Contact

Dr. Vishal Kapoor

Address: Spemannstr. 38
72076 Tübingen
Room number: 230
Phone: +49 7071 601 697
Fax: +49 7071 601 652
E-Mail: vishal.kapoor

 

Picture of Kapoor, Vishal, Dr.

Vishal Kapoor

Position: Postdoctoral Fellow  Unit: Logothetis

Project 1:


Examination of functional interactions between prefrontal and inferotemporal cortex during binocular rivalry

Vishal Kapoor

 

Introduction and Aims

The brain has a remarkable way to resolve the conflict that arises when disparate visual stimuli are presented to corresponding retinal locations. It undergoes stochastic perceptual transitions, wherein only one of the stimuli attains conscious awareness. This phenomenon, which dissociates sensory stimulation from perception is called binocular rivalry (BR) and has been exploited extensively to study the neural correlates of visual awareness [1]. Neurophysiological experiments with non human primates trained to report their percept during BR have demonstrated that the percentage of cells correlated the animal’s perceptual report increase down the ventral visual pathway [2]. In the inferotemporal cortex (IT), 90 percent of the visually selective cells fire in concurrence with the reported visual percept [3]. Interestingly, ventrolateral prefrontal cortex (VLPFC), which has reciprocal anatomical connections with IT, shows increased BOLD activity in human subjects undergoing rivalry specifically during perceptual switches [4]. Furthermore, work in our lab has shown the existence of cells whose activity changes in accordance with the visual percept in the VLPFC of macaque monkey [5]. However, a mechanistic understanding of how these two areas interact with each other during alternations in perception remains unknown. The aim of this study is to explore with electrophysiology in non human primates, the functional interactions between IT and VLPFC, during a. spontaneous perceptual switches and b. stimulus suppression and dominance during BR. We illustrate below the first steps taken towards this direction, namely training of rhesus macaques in a visual discrimination task.

 

Methods

We have trained two rhesus macaques in a visual categorization task, wherein they discriminate stimuli alternating between three different categories which are presented to them with the help of a stereoscope. The animals maintain stable fixation in a +/-1.5 degree window for up to 25-30 seconds in a row, while reporting their percept by holding a lever pulled in response to two different categories of stimuli, namely a face and checkerboard pattern. They have been additionally trained not to pull a lever or release an already pulled lever when a physical mixture of the two stimuli, mimicking piecemeal perception, is presented.

 

Results and Conclusions

The animals perform the categorization task with good accuracy. One animal has reached the desired discrimination accuracy of ~95%, while the other has an accuracy of ~80% across sessions. Recently, the animal with higher accuracy has been exposed to single periods of binocular rivalry intermingled between periods of physical alternation. Preliminary observations show that the animal pulls levers to report his percept in a fashion similar to physical alternation. We are now in the process of standardizing stimulus parameters in order to optimize dominance and suppression times suitable for data collection. The next step is to examine their psychophysical behavior, when presented with rivalrous stimuli, and to verify that it complies with temporal parameters that are characteristic of binocular rivalry.

 

Collaborator

Theofanis Panagiotaropoulos

 

References

  1. Blake, R., N.K. Logothetis: Visual Competition. Nature Reviews Neuroscience, 3(1), 13-21 (2002).
  2. Logothetis, N.K.: Single units and conscious vision. Philosophical Transactions of Royal Society London, 353(1377), 1801-1818(1998).
  3. Sheinberg, D.L., N.K. Logothetis: The role of temporal cortical areas in perceptual organization. Proc. Natl. Acad. Sci. USA, 94(7), 3408-3413(1997).
  4. Lumer, E.D., K.J. Friston, G. Rees: Neural correlates of perceptual rivalry in the human brain. Science, 280(5371), 1930-1934(1998).
  5. Panagiotaropoulos T., V. Kapoor, G.A. Keliris, A. Tolias, N.K. Logothetis (2008): Neurophysiological substrates of visual awareness in the macaque prefrontal cortex, FENS Abstracts, 4, 220(2008).

 

Figure 1.

 

 

A. Exemplar stimuli on which the animals have been trained. B. The accuracy of discrimination of the two animals under training, G07 and F06.

