Introduction and Scientific Aims
The neural signature of visual consciousness has been detected in the electrical activity of multiple cortical areas across the visual hierarchy, during tasks that permit a dissociation of purely sensory stimulation from subjective perception. In the past, single unit and local field potential (LFP) recordings were mainly employed to define the contribution of different cortical areas in visual awareness. However, understanding the dynamics of cortical networks during subjective visual perception at a local microcircuit level but also in a global scale could reveal unknown aspects of neural activity that are more directly related to the emergence of visual awareness. Which are then these features of neuronal activity that – if examined at a global scale – may potentially uncover the mechanisms responsible for the subjective experiences that define consciousness? We address these questions using a combination of behavioral, electrophysiological and computational methods.
Converging evidence from psychophysical, functional imaging and electrophysiological studies points to a crucial role of non-sensory, association cortical areas in subjective visual perception. These areas are thought to modulate neuronal activity in primary, sensory and lower associational areas through feedback connections and inter-level interactions in general. The main goal of this project is first to describe the local population dynamics of neural activity in the prefrontal and temporal cortices as well as the corticocortical interactions between these two areas that relate to the behavior of animals reporting what they perceive at any given time. In this first step a detailed understanding of cortical phenomena like intrinsic noise and spatiotemporally organized electrical activity is important, as it can reveal some of the emerging neural properties underlying visual awareness. The findings of these investigations will be the seed for future research of larger networks examined with a combination of imaging and multi-site electrophysiology techniques.
A. Single unit tetrode recordings in the lateral prefrontal cortex.
B. Modulation of neuronal discharges during sensory stimulation and ambiguous visual perception.
C. Utah-multielectrode array recordings in the inferior convexity of the lateral prefrontal cortex.
We use extracellular multielectrode and tetrode electrophysiological recordings coupled with behavioral tasks that introduce ambiguous visual stimulation in macaque monkeys. Monkeys are trained to report their subjective stimulus experience by pulling levers during tasks like binocular rivalry and binocular flash suppression. These paradigms allow a dissociation of sensory stimulation from subjective perception, thus permitting a similar dissociation of the simultaneously recorded neuronal activity. We use single unit and LFP recordings in single sites to probe the contribution of cortical areas to conscious perception. Our neurophysiological data are then used to constrain theoretical models on dynamic complex systems studying the factors that mediate spontaneous perceptual switches. Furthermore, in our effort to better understand the spatiotemporal patterns of spontaneous activity in the areas of interest and how these patterns are modulated during conscious visual perception, we study neural activity with large electrode-arrays that provide high spatial resolution.
Optimization of this methodology is currently done by recording in the prefrontal cortex during anesthesia. Novel analytical tools are also developed to cluster the recorded spatiotemporal patterns of neural activity. Finally, we develop new electrophysiological recording methods that allow excellent single unit isolation and therefore the monitoring of large neuronal populations in areas of the temporal cortex.
Panagiotaropoulos TI, Kapoor V, Logothetis NK. Subjective visual perception: From local processing to emergent phenomena of brain activity. Philos Trans R Soc Lond B Biol Sci (in press)
Panagiotaropoulos TI, Logothetis NK and Keliris GA. (in press) Neural approaches to perceptual organization. in The Handbook of Computational Perceptual Organization (Eds. Gepshtein-Maloney).
Panagiotaropoulos TI, Kapoor V, Logothetis NK. (2013). Desynchronization and rebound of beta oscillations during conscious and unconscious local neuronal processing in the macaque lateral prefrontal cortex. Front Psychol 4:603.
Kapoor V, Krampe E, Klug A, Logothetis NK, Panagiotaropoulos TI. (2013). Development of Tube Tetrodes and a Multi-Tetrode Drive for deep structure electrophysiological recordings in the macaque brain. J Neurosci Methods 216(1):43-8.
Panagiotaropoulos TI and Logothetis NK. (2013). Multistable visual perception as a gateway to the neural correlates of phenomenal consciousness. The scope and limits of neuroscientific analysis. in L. Albertazzi (Ed.) The Handbook of Experimental Phenomenology:Visual Perception of Shape, Space and Appearance (pp 119-144). John Wiley & Sons.
Panagiotaropoulos TI, Kapoor V, Logothetis NK, Deco G. (2013). A common neurodynamical mechanism could mediate externally induced and intrinsically generated transitions in visual awareness. PLoS One 8(1): e53833.
