes, which requires only standard laboratory equipment. Further, our TuTes can be easily adapted to work with other microdrives commonly used for electrophysiological investigation in the macaque brain and produce minimal damage to the cortex along its path because of their ultrathin diameter. The tetrode development described here could allow studying neuronal populations in deep lying brain structures previously difficult to reach with the current technology.},
web_url = {http://www.sciencedirect.com/science/article/pii/S0165027013001222},
state = {published},
DOI = {10.1016/j.jneumeth.2013.03.017},
author = {Kapoor V{vishal}{Department Physiology of Cognitive Processes}, Krampe E{krampe}{Department Physiology of Cognitive Processes}, Klug A{klug}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Panagiotaropoulos TI{theofanis}{Department Physiology of Cognitive Processes}}
}

@Article{ PanagiotaropoulosKLD2013,
title = {A Common Neurodynamical Mechanism Could Mediate Externally Induced and Intrinsically Generated Transitions in Visual Awareness},
journal = {PLoS ONE},
year = {2013},
month = {1},
volume = {8},
number = {1},
pages = {1-10},
abstract = {The neural correlates of conscious visual perception are commonly studied in paradigms of perceptual multistability that allow multiple perceptual interpretations during unchanged sensory stimulation. What is the source of this multistability in the content of perception? From a theoretical perspective, a fine balance between deterministic and stochastic forces has been suggested to underlie the spontaneous, intrinsically driven perceptual transitions observed during multistable perception. Deterministic forces are represented by adaptation of feature-selective neuronal populations encoding the competing percepts while stochastic forces are modeled as noise-driven processes. Here, we used a unified neuronal competition model to study the dynamics of adaptation and noise processes in binocular flash suppression (BFS), a form of externally induced perceptual suppression, and compare it with the dynamics of intrinsically driven alternations in binocular rivalry (BR). For the first time, we use electrophysiological, biologically relevant data to constrain a model of perceptual rivalry. Specifically, we show that the mean population discharge pattern of a perceptually modulated neuronal population detected in electrophysiological recordings in the lateral prefrontal cortex (LPFC) during BFS, constrains the dynamical range of externally induced perceptual transitions to a region around the bifurcation separating a noise-driven attractor regime from an adaptation-driven oscillatory regime. Most interestingly, the dynamical range of intrinsically driven perceptual transitions during BR is located in the noise-driven attractor regime, where it overlaps with BFS. Our results suggest that the neurodynamical mechanisms of externally induced and spontaneously generated perceptual alternations overlap in a narrow, noise-driven region just before a bifurcation where the system becomes adaptation-driven.},
web_url = {http://www.plosone.org/article/fetchObjectAttachment.action;jsessionid=EF29256D0A77BD57133469DBE40B96AA?uri=info%3Adoi%2F10.1371%2Fjournal.pone.0053833&representation=PDF},
state = {published},
DOI = {10.1371/journal.pone.0053833},
EPUB = {e53833},
author = {Panagiotaropoulos TI{theofanis}{Department Physiology of Cognitive Processes}, Kapoor V{vishal}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Deco G}
}

@Article{ MaierPTK2012,
title = {Introduction to research topic – binocular rivalry: a gateway to studying consciousness},
journal = {Frontiers in Human Neuroscience},
year = {2012},
month = {9},
volume = {6},
number = {263},
pages = {1-3},
abstract = {In 1593, Neapolitan polymath Giambattista della Porta publicly lamented that he was unable to improve his impressive productivity (he had published in areas as diverse as cryptography, hydraulics, pharmacology, optics, and classic fiction). Della Porta was trying to read two books simultaneously by placing both volumes side-by-side, and using each eye independently. To his great surprise, his setup allowed him to only read one book at a time. This discovery arguably marks the first written account of binocular rivalry (Wade, 2000) – a perceptual phenomenon that more than 400 years later still both serves to intrigue as well as to illuminate the limits of scientific knowledge. At first glance, binocular rivalry is an oddball. In every day vision, our eyes receive largely matching views of the world. The brain combines the two images into a cohesive scene, and concurrently, perception is stable. However, when showing two very different images (such as two different books) to each eye, the brain resolves the conflict by adopting a “diplomatic” strategy. Rather than mixing the views of the two eyes into an insensible visual percept, observers perceive a dynamically changing series of perceptual snapshots, with one eye’s view dominating for a few seconds before being replaced by its rival from the other eye. With prolonged viewing of a rivalrous stimulus, one inevitably experiences a sequence of subjective perceptual reversals, separated by random time intervals, and this process continues for as long as the sensory conflict is present.},
web_url = {http://www.frontiersin.org/Human_Neuroscience/10.3389/fnhum.2012.00263/full},
state = {published},
DOI = {10.3389/fnhum.2012.00263},
author = {Maier A{amaier}{Department Physiology of Cognitive Processes}, Panagiotaropoulos TI{theofanis}{Department Physiology of Cognitive Processes}, Tsuchiya N and Keliris GA{george}{Department Physiology of Cognitive Processes}}
}