 

 

Project 2:

 

Development of a Multi-Tetrode Drive for deep structure electrophysiological recordings in the macaque brain

 

Introduction and Aims

Understanding the principles that underlie information processing by neuronal networks requires simultaneous recordings from large populations of single units. Twisted wire tetrodes(TWTs), typically made by wounding four very thin wires (diameter – 12 microns) together, are ideally suited for such population recordings. They are advantageous over single electrodes; both with respect to reliability as well as the number of single units isolated [1,2] and have therefore been used extensively for superficial cortical recordings. However, their limited tensile strength poses a restriction to their use for recordings in deep brain areas. To our knowledge, TWTs have never been used for acute recordings in deep brain structures. We therefore developed a method to overcome this limitation in order to utilize tetrodes for electrophysiological recordings in the inferotemporal cortex (IT) of rhesus macaque. Our aim is to develop a) a method for making tetrodes stiffer and b) a multi-tetrode driving system for advancing them through a ball and socket chamber to precise locations for electrophysiological investigation of IT in the non human primate brain.

 

Methods

A mechanical technique has been developed for pulling regular TWTs inside 30 mm long stainless steel tubes (outer diameter - ~120 microns, inner diameter - ~50 microns) thus giving them rigidity. After this, the tetrode tip is glued and grinded and these new ‘tube tetrodes’ (TuTs) are inserted inside a 30 Gauge stainless steel holding tube. The impedance is then reduced by gold electroplating. Finally, they shall be positioned in the multi-tetrode recording drive which is being custom built for holding and independently moving, upto 5 TuTs through a ball and socket chamber.

 

Results and Conclusions

Initial test recordings made with our TuTs in the prefrontal cortex of an awake macaque reveals that they yield good cluster isolation similar to conventional TWTs. Further, we have implanted one animal with a ball and socket chamber for testing the multi-tetrode driving system. To conclude, we developed special TuTs which are stiffer as compared to TWTs, and have signal quality comparable to them. They are now ready to be integrated in the multi-tetrode driving system for further testing and performing electrophysiological recordings in the inferotemporal cortex.

 

Scientific Collaborator

Theofanis Panagiotaropoulos

 

Technical Collaborators

Eduard Krampe, Axel Klug

 

References

  1. Gray, M.C., P.E. Maldonado, M. Wilson, B. McNaughton: Tetrodes markedly improve the reliability and yield of single-unit isolation from multi-unit recordings in cat striate cortex. Journal of Neuroscience Methods, 63, 43-54(1995).
  2. Tolias AS, Ecker AS, Siapas AG, Hoenselaar A, Keliris GA, Logothetis NK. Recording chronically from the same neurons in awake, behaving primates. J Neurophysiol. 2007 98(6):3780-90.

 

Figure 2.



 

A. Schematic drawing showing the multi-tetrode drive placed on top of a ball and socket chamber sitting on top of the brain. The skull has been removed for demonstration purposes.  B.  Tube tetrode is shown looking out from the implanted guide tube of the ball and socket chamber. Notice the location of the tetrode above the IT cortex C. Micrograph of the Tube tetrode with four contacts embedded in glue. D. Screenshot taken during electrophysiological recording with a Tube tetrode.  On top, are the waveforms recorded on each of the four tetrode channels.  Below is shown online sorting of the signals by plotting /clustering the peak to peak amplitude of each waveform from different channels of the tetrode.


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Show abstracts

Articles (10):