Panagiotaropoulos TI, Besserve M, Logothetis NK. (October 2012). Beta oscillations propagate as traveling waves in the macaque prefrontal cortex. 42nd Annual Meeting of the Society for Neuroscience (Neuroscience 2012),New Orleans, LA, USA.
see Nanosymposium on signal propagation at Neuroscience 2012 meeting co-organized/co-chaired with K. Takahashi, T.Zanos, M. Besserve.
Besserve M, Panagiotaropoulos T, Crocker B, Kapoor V, Tolias AS, Panzeri S, Logothetis NK (March 2012). Identifying endogenous rhythmic spatiotemporal patterns in microelectrode array recordings, 9th Annual Computational and Systems Neuroscience Meeting. Salt Lake City, Utah, USA.
Panagiotaropoulos TI, Besserve M, Crocker B, Kapoor V, Tolias AS, Panzeri S, Logothetis NK. (November 2011). Spatiotemporal mapping of rhythmic activity in the inferior convexity of the macaque prefrontal cortex. 41st Annual Meeting of the Society for Neuroscience (Neuroscience 2011), Washington, DC, USA.
Theodoni P, Panagiotaropoulos TI, Kapoor V, Logothetis NK, and Deco G. (2011). Cortical microcircuit dynamics mediating binocular rivalry: The role of adaptation in inhibition. Front Hum Neurosci 5, 145.
see Special Research Topic in Frontiers in Human Neuroscience - Binocular Rivalry a Gateway to Consciousness (co-hosted with G.A. Keliris, A. Maier and N. Tsuchiya)
Panagiotaropoulos T, Kapoor V, Logothetis NK. (June 2010). Reduction of Correlated Noise in the Macaque Prefrontal Cortex during Conscious Visual Perception. AREADNE Research in Encoding And Decoding of Neural Ensembles, Santorini, Greece.
Schmid MC, Panagiotaropoulos T, Augath MA, Logothetis NK, and Smirnakis SM. (2009). Visually driven activation in macaque areas V2 and V3 without input from the primary visual cortex. PLoS One 4, e5527.
Vishal Kapoor (Binocular Rivalry, PFC-IT interactions and development of tetrode technology)
Britni Crocker (information theoretic analysis of neural signals in the macaque PFC and functional imaging of the PFC)
Theoretical modeling of bistable perception
Computational Neuroscience Group, Universitat Pompeu Fabra, Barcelona, Spain
Spatiotemporal mapping of neuronal activity in the macaque PFC
MPI for Biological Cybernetics, Tubingen, Germany
University of Glasgow, Scotland
Baylor College of Medicine, Department of Neuroscience, Houston, U.S.A
Functional Imaging of the macaque PFC
MPI for Biological Cybernetics, Tubingen, Germany
Our results show that neuronal activity in the lateral prefrontal cortex strongly correlates with subjective visual perception. The responses of small neuronal populations are as selective and perception-driven as those reported in the temporal cortex; therefore the content of conscious visual perception is reliably represented in the neuronal activity of at least two association cortical areAs.
Psychophysical and electrophysiological data are used to constrain dynamic models of bistable perception. The predictions provided by the combination of theoretical and experimental results formulate new experimental questions.
Two monkeys are currently trained to report spontaneous binocular rivalry. The functional interactions between PFC and IT cortex are currently probed during externally induced perceptual switches using binocular flash suppression
Large-scale spatiotemporal patterns of spontaneous and visually driven neuronal activity in the lateral prefrontal cortex are characterized.
We quantify the information conveyed by LFP's and neuronal discharges in the lateral prefrontal cortex during visual stimulation.
MPI for Biological Cybernetics
Spemanstrasse 38, 72076, Tubingen, Germany
2006-2012 Postdoctoral fellow Max Planck Institute for Biological Cybernetics
2005 Phd in Cognitive Science National & Kapodistrian University of Athens.
2002 MSc in Cognitive Science National & Kapodistrian University of Athens.
1999 BA in Psychology Panteion University of Athens.
1997-98 Training in Adolescent Psychopathology Department of Adolescent Psychiatry, General Hospital of Athens G.Gennimatas
Peer-reviewed articles (in chronological order)
articles in preparation
Selected Conference Abstracts
November 2014 California Institute of Technology, Pasadena, U.S.A
January 2013 University of Tübingen, Tübingen, Germany
January 2013 University of Sussex, Sussex, U.K.