@Article{ PanagiotaropoulosDKL2012,
title = {Neuronal Discharges and Gamma Oscillations Explicitly Reflect Visual Consciousness in the Lateral Prefrontal Cortex},
journal = {Neuron},
year = {2012},
month = {6},
volume = {74},
number = {5},
pages = {924–935},
abstract = {Neuronal discharges in the primate temporal lobe, but not in the striate and extrastriate cortex, reliably reflect stimulus awareness. However, it is not clear whether visual consciousness should be uniquely localized in the temporal association cortex. Here we used binocular flash suppression to investigate whether visual awareness is also explicitly reflected in feature-selective neural activity of the macaque lateral prefrontal cortex (LPFC), a cortical area reciprocally connected to the temporal lobe. We show that neuronal discharges in the majority of single units and recording sites in the LPFC follow the phenomenal perception of a preferred stimulus. Furthermore, visual awareness is reliably reflected in the power modulation of high-frequency (>50 Hz) local field potentials in sites where spiking activity is found to be perceptually modulated. Our results suggest that the activity of neuronal populations in at least two association cortical areas represents the content of conscious visual perception.},
web_url = {http://www.sciencedirect.com/science/article/pii/S0896627312003807},
state = {published},
DOI = {10.1016/j.neuron.2012.04.013},
author = {Panagiotaropoulos TI{theofanis}{Department Physiology of Cognitive Processes}, Deco G, Kapoor V{vishal}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ TheodoniPKLD2011,
title = {Cortical microcircuit dynamics mediating binocular rivalry: the role of adaptation in inhibition},
journal = {Frontiers in Human Neuroscience},
year = {2011},
month = {11},
volume = {5},
number = {145},
pages = {1-19},
abstract = {Perceptual bistability arises when two conflicting interpretations of an ambiguous stimulus or images in binocular rivalry (BR) compete for perceptual dominance. From a computational point of view, competition models based on cross-inhibition and adaptation have shown that noise is a crucial force for rivalry, and operates in balance with adaptation. In particular, noise-driven transitions and adaptation-driven oscillations define two dynamical regimes and the system explains the observed alternations in perception when it operates near their boundary. In order to gain insights into the microcircuit dynamics mediating spontaneous perceptual alternations, we used a reduced recurrent attractor-based biophysically realistic spiking network, well known for working memory, attention, and decision making, where a spike-frequency adaptation mechanism is implemented to account for perceptual bistability. We thus derived a consistently reduced four-variable population rate model using mean-field techniques, and we tested it on BR data collected from human subjects. Our model accounts for experimental data parameters such as mean time dominance, coefficient of variation, and gamma distribution fit. In addition, we show that our model operates near the bifurcation that separates the noise-driven transitions regime from the adaptation-driven oscillations regime, and agrees with Levelt’s second revised and fourth propositions. These results demonstrate for the first time that a consistent reduction of a biophysically realistic spiking network of leaky integrate-and-fire neurons with spike-frequency adaptation could account for BR. Moreover, we demonstrate that BR can be explained only through the dynamics of competing neuronal pools, without taking into account the adaptation of inhibitory interneurons. However, the adaptation of interneurons affects the optimal parametric space of the system by decreasing the overall adaptation necessary for the bifurcation to occur, and introduces oscillations in the spontaneous state.},
web_url = {http://www.frontiersin.org/Journal/DownloadFile.ashx?pdf=1&FileId=%2052745&articleId=%2014281&Version=%201&ContentTypeId=21&FileName=%20fnhum-05-00145.pdf},
state = {published},
DOI = {10.3389/fnhum.2011.00145},
author = {Theodoni P, Panagiotaropoulos TI{theofanis}{Department Physiology of Cognitive Processes}, Kapoor V{vishal}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Deco G}
}

@Article{ DiamantopoulouSPS2011,
title = {Reward or its denial during the neonatal period affects adult spatial memory and hippocampal phosphorylated cAMP response element-binding protein levels of both the neonatal and adult rat},
journal = {Neuroscience},
year = {2011},
month = {5},
volume = {181},
pages = {89-99},
abstract = {Early life experiences, particularly mother–infant interactions, have been shown to influence adult coping and learning abilities via gene-environment interactions. We have developed a paradigm, in which mother contact is used as either a positive or a negative reinforcer in a T-maze, during postnatal days 10–13. In both neonates receiving (RER) or denied (DER) the expected reward, exposure to the memory test in the absence of the mother resulted in a remarkable increase in the number of pCREB immunopositive cells, when compared to their corresponding levels 2 h after the completion of the training process, but also to the levels of naïve animals. In the CA3 area, the pattern of pCREB immunoreactivity, when evaluated 2 h after the completion of the training on postnatal day 13 seemed to distinguish between the two different neonatal experiences in the T-maze, with the DER pups showing higher levels of pCREB immunopositive cells than the RER. Exposure to the Morris Water Maze (MWM) during adulthood revealed a memory advantage of the DER animals compared to the RER and the animals not exposed to the neonatal experience. Relevantly, in the DER animals an increased number of pCREB immunopositive cells was observed in the CA3 area even 24 h after the end of MWM training. When also measured after exposure to the probe trial, the number of pCREB immunopositive cells was again higher in the DER compared to the RER animals. In conclusion, we show that a learning experience involving discrepancy during the particularly plastic neonatal period is able to induce long-term effects, which result in enhanced adult hippocampal dependent spatial memory. Furthermore, our data document a role of plasticity molecules like pCREB in mediating hippocampal dependent learning and detection of novelty not only in adulthood, but also more importantly in the neonatal period of the rat.},
web_url = {http://www.sciencedirect.com/science?_ob=MiamiImageURL&_cid=271071&_user=29041&_pii=S0306452211002338&_check=y&_origin=&_coverDate=05-May-2011&view=c&wchp=dGLbVBA-zSkzk&md5=fc343ec1227e95e720dbc91df8cacb14/1-s2.0-S0306452211002338-main.pdf},
state = {published},
DOI = {10.1016/j.neuroscience.2011.03.002},
author = {Diamantopoulou A, Stamatakis A, Panagiotaropoulos T{theofanis} and Stylianopoulou F}
}

@Article{ 6058,
title = {Visually Driven Activation in Macaque Areas V2 and V3 without Input from the Primary Visual Cortex},
journal = {PLoS ONE},
year = {2009},
month = {5},
volume = {4},
number = {5},
pages = {1-14},
abstract = {Creating focal lesions in primary visual cortex (V1) provides an opportunity to study the role of extra-geniculo-striate pathways for activating extrastriate visual cortex. Previous studies have shown that more than 95% of neurons in macaque area V2 and V3 stop firing after reversibly cooling V1 [1], [2], [3]. However, no studies on long term recovery in areas V2, V3 following permanent V1 lesions have been reported in the macaque. Here we use macaque fMRI to study area V2, V3 activity patterns from 1 to 22 months after lesioning area V1. We find that visually driven BOLD responses persist inside the V1-lesion projection zones (LPZ) of areas V2 and V3, but are reduced in strength by ~70%, on average, compared to pre-lesion levels. Monitoring the LPZ activity over time starting one month following the V1 lesion did not reveal systematic changes in BOLD signal amplitude. Surprisingly, the retinotopic organization inside the LPZ of areas V2, V3 remained similar to that of the non-lesioned hemisphere, suggesting that LPZ activation in V2, V3 is not the result of input arising from nearby (non-lesioned) V1 cortex. Electrophysiology recordings of multi-unit activity corroborated the BOLD observations: visually driven multi-unit responses could be elicited inside the V2 LPZ, even when the visual stimulus was entirely contained within the scotoma induced by the V1 lesion. Restricting the stimulus to the intact visual hemi-field produced no significant BOLD modulation inside the V2, V3 LPZs. We conclude that the observed activity patterns are largely mediated by parallel, V1-bypassing, subcortical pathways that can activate areas V2 and V3 in the absence of V1 input. Such pathways may contribute to the behavioral phenomenon of blindsight.},
web_url = {http://www.plosone.org/article/fetchObjectAttachment.action;jsessionid=0A5232F6405DC5F1482FC1AB5827A3AD?uri=info%3Adoi%2F10.1371%2Fjournal.pone.0005527&representation=PDF},
state = {published},
DOI = {10.1371/journal.pone.0005527},
EPUB = {e5527},
author = {Schmid MC{mschmid}, Panagiotaropoulos T{theofanis}{Department Physiology of Cognitive Processes}, Augath MA{mark}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Smirnakis SM{stelios}}
}

@Article{ 5507,
title = {Learning of a T-maze by rat pups when contact with the mother is either permitted or denied},
journal = {Neurobiology of Learning and Memory},
year = {2009},
month = {1},
volume = {91},
number = {1},
pages = {2-12},
abstract = {Mother–pup interactions constitute an important component of environmental stimulation of the offspring during the neonatal period. Employing maternal contact as either a positive reinforcer or, its denial, as a frustrative, non-rewarding stimulus, we developed a novel experimental paradigm involving learning by rat neonates of a T-maze. When trained under the reward of maternal contact during postnatal days 10–13 Wistar rat pups learned the choice leading to the mother in a T-maze. When tested 2 h later, in the absence of the mother, pups showed a clear preference for the arm of the T-maze leading to the position of the mother during training. Furthermore, pups receiving the expected reward of maternal contact had higher numbers of c-Fos immunopositive cells in the dorsal striatum compared to either naïve or pups denied the expected reward. The above behavioral and cellular results indicate that pups receiving the expected reward developed a procedural-like memory. When trained under frustrative non-rewar
d pups learned to make the correct choice in the T-maze, albeit less efficiently than pups receiving the expected reward. Following this training condition c-Fos immunohistochemistry revealed increased activation of the CA1 area of the hippocampus and the orbitofrontal cortex. Expression of the information learned by the pups denied the expected reward was contingent upon the presence of the mother in the experimental setup in exactly the same configuration as during the training.},
web_url = {http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6WNM-4TTM381-3-C&_cdi=6966&_user=29041&_orig=search&_coverDate=01%2F31%2F2009&_sk=999089998&view=c&wchp=dGLzVlz-zSkWz&md5=6b99655e3f950274a7bff11a27ca4a4b&ie=/sdarticle.pdf},
state = {published},
DOI = {10.1016/j.nlm.2008.09.007},
author = {Panagiotaropoulos T{theofanis}, Diamantopoulou A, Stamatakis A, Dimitropoulou M and Stylianopoulou F}
}

@Article{ 5449,
title = {Impairment of learning and memory in TAG-1 deficient mice associated with shorter CNS internodes and disrupted juxtaparanodes.},
journal = {Molecular and Cellular Neuroscience},
year = {2008},
month = {10},
volume = {39},
number = {3},
pages = {478-490},
abstract = {The cell adhesion molecule TAG-1 is expressed by neurons and glial cells and plays a role in axon outgrowth, migration and fasciculation during development. TAG-1 is also required for the clustering of Kv1.1/1.2 potassium channels and Caspr2 at the juxtaparanodes of myelinated fibers. Behavioral examination of TAG-1 deficient mice (Tag-1−/−) showed cognitive impairments in the Morris water maze and novel object recognition tests, reduced spontaneous motor activity, abnormal gait coordination and increased response latency to noxious stimulation. Investigation at the molecular level revealed impaired juxtaparanodal clustering of Caspr2 and Kv1.1/1.2 in the hippocampus, entorhinal cortex, cerebellum and olfactory bulb, with diffusion into the internode. Caspr2 and Kv1.1 levels were reduced in the cerebellum and olfactory bulb. Moreover, Tag-1−/− mice had shorter internodes in the cerebral and cere
bellar white mat
ter. The detected molecular alterations may account for the behavioural deficits and hyperexcitability in these animals.},
web_url = {http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6WNB-4T5TPMB-2-19&_cdi=6958&_user=29041&_orig=browse&_coverDate=08%2F09%2F2008&_sk=999999999&view=c&wchp=dGLzVzz-zSkWz&md5=8bf},
state = {published},
DOI = {10.1016/j.mcn.2008.07.025},
author = {Savvaki M, Panagiotaropoulos T{theofanis}, Stamatakis A, Sargiannidou I, Karatzioula P, Watanabe K, Stylianopoulou F, Karagogeos D and Kleopa KA}
}

@Article{ 5448,
title = {Effect of neonatal handling on adult rat spatial learning and memory following acute stress},
journal = {Stress},
year = {2008},
month = {6},
volume = {11},
number = {2},
pages = {148-159},
web_url = {http://www.informaworld.com/smpp/ftinterface~content=a786934460~fulltext=713240930},
state = {published},
DOI = {10.1080/10253890701653039},
author = {Stamatakis A, Pondiki S, Kitraki E, Diamantopoulou A, Panagiotaropoulos T{theofanis}, Raftogianni A and Stylianopoulou F}
}

@Article{ 5447,
title = {Anatomical landmarks: Dimensions of the mastoid air cell system in the Mediterranean population. Our experience from the anatomy of 298 temporal bones.},
journal = {Anatomical Science International},
year = {2007},
month = {9},
volume = {82},
number = {3},
pages = {139-146},
abstract = {The mastoid apophysis originates from a recent phylogenetic formation, associated with the standing attitude and it is currently considered as an evolution of the bone super-structures. The aim of the present study was to measure the diameters of the mastoid and the temporal bone in the Greek adult population. A total of 298 temporal bones from 149 cadavers (74 male, 75 female) were examined. The distances between six landmarks were measured by means of a pachymeter on both vertical and transverse axes of the mastoids and the temporal bone. The estimated mean values for each dimension were as follows: vertical diameter, 2.37 ± 0.42 cm; transverse diameter, 2.33 ± 0.51 cm; anterior margin, 2.12 ± 0.67 cm; posterior margin, 1.96 ± 0.55 cm; oblong diameter, 10.30 ± 0.60 cm; while the mean distance between the mastoid apex and mandibular fossa calva was 3.67 ± 0.35 cm. Gender differences were detected for the vertical (P < 0.001), the transverse diameter of the mastoid (P < 0.001), the anterior (P < 0.001) and the posterior margin of the mastoid (P < 0.001). In both genders, the vertical diameter of the mastoid was positively correlated with the transverse diameter, as well as with its anterior and posterior margins. In the present study, direct measurements of the mastoid and temporal bone in a Mediterranean population are reported. This description may facilitate a more accurate surgical approach to the temporal bone structures.},
web_url = {http://www3.interscience.wiley.com/journal/118536975/abstract},
state = {published},
DOI = {10.1111/j.1447-073X.2007.00175.x},
author = {Manolis E, Fillipou D, Theocharis S, Panagiotaropoulos T{theofanis}, Lappas D and Mompheratou E}
}