October 2012 Society for Neuroscience Meeting, New Orleans, U.S.A
January 2012 Universitat Pompeu Fabra, Barcelona, Spain.
September 2008 Universitat Pompeu Fabra, Barcelona, Spain.
June 2005 University of Crete, Heraklion, Greece.
Μay 2003 9th Pan-Hellenic Conference of Psychology, Rhodes, Greece.
March 2001 21st European Winter Conference on Brain Research, Arc 1800, France.
2006-2012 Max Planck Society Postdoctoral fellowship.
2009 FENS travel award (for participation in the annual meeting of the Society for Neuroscience)
2006 DAAD (Deutscher Akademischer Austauschdienst)
Research grant Enhancement of plasticity of primary visual cortex following retinal lesions.
2003-2006 Greek State Scholarships Foundation
Phd scholarship in Neuroscience
2003 Aristotle award for the best submitted paper: Cellular mechanisms underlying the effects of an early experience on cognitive abilities and affective states. 1st International Congress on Brain and Behavior, Thessaloniki, Greece.
2003 The Vivian Smith Advanced Studies Institute of the International Neuropsychological Society. Travel Award for participation in the Summer Institute: Memory and the Amnesias. Xylokastro, Greece.
2002-2005 National & Kapodistrian University of Athens, Research Grant “Iraklitos”: The effect of frustration of maternal contact on the cognitive function of the rat: Psychobiological mechanisms.
2002 ESF-EURESCO Travel grant for participation in the European Research Conference on Neural Mechanisms of Learning and Memory, Evian, France.
2002 EUROSTERONE Travel grant for participation in the Summer School: Neurobiology of Stress in Health and Disease, Elba, Italy.
2001 Vergina award for the best submitted paper. Interaction between an early experience and gonadal hormones in determining the adaptability of the organism. 1st Congress of the Hellenic Association of Psychophysiology, Thessaloniki, Greece.
2001 Research Grant from French government (Program Platon, dossier No 20012517). Laboratoire Physiopathologie de la Nutrition, Universite Paris VII, CNRS ESA 7059.
Frontiers in Human Neuroscience (Associate Editor)
Ad Hoc Reviewer
Philosophical Transactions of the Royal Society B: Biological Sciences
Frontiers in Human Neuroscience
German National Academy of Sciences (Leopoldina)
Society for Neuroscience (SfN)
Federation of the European Neuroscience Societies (FENS)
Hellenic Society for Neurosciences (HSFN)
2002-2005 Teaching assistant Graduate Program in Cognitive Science University of Athens (Prof. Fotini Stylianopoulou)
(Cognitive Neuroscience, Neural mechanisms of learning and memory)
2012-present Shervin Shafavi Master Thesis Student
2008-present Vishal Kapoor PhD student (MPI for Biological Cybernetics)
2011-2012 Shervin Shafavi, Sumit Pai, Manuel Alejandro Torres - Lab rotation students
2009-2011 Britni Crocker Master Thesis Student (now PhD student - MIT)
, and (September-2013) Desynchronization and rebound of beta oscillations during conscious and unconscious local neuronal processing in the macaque lateral prefrontal cortex Frontiers in Psychology 4(603) 1-10.
, , , and (May-2013) Development of Tube Tetrodes and a Multi-Tetrode Drive for deep structure electrophysiological recordings in the macaque brain Journal of Neuroscience Methods 216(1) 43–48.
, , and (January-2013) A Common Neurodynamical Mechanism Could Mediate Externally Induced and Intrinsically Generated Transitions in Visual Awareness PLoS ONE 8(1) 1-10.
, , and (September-2012) Introduction to research topic – binocular rivalry: a gateway to studying consciousness Frontiers in Human Neuroscience 6(263) 1-3.
, , and (June-2012) Neuronal Discharges and Gamma Oscillations Explicitly Reflect Visual Consciousness in the Lateral Prefrontal Cortex Neuron 74(5) 924–935.
, , , and (November-2011) Cortical microcircuit dynamics mediating binocular rivalry: the role of adaptation in inhibition Frontiers in Human Neuroscience 5(145) 1-19.
, , and (May-2011) 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 Neuroscience 181 89-99.
, , , and (May-2009) Visually Driven Activation in Macaque Areas V2 and V3 without Input from the Primary Visual Cortex PLoS ONE 4(5) 1-14.
, , , and (January-2009) Learning of a T-maze by rat pups when contact with the mother is either permitted or denied Neurobiology of Learning and Memory 91(1) 2-12.