@Article{ 5513,
title = {Tissue concentration of transforming growth factor beta1 and basic fibroblast growth factor in skin wounds created with a CO2 laser and scalpel: a comparative experimental study, using an animal model of skin resurfacing.},
journal = {Wound Repair and Regeneration},
year = {2007},
month = {4},
volume = {15},
number = {2},
pages = {252-257},
web_url = {http://www3.interscience.wiley.com/cgi-bin/fulltext/118514204/PDFSTART},
state = {published},
DOI = {10.1111/j.1524-475X.2007.00212.x},
author = {Manolis EN, Kaklamanos IG, Spanakis N, Fillipou DK, Panagiotaropoulos T{theofanis}, Tsakris A and Siomos K}
}

@Article{ 5446,
title = {Cellular mechanisms underlying the effects of an early experience on cognitive abilities and affective states.},
journal = {Ann Gen Psychiatry},
year = {2005},
month = {4},
volume = {4},
number = {1},
pages = {8-8},
web_url = {http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=15876359},
state = {published},
author = {Garoflos T, Panagiotaropoulos T{theofanis}, Pondiki S, Stamatakis A, Philippidis E and Stylianopoulou F}
}

@Article{ 5445,
title = {Neonatal handling and gender modulate brain monoamines and plasma corticosterone levels following repeated stressors in adulthood.},
journal = {Neuroendocrinology},
year = {2004},
month = {12},
volume = {80},
number = {3},
pages = {181},
web_url = {http://content.karger.com/produktedb/produkte.asp?typ=fulltext&file=NEN2004080003181},
state = {published},
author = {Panagiotaropoulos T{theofanis}, Pondiki S, Papaioannou A, Alikaridis F, Stamatakis A, Gerozissis K and Stylianopoulou F}
}

@Article{ 5444,
title = {Effect of neonatal handling and sex on basal and chronic stress-induced corticosterone and leptin secretion.},
journal = {Neuroendocrinology},
year = {2004},
month = {2},
volume = {79},
number = {2},
pages = {109},
web_url = {http://content.karger.com/produktedb/produkte.asp?typ=fulltext&file=NEN2004079002109},
state = {published},
author = {Panagiotaropoulos T{theofanis}, Papaioannou A, Pondiki S, Prokopiou A, Stylianopoulou F and Gerozissis K}
}

@Poster{ BesserveBPCKTPL2012,
title = {Identifying endogenous rhythmic spatio-temporal patterns in micro-electrode array recordings},
year = {2012},
month = {2},
volume = {9},
pages = {114-115},
abstract = {Microelectrode arrays are a privileged recording modality to study neural processes with a very fine spatial and
temporal resolution. They capture the activity of small populations and permit assessment of synergistic interactions
between cells. Patterns of rhythmic ongoing activity are of particular interest because they reflect the
intrinsic dynamics of neural populations and the way such dynamics may optimize the processing of incoming
information. In this study, we identify the various coherent spatio-temporal patterns of rhythmic activity occurring
across time using a two steps approach. First, signals were bandpass filtered in a relevant frequency band and
subsequently Hilbert-transformed. Second, the complex patterns of activity occurring across time were clustered
using a graph cut algorithm based on a phase shift invariant similarity measure. This invariance is a key-property
of our approach to isolate wave propagation phenomena. We apply our method to Local Field Potentials recorded
in the inferior convexity of the Prefrontal Cortex (icPFC) in two anesthetized macaques using a multi electrode array.
We found a dominant travelling wave pattern in the beta band (15-25Hz), propagating along the ventral-dorsal
plane, emerging and vanishing across time both in the absence of visual stimulation (spontaneous activity) and
during binocular stimulation with movie clips. By computing mutual information, we showed that the amplitude of
this wave actually carries sensory information during the presentation of several movies. Altogether, our analysis
provides evidence for travelling wave phenomena reflecting the distributed computation in icPFC, which is known
to be involved in higher order sensory processing. More generally, our approach enables the unsupervised analysis
of the complex spatio-temporal neural dynamics in ongoing signals, providing key information to understand
cooperative mechanisms in spatially distributed neural populations.},
web_url = {http://www.cosyne.org/c/index.php?title=Cosyne_12},
event_name = {9th Annual Computational and Systems Neuroscience Meeting (Cosyne 2012)},
event_place = {Salt Lake City, UT, USA},
state = {published},
author = {Besserve M{besserve}{Department Empirical Inference}{Department Physiology of Cognitive Processes}, Panagiotaropoulos T{theofanis}{Department Physiology of Cognitive Processes}, Crocker B{bcrocker}{Department Physiology of Cognitive Processes}, Kapoor V{vishal}{Department Physiology of Cognitive Processes}, Tolias A{atolias}{Department Physiology of Cognitive Processes}, Panzeri S{stefano} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ CrockerKPLP2011,
title = {Low frequency local field potentials in the inferior convexity of the macaque prefrontal cortex convey visual information during anesthesia},
year = {2011},
month = {11},
volume = {41},
number = {484.13},
abstract = {The inferior convexity of the macaque prefrontal cortex (icPFC), the cortical area anterior to the arcuate and inferior to the principal sulcus, consists the final endpoint of the ventral visual stream. It has been suggested that the icPFC is involved in higher order processing of non spatial visual information like stimulus selection, attention and working memory. However, early findings demonstrated that spiking activity in the icPFC is also modulated by visual stimulation during anesthesia. Here we used multi-electrode recordings to study in more detail the neural coding of visual information as well as the spatial distribution of this information in the icPFC of the anesthetized macaque. We recorded local field potentials (LFP) and multi and single unit spiking activity, and calculated the Shannon (mutual) information between these neurophysiological signals and a dynamic movie stimulus. We found that the phase of low frequency (1-10Hz) local field potentials (LFP) conveyed significant visual information about the movie. Significant information was also conveyed by the energy of the low frequency (1-10Hz) LFP. However the mutual information between the energy of the 1-10Hz LFP and the movie was an order of a magnitude less than the information conveyed by the phase. Information in the LFP phase was distributed evenly across all recorded sites, with almost all channels lying between 50% and 150% of the average amount of information. However, the information carried by the LFP amplitude was highly clustered around a small group of electrodes. Almost half of the recorded sites carried less than 50% of the mean information across electrodes, and around 15 recorded sites had more than 3 times the average information. High frequency LFP phase and energy were highly variable across repeated presentations of the movie and were thus non-informative. Similarly, multi unit and single unit spiking activity pattern or rate codes conveyed no information about the movie. Our results show that input and intracortical processing in the icPFC during anesthesia conveys significant information about dynamic visual stimuli.},
web_url = {http://www.sfn.org/am2011/},
event_name = {41st Annual Meeting of the Society for Neuroscience (Neuroscience 2011)},
event_place = {Washington, DC, USA},
state = {published},
author = {Crocker B{bcrocker}{Department Physiology of Cognitive Processes}, Kapoor V{vishal}{Department Physiology of Cognitive Processes}, Panzeri S{stefano}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Panagiotaropoulos T{theofanis}{Department Physiology of Cognitive Processes}}
}

@Poster{ PanagiotaropoulosBCKTPL2011,
title = {Spatiotemporal mapping of rhythmic activity in the inferior convexity of the macaque prefrontal cortex},
year = {2011},
month = {11},
volume = {41},
number = {239.15},
abstract = {The inferior convexity of the macaque prefrontal cortex (icPFC) is known to be involved in higher order processing of sensory information mediating stimulus selection, attention and working memory. Until now, the vast majority of electrophysiological investigations of the icPFC employed single electrode recordings. As a result, relatively little is known about the spatiotemporal structure of neuronal activity in this cortical area. Here we study in detail the spatiotemporal properties of local field potentials (LFP's) in the icPFC using multi electrode recordings during anesthesia. We computed the LFP-LFP coherence as a function of frequency for thousands of pairs of simultaneously recorded sites anterior to the arcuate and inferior to the principal sulcus. We observed two distinct peaks of coherent oscillatory activity between approximately 4-10 and 15-25 Hz. We then quantified the instantaneous phase of these frequency bands using the Hilbert transform and found robust phase gradients across recording sites. The dependency of the phase on the spatial location reflects the existence of traveling waves of electrical activity in the icPFC. The dominant axis of these traveling waves roughly followed the ventral-dorsal plane. Preliminary results show that repeated visual stimulation with a 10s movie had no dramatic effect on the spatial structure of the traveling waves. Traveling waves of electrical activity in the icPFC could reflect highly organized cortical processing in this area of prefrontal cortex.},
web_url = {http://www.sfn.org/am2011/},
event_name = {41st Annual Meeting of the Society for Neuroscience (Neuroscience 2011)},
event_place = {Washington, DC, USA},
state = {published},
author = {Panagiotaropoulos T{theofanis}{Department Physiology of Cognitive Processes}, Besserve M{besserve}{Department Empirical Inference}{Department Physiology of Cognitive Processes}, Crocker B{bcrocker}{Department Physiology of Cognitive Processes}, Kapoor V{vishal}{Department Physiology of Cognitive Processes}, Tolias AS{atolias}{Department Physiology of Cognitive Processes}, Panzeri S{stefano} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ 6817,
title = {Reduction of Correlated Noise in the Macaque Prefrontal Cortex during Conscious Visual Perception},
year = {2010},
month = {6},
volume = {2010},
pages = {82},
abstract = {The cortical mechanisms mediating visual awareness are thought to exploit a large
population of similarly tuned neurons explicitly representing a perceptually dominant visual
pattern through changes in its mean firing rate. However, inherent limitations of population
rate coding schemes such as noise detected in the correlated response variability across
neurons could constrict the encoding power of such a cortical network and thus decrease
the probability of this encoding strategy. Studying the differences in the noise correlation
structure of a tuned population between purely sensory visual stimulation subjective visual
perception could thus provide fundamental insights into the mechanisms of conscious visual
perception. Here we show that in the macaque prefrontal cortex perceptual dominance
under conditions of visual rivalry is accompanied by decorrelated discharges across neurons
sensory tuned to the dominant stimulus, compared to their significantly correlated
fluctuations when the same stimulus is perceived without competition. We propose that
noise decorrelation in prefrontal cortical circuits is optimal for achieving perceptual
dominance during visual awareness by substantially improving the encoding accuracy of the
dominant neuronal ensemble. Our findings also provide the first electrophysiological
demonstration of the contribution of prefrontal cortex to visual consciousness, a hypothesis
previously suggested by theoretical models as well as human functional imaging studies.},
web_url = {http://www.areadne.org/2010/home.html},
editor = {Hatsopoulos, N. G., S. Pezaris},
event_name = {AREADNE 2010: Research in Encoding And Decoding of Neural Ensembles},
event_place = {Santorini, Greece},
state = {published},
author = {Panagiotaropoulos T{theofanis}{Department Physiology of Cognitive Processes}, Kapoor V{vishal}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ KapoorWPKL2009,
title = {Comparing inter-ocular switch and classical binocular rivalry in the human brain using EEG},
year = {2009},
month = {11},
volume = {10},
number = {3},
pages = {22},
abstract = {When disparate visual stimuli are presented to corresponding retinal locations, perception fluctuates between the presented stimuli. This phenomenon, called binocular rivalry, is an exquisite tool to dissociate sensory stimulation from visual perception. It has therefore been extensively used for studying the neural correlates of visual awareness. Initial theories have
tried to explain binocular rivalry by hypothesizing the resolution of competition in V1 through inhibitory interactions between monocular neurons. However, inter-ocular switch rivalry, a paradigm where the rivaling stimuli are rapidly exchanged between the eyes also results in stable percepts that span several swaps of the visual stimuli. This has demonstrated that competition also involves higher-level stimulus representations, and not just eye based sensory information. In this study, we compared the electrophysiological correlates underlying
stable visual percepts during inter-ocular switch and binocular rivalry. Delineating the differences
and similarities between the two paradigms of rivalry will provide us with valuable information on the nature of competition during incongruent visual stimulation. We recorded EEGs while human subjects experienced inter-ocular switch and classical binocular rivalry elicited with dichoptic presentation of orthogonally oriented sinusoidal gratings. The subjects reported their percepts via button presses. We extracted and analyzed trials, where subjects
reported at least one second long stable percepts. During this time window, we assessed the normalized spectrogram to visualize mean event-related changes in spectral power across a broad frequency range (1 - 45 Hz). We observed a strong and sustained increase in spectral power between 12 - 30 Hz across the two conditions approximately 300 ms following the reported perceptual switch. Low Resolution Brain Electromagnetic Tomography (LORETA) was used to localize the cortical sources of the observed changes. The maps of the localized cortical sources of this increase in the spectral power during inter-ocular switch and binocular
rivalry were remarkably similar and showed no significant differences. We therefore propose that both types of rivalry have similar EEG correlates in the 12 - 30 Hz frequency band during a stable visual percept.
22},
web_url = {http://www.neuroschool-tuebingen-nena.de/},
event_name = {10th Conference of Junior Neuroscientists of Tübingen (NeNa 2009)},