, , , , , , , and (October-2008) Impairment of learning and memory in TAG-1 deficient mice associated with shorter CNS internodes and disrupted juxtaparanodes. Molecular and Cellular Neuroscience 39(3) 478-490.
, , , , , and (June-2008) Effect of neonatal handling on adult rat spatial learning and memory following acute stress Stress 11(2) 148-159.
, , , , and (September-2007) Anatomical landmarks: Dimensions of the mastoid air cell system in the Mediterranean population. Our experience from the anatomy of 298 temporal bones. Anatomical Science International 82(3) 139-146.
, , , , , and (April-2007) 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. Wound Repair and Regeneration 15(2) 252-257.
, , , , and (April-2005) Cellular mechanisms underlying the effects of an early experience on cognitive abilities and affective states. Ann Gen Psychiatry 4(1) 8-8.
, , , , , and (December-2004) Neonatal handling and gender modulate brain monoamines and plasma corticosterone levels following repeated stressors in adulthood. Neuroendocrinology 80(3) 181.
, , , , and (February-2004) Effect of neonatal handling and sex on basal and chronic stress-induced corticosterone and leptin secretion. Neuroendocrinology 79(2) 109.
, , , and (September-2013): Analyzing locking of spikes to spatio-temporal patterns in the macaque prefrontal cortex, Bernstein Conference 2013, Tübingen, Germany.
, , , , , and (February-2012): Identifying endogenous rhythmic spatio-temporal patterns in micro-electrode array recordings, 9th Annual Computational and Systems Neuroscience Meeting (Cosyne 2012), Salt Lake City, UT, USA.
, , , and (November-2011): Low frequency local field potentials in the inferior convexity of the macaque prefrontal cortex convey visual information during anesthesia, 41st Annual Meeting of the Society for Neuroscience (Neuroscience 2011), Washington, DC, USA.
, , , , , and (November-2011): Spatiotemporal mapping of rhythmic activity in the inferior convexity of the macaque prefrontal cortex, 41st Annual Meeting of the Society for Neuroscience (Neuroscience 2011), Washington, DC, USA.
, and (June-2010): Reduction of Correlated Noise in the Macaque Prefrontal Cortex during Conscious Visual Perception, AREADNE 2010: Research in Encoding And Decoding of Neural Ensembles, Santorini, Greece.
, , , and (November-2009): Comparing inter-ocular switch and classical binocular rivalry in the human brain using EEG, 10th Conference of Junior Neuroscientists of Tübingen (NeNa 2009), Ellwangen, Germany.
, , , and (October-2009): Comparing inter-ocular switch and classical binocular rivalry in the human brain using eeg, 39th Annual Meeting of the Society for Neuroscience (Neuroscience 2009), Chicago, IL, USA.
, , and (October-2009): Dynamical changes in functional circuitry of the macaque prefrontal cortex mediating a perceptual switch, 39th Annual Meeting of the Society for Neuroscience (Neuroscience 2009), Chicago, IL, USA.
, , , and (September-2009): High frequency local field potentials and multi unit activity reflect visual awareness in the macaque prefrontal cortex, 41st European Brain and Behaviour Society Meeting, Rhodos, Greece, Frontiers in Behavioral Neuroscience, Conference Abstract: 41st European Brain and Behaviour Society Meeting.
, , , and (July-2008): Neurophysiological substrates of visual awareness in the macaque prefrontal cortex, 6th Forum of European Neuroscience (FENS 2008), Geneva, Switzerland.
, , , and (June-2008): Single units reflect visual awareness in the macaque prefrontal cortex, AREADNE 2008: Research in Encoding and Decoding of Neural Ensembles, Santorini, Greece.
, and (October-2012) Abstract Talk: Beta oscillations propagate as traveling waves in the macaque prefrontal cortex, 42nd Annual Meeting of the Society for Neuroscience (Neuroscience 2012), New Orleans, LA, USA(413.03).
, , and (September-4-2008) Abstract Talk: On the neural mechanisms of binocular rivalry, 10th International Conference on Cognitive Neurosciences (ICON 2008), Bodrum, Turkey, Frontiers in Human Neuroscience, Conference Abstract: 10th International Conference on Cognitive Neuroscience.
, , , and (November-2007) Abstract Talk: Areas V2 and V3 remain active and retinotopically organized in the absence of direct V1 input, 37th Annual Meeting of the Society for Neuroscience (Neuroscience 2007), San Diego, CA, USA(122.2).