event_place = {Ellwangen, Germany},
state = {published},
author = {Kapoor V{vishal}{Department Physiology of Cognitive Processes}, Whittingstall K{kevin}{Department Physiology of Cognitive Processes}, Panagiotaropoulos T{theofanis}{Department Physiology of Cognitive Processes}, Keliris G{george}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ 6286,
title = {Comparing inter-ocular switch and classical binocular rivalry in the human brain using eeg},
year = {2009},
month = {10},
volume = {39},
number = {380.11},
abstract = {When disparate visual stimuli are presented to corresponding retinal locations in the two eyes, perception fluctuates between the presented stimuli. This phenomenon, called binocular rivalry, is an exquisite tool to dissociate sensory stimulation from visual perception. It has therefore been extensively used for studying the neural correlates of visual awareness. Initial theories have tried to explain binocular rivalry by hypothesizing the resolution of competition in V1 through inhibitory interactions between monocular neurons. However, inter-ocular switch rivalry, a paradigm where the rivaling stimuli are rapidly exchanged between the eyes also results in stable percepts that span several swaps of the visual stimuli. This has demonstrated that competition also involves higher level stimulus representations, and not just eye based sensory information. In this study, we compared the electrophysiological correlates underlying stable visual percepts during inter-ocular switch and classical binocular rivalry. Delineating the differences and similarities between the two paradigms of rivalry will provide us with valuable information on the nature of competition during incongruent visual stimulation. We recorded EEGs while human subjects experienced inter-ocular switch and classical binocular rivalry elicited with dichoptic presentation of orthogonally oriented sinusoidal gratings. The subjects reported their percepts via button presses. We extracted and analyzed trials, where subjects reported at least one second long stable percepts. During this time window, we assessed the normalized spectrogram to visualize mean event-related changes in spectral power across a broad frequency range (1-45 Hz). We observed a strong and sustained increase in spectral power between 12-30 Hz across the two conditions approximately 300 ms following the reported perceptual switch. Low Resolution Brain Electromagnetic Tomography (LORETA) was used to localize the cortical sources of the observed changes. The maps of the localized cortical sources of this increase in the spectral power during inter-ocular switch and binocular rivalry were remarkably similar and showed no significant differences. We therefore propose that both types of rivalry have similar EEG correlates in the 12-30 Hz frequency band during a stable visual percept.},
web_url = {http://www.abstractsonline.com/Plan/ViewAbstract.aspx?sKey=f5dec3fb-2bb6-482d-8553-db756136f1a1&cKey=a119d583-ca30-4a52-801f-b1aed085e303},
event_name = {39th Annual Meeting of the Society for Neuroscience (Neuroscience 2009)},
event_place = {Chicago, IL, USA},
state = {published},
author = {Kapoor V{vishal}{Department Physiology of Cognitive Processes}, Whittingstall K{kevin}{Department Physiology of Cognitive Processes}, Panagiotaropoulos T{theofanis}{Department Physiology of Cognitive Processes}, Keliris GA{george}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ 6281,
title = {Dynamical changes in functional circuitry of the macaque prefrontal cortex mediating a perceptual switch},
year = {2009},
month = {10},
volume = {39},
number = {622.17},
abstract = {Binocular rivalry (BR) has been successfully combined with extracellular electrophysiological recordings in awake, behaving macaques to study the cortical mechanisms of visual conscious experience. The contribution of different cortical areas to visual awareness is commonly determined by reporting the percentage of neurons modulated, in each area, in accordance with the percept. However, in order to obtain a detailed understanding of the cortical mechanisms mediating subjective visual perception it is likely that valuable insights could be gained by studying the neuronal interactions within pools of neurons sharing similar stimulus preference. One of the most commonly studied forms of neuronal interaction is noise (or spike count) correlations i.e the correlation in the variability around the mean of trial by trial spike counts between pairs of simultaneously recorded neurons. In this study we used binocular flash suppression (BFS), a highly controlled variant of BR, to explore the neuronal correlates of visual awareness in the inferior prefrontal convexity (icPFC) of the macaque brain while simultaneously recording pairs of neurons preferring the same visual stimulus. We report that the perception of a stimulus under rivalrous conditions is accompanied by a drastic decrease in noise correlations between neurons sharing a similar preference to this stimulus compared to noise correlations when the same stimulus is perceived without competition. We propose that this decorrelation of neuronal discharges during visual competition is optimal for rivalrous perception since it renders the dominant neural population representing the perceived stimulus more sensitive to it by increasing the signal to noise ratio conveyed by signal averaging. This is in agreement with local correlation models that predict enhanced information coding as a result of decorrelated noise between neurons with similar tuning functions. Similar studies in other visual cortical areas during rivalrous visual stimulation could show whether reduction of correlated noise is observed throughout the ventral visual stream or it is a unique property of the ventral prefrontal cortex.},
web_url = {http://www.abstractsonline.com/Plan/ViewAbstract.aspx?sKey=abbf38a3-9e54-4ec7-a483-d333079a2cc8&cKey=97c91e04-79b8-454d-817e-7ac52c33e4e3},
event_name = {39th Annual Meeting of the Society for Neuroscience (Neuroscience 2009)},
event_place = {Chicago, IL, USA},
state = {published},
author = {Panagiotaropoulos T{theofanis}{Department Physiology of Cognitive Processes}, Komlos M{marcell}, Kapoor V{vishal}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ PanagiotaropoulosKKTL2009,
title = {High frequency local field potentials and multi unit activity reflect visual awareness in the macaque prefrontal cortex},
journal = {Frontiers in Behavioral Neuroscience},
year = {2009},
month = {9},
volume = {Conference Abstract: 41st European Brain and Behaviour Society Meeting},
abstract = {Binocular rivalry (BR) has been successfully combined with extracellular electrophysiological recordings in awake, behaving macaques to study the cortical mechanisms of subjective visual perception. Here we used binocular flash suppression (BFS), a highly controlled variant of BR, to explore the neuronal correlates of visual awareness in the inferior prefrontal convexity (icPFC) of the macaque brain while simultaneously recording multi unit activity (MUA) and local field potentials (LFP). We found that MUA was perceptually modulated in 67% of the visually selective recording sites. During BFS in 92% of MUA modulated sites we observed higher firing rates when the preferred stimulus was perceived. An explicit representation of the perceptually dominant stimulus was also provided by the power modulation of high frequency LFP’s only at the MUA modulated sites. Specifically, sensory selectivity of the LFP power increased as a function of frequency with the highest selectivity observed between 150 and 450Hz. The same pattern in LFP power selectivity was observed when the preferred stimulus was perceived during BFS. A correlation analysis between MUA and LFP power selectivity showed significant correlation in sensory selectivity for frequencies >60Hz that saturated at 150Hz and followed the same pattern during BFS.
While spikes measure cortical output, LFP’s are thought to reflect input and intracortical processing in a given cortical area. According to this scheme our results suggest that icPFC sites providing perceptually modulated output are also the sites that receive and process a representation of the perceived stimulus during BFS. Inferior temporal cortex (IT) output is also known to reflect the perceived stimulus during ambiguous visual stimulation and could thus be the source of the modulated icPFC input reflected in the LFP’s. Our results suggest a highly organized network involving IT and icPFC that mediates visual awareness during subjective visual perception.},
web_url = {http://www.frontiersin.org/10.3389/conf.neuro.08.2009.09.251/event_abstract},
event_name = {41st European Brain and Behaviour Society Meeting},
event_place = {Rhodos, Greece},
state = {published},
DOI = {10.3389/conf.neuro.08.2009.09.251},
author = {Panagiotaropoulos T{theofanis}{Department Physiology of Cognitive Processes}, Kapoor V{vishal}{Department Physiology of Cognitive Processes}, Keliris GA{george}{Department Physiology of Cognitive Processes}, Tolias A{atolias}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ 5443,
title = {Neurophysiological substrates of visual awareness in the macaque prefrontal cortex},
year = {2008},
month = {7},
volume = {6},
number = {220.12},
abstract = {Human fMRI studies during binocular rivalry have demonstrated an involvement of prefrontal cortex (PFC) in the processing of subjective visual perception. In this study we used binocular flash suppression, a version of binocular rivalry that permits the robust induction of a visual percept, to study the neuronal correlates of visual awareness in the macaque prefrontal cortex (PFC) and specifically in the inferior prefrontal convexity. We found that the firing rate of almost 70% of the visually selective neurons closely followed the induced visual percept. This percentage is significantly higher than the respective percentage of perceptually modulated cells found in the striate and extrastriate visual cortex (V1, V2 and V4) but smaller than that found in the inferior temporal cortex (IT) (almost 90%). Interestingly, we observed that the neuronal responses following a perceptual alternation were transient, similar to the transient BOLD response observed during perceptual transitions in the human binocular rivalry fMRI studies. Our finding provides further evidence in support of a role of higher brain areas in processing an explicit perceptual representation during ambiguous visual stimulation. In addition, it points to a potential neuronal network consisting of perceptually modulated cells in IT and PFC that process an explicit representation of a visual percept. The existence of such a network is not surprising since area TE of inferior temporal cortex is anatomically connected to the inferior convexity (areas 12/45) through feedforward and feedback pathways.
Finally, in an effort to explore whether the perceptual modulation observed in primary visual cortex (V1) is influenced by a feedback signal from PFC we will also present data from simultaneous PFC and V1 neurophysiological recordings during binocular flash suppression.},
web_url = {http://fens2008.neurosciences.asso.fr/},
event_name = {6th Forum of European Neuroscience (FENS 2008)},
event_place = {Geneva, Switzerland},
state = {published},
author = {Panagiotaropoulos T{theofanis}{Department Physiology of Cognitive Processes}, Kapoor V{vishal}{Department Physiology of Cognitive Processes}, Keliris GA{george}{Department Physiology of Cognitive Processes}, Tolias A{atolias}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ 5442,
title = {Single units reflect visual awareness in the macaque prefrontal cortex},
year = {2008},
month = {6},
pages = {80},
web_url = {http://www.areadne.org/2008/home.html},
event_name = {AREADNE 2008: Research in Encoding and Decoding of Neural Ensembles},
event_place = {Santorini, Greece},
state = {published},
author = {Panagiotaropoulos T{theofanis}{Department Physiology of Cognitive Processes}, Kapoor V{vishal}{Department Physiology of Cognitive Processes}, Keliris GA{george}{Department Physiology of Cognitive Processes}, Tolias A{atolias}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Conference{ PanagiotaropoulosBL2012,
title = {Beta oscillations propagate as traveling waves in the macaque prefrontal cortex},
year = {2012},
month = {10},
volume = {42},
number = {413.03},
abstract = {Despite significant progress in understanding functional parcellation of the primate prefrontal cortex (PFC) it is currently unknown whether an intrinsic mechanism could dynamically coordinate activity between these functionally specialized sub-regions. Such a mechanism could be reflected in spatially organized rhythmic activity that is macroscopically observed as complex, rhythmic spatio-temporal patterns. Here, we used multielectrode arrays (Utah arrays) and recorded neural activity from a large area (16mm2) of the macaque lateral PFC during anesthesia in order to explore spatio-temporal patterns in the default state of the prefrontal cortical network. We recorded local field potentials (LFP's) (1-200Hz) and found that the spatial coherence of oscillatory activity exhibited a distinctive peak in the "beta" (15-30 Hz) frequency range during resting state but also during visual stimulation with dynamic movie stimuli. We then used the Hilbert transform to obtain the analytic signal and evaluated the two-dimensional instantaneous phase maps. We observed consistent phase gradients in the "beta" frequency range that formed complex, dynamic patterns, suggesting propagation of oscillatory activity across the cortical surface. A graph cut algorithm based on a measure of phase shift invariant similarity was used to cluster these spatio-temporal patterns. Our analysis revealed a dominant travelling wave pattern in the "beta" band, propagating along the ventral-dorsal plane and replaced by less frequent, less dominant patterns both in the absence of visual stimulation (spontaneous activity) and during stimulation with movie clips. By estimating mutual information, we found that the amplitude of this wave conveyed sensory information during the presentation of several movies. Our data show that travelling wave phenomena are suggestive of highly coordinated activity in the PFC, a cortical area known to be involved in higher order sensory processing. These traveling waves of oscillatory neural activity are modulated by sensory input and could provide a functional substrate for coordinating activity across different subregions of the PFC. Finally, our approach enables the unsupervised analysis of the complex spatio-temporal neural dynamics in ongoing oscillatory signals, providing an analytical framework to understand cooperative mechanisms in spatially distributed neural populations.},
web_url = {http://www.sfn.org/am2012/},
event_name = {42nd Annual Meeting of the Society for Neuroscience (Neuroscience 2012)},
event_place = {New Orleans, LA, USA},
state = {published},
author = {Panagiotaropoulos T{theofanis}{Department Physiology of Cognitive Processes}, Besserve M{besserve}{Department Empirical Inference}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Conference{ 5290,
title = {On the neural mechanisms of binocular rivalry},
journal = {Frontiers in Human Neuroscience},
year = {2008},
month = {9},
day = {4},
volume = {Conference Abstract: 10th International Conference on Cognitive Neuroscience},
abstract = {Binocular rivalry is scientifically attractive because it allows the study of an entirely subjective experience using objective measurements: During rivalry the visual percept changes dramatically – from one image to another – while the two stimuli presented to the eyes remain constant. There are at least two aspects whose neural origin would be worthwhile understanding: 1. The mechanisms that lead to the stochastic, spontaneous, and sometimes abrupt alternations of the percept from one stimulus to the other; 2. The mechanisms that keep one stimulus dominant, perceived, and the other suppressed. Previous psychophysical studies have elegantly demonstrated that both monocular and binocular sites contribute to perceptual alternations and to perceptual dominance. Recordings from single neurons, from monocular cells in V1 to cells in the prefrontal cortex show signals representing both the suppressed as well as the dominant stimuli. The proportion of neurons exhibiting percept-modulated responses rises from V1, through V4/V5, IT to prefrontal cortex. Additionally, some studies have reported that certain bands of local field potentials in V1 contain more information about the percept than spikes, while fMRI results in the human brain even show perceptual modulations in the LGN. Like psychophysics, physiology points toward a potentially complex interaction of several neural sites involved in rivalry. We will present the latest recordings from hundreds of neurons in V1, as well as initial recordings from prefrontal cortex. We will mainly focus however, on new psychophysical results shedding light on the eye-versus-percept debate. These results suggest a time-dependence of eye and percept contributions in binocular rivalry. During a dominance period, it appears that it is initially a given monocular channel that has major influence on dominance, regardless of the percept. Over time, this reverses, with image-related, eye-independent processes increasingly controlling any perceptual switch. Our results lead us to suggest that monocular effects – as observed here and in previous studies – may directly depend on higher-level effects and vice versa, because monocular as well as higher-level perceptual influences on dominance vary in parallel but with opposite signs over time. Therefore, the monocular and binocular effects observed in binocular rivalry may reflect different ends of a single process affecting several neural stages. A potential model could be that an initially strong stimulus representation is stabilized by a reinforcing, noise-reducing loop between binocular and monocular stages. As the stability of this process weakens, both the monocular channel loses influence, and the binocular stimulus representation weakens, increasingly favoring a perceptual switch.},
web_url = {http://www.frontiersin.org/10.3389/conf.neuro.09.2009.01.048/event_abstract},
event_name = {10th International Conference on Cognitive Neurosciences (ICON 2008)},
event_place = {Bodrum, Turkey},
state = {published},
DOI = {10.3389/conf.neuro.09.2009.01.048},
author = {Bartels A{abartels}{Department Physiology of Cognitive Processes}, Panagiotaropoulos T{theofanis}{Department Physiology of Cognitive Processes}, Keliris GA{george}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Conference{ 4993,
title = {Areas V2 and V3 remain active and retinotopically organized in the absence of direct V1 input},
year = {2007},
month = {11},
volume = {37},
number = {122.2},
abstract = {The presence of focal lesions in primary visual cortex (V1) provides an opportunity to study the role of extra-geniculo-striate pathways for activating extra-striate areas. Single unit measurements reported inactivation of more than 95% of V2 and V3 neurons following reversible cooling of V1 (Girard and Bullier, 1989; Girard et al., 1991a; Schiller et al., 1974). Here we used fMRI in anesthetized monkeys (Logothetis et al., 1999) to study the organization and activation levels of areas V2 and V3 from one month up to 681 days following a focal V1 aspiration lesion. We find that the strength of stimulus driven BOLD activation inside the area V2, V3 lesion projection zones (LPZ) drops by ~70 % compared to baseline and shows no systematic change between the first month post-lesioning and the maximum time studied. Interestingly, the retinotopic organization of the area V2, V3 LPZs remains similar to pre-lesion maps. Restricting the stimulus to the non-lesioned visual field is not effective in activating the ipsi-lesional LPZ ruling out the possibility that callosal input mediates the observed pattern of responses. We conclude that residual activity in V2 and V3 devoid of V1 input is likely due to parallel subcortical pathways possibly contributing to the behavioral phenomenon of blindsight.
Figure Caption:
Eccentricity map of the right visual cortex of a rhesus macaque 681 days post-V1 lesioning. Visual stimulation was performed using a rotating checkerboard ring stimulus (gray inset) expanding in time and space which resulted in a phase shift of the BOLD response (retinotopic mapping). Voxels with similar phase values are color-coded (colored inset) and superimposed on the anatomical flat map. The lesion in V1 extends from ~2.3 to 7°, and from the external calcarine to the lunate (total area: 235 mm²). The lesion projection zones (LPZ) of dorsal V2 and V3 are outlined using retinotopic correspondence criteria. Despite the absence of retinotopically},
web_url = {http://www.sfn.org/am2007/},
event_name = {37th Annual Meeting of the Society for Neuroscience (Neuroscience 2007)},
event_place = {San Diego, CA, USA},
state = {published},
author = {Schmid MC{mschmid}, Panagiotaropoulos T{theofanis}{Department Physiology of Cognitive Processes}, Augath MA{mark}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Smirnakis SM{stelios}}
}