Safavi S, Dwarakanath A, Kapoor V, Werner J, Hatsopoulos NG, Logothetis NK and Panagiotaropoulos TI (May-2017) Non-monotonic spatial structure of interneuronal correlations in prefrontal microcircuits - . in press
Safavi S, Kapoor V, Logothetis NK and Panagiotaropoulos TI (September-2014) Is the frontal lobe involved in conscious perception? Frontiers in Psychology 5(1063) 1-2.
Panagiotaropoulos TI, Kapoor V and Logothetis NK (March-2014) Subjective visual perception: From local processing to emergent phenomena of brain activity Philosophical Transactions of the Royal Society London B 369(1641) 1-13.
Panagiotaropoulos TI, Kapoor V and Logothetis NK (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.
Kapoor V, Krampe E, Klug A, Logothetis NK and Panagiotaropoulos TI (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.
Panagiotaropoulos TI, Kapoor V, Logothetis NK and Deco G (January-2013) A Common Neurodynamical Mechanism Could Mediate Externally Induced and Intrinsically Generated Transitions in Visual Awareness PLoS ONE 8(1) 1-10.
Panagiotaropoulos TI, Deco G, Kapoor V and Logothetis NK (June-2012) Neuronal Discharges and Gamma Oscillations Explicitly Reflect Visual Consciousness in the Lateral Prefrontal Cortex Neuron 74(5) 924–935.
Theodoni P, Panagiotaropoulos TI, Kapoor V, Logothetis NK and Deco G (November-2011) Cortical microcircuit dynamics mediating binocular rivalry: the role of adaptation in inhibition Frontiers in Human Neuroscience 5(145) 1-19.
Ray S, Bhutani N, Kapoor V and Murthy A (November-2011) Trans-saccadic processing of visual and motor planning during sequential eye movements Experimental Brain Research 215(1) 13-25.
Kapoor V and Murthy A (January-2008) Covert inhibition potentiates online control in a double-step task Journal of Vision 8(1:20) 1-16.
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Posters (19):

Safavi S, Panagiotaropoulos T, Kapoor T, Logothetis NK and Besserve M (July-24-2017): Generalized phase locking analysis of electrophysiology data, ESI Systems Neuroscience Conference (ESI-SyNC 2017): Principles of Structural and Functional Connectivity, Frankfurt a.M., Germany.
Kapoor V, Besserve M, Logothetis NK and Panagiotaropoulos TI (June-2016): Sequential Neuronal Activity in the lateral Prefronta Cortex during the Task of Binocular Flash Suppression, AREADNE 2016: Research in Encoding And Decoding of Neural Ensembles, Santorini, Greece.
Antoniou R, Safavi S, Kapoor V, Logothetis NK and Panagiotaropoulos T (October-9-2015): Perceptual modulation of pupillary reflex in macaque monkeys, Federation of European Neuroscience Society Featured Regional Meeting (FFRM 2015), Thessaloniki, Greece.
Kapoor V, Besserve M, Logothetis NK and Panagiotaropoulos TI (September-19-2015): Single unit responses in the lateral prefrontal cortex reflect trial phase dependent modulation, 4th Champalimaud Neuroscience Symposium: Perspectives on Social Behavior, Lisboa, Portugal.
Kapoor V, Besserve M, Logothetis NK and Panagiotaropoulos TI (July-10-2015): Activity Patterns in the Lateral Prefrontal Cortex Reflect Trial Phase Dependent Response Modulations, 9th IBRO World Congress on Neuroscience (IBRO 2015), Rio de Janeiro, Brazil.
Safavi S, Panagiotaropoulos T, Kapoor V, Logothetis NK and Besserve M (November-12-2013): Coupling between spiking activity and beta band spatio-temporal patterns in the macaque PFC, 43rd Annual Meeting of the Society for Neuroscience (Neuroscience 2013), San Diego, CA, USA.
Safavi S, Panagiotaropoulos T, Kapoor V, Logothetis NK and Besserve M (September-2013): Analyzing locking of spikes to spatio-temporal patterns in the macaque prefrontal cortex, Bernstein Conference 2013, Tübingen, Germany.
Theodoni P, Panagiotaropoulos TI, Kapoor V, Logothetis NK and Deco G (June-2012): Cortical microcircuit dynamics in visual awareness, AREADNE 2012: Research in Encoding and Decoding of Neural Ensembles, Santorini, Greece.
Besserve M, Panagiotaropoulos T, Crocker B, Kapoor V, Tolias A, Panzeri S and Logothetis NK (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.
Crocker B, Kapoor V, Panzeri S, Logothetis NK and Panagiotaropoulos T (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.
Panagiotaropoulos T, Besserve M, Crocker B, Kapoor V, Tolias AS, Panzeri S and 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.
Panagiotaropoulos T, Kapoor V and Logothetis NK (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.
Kapoor V, Whittingstall K, Panagiotaropoulos T, Keliris G and Logothetis NK (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.
Kapoor V, Whittingstall K, Panagiotaropoulos T, Keliris GA and Logothetis NK (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.
Panagiotaropoulos T, Komlos M, Kapoor V and Logothetis NK (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.
Panagiotaropoulos T, Kapoor V, Keliris GA, Tolias A and Logothetis NK (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.
Panagiotaropoulos T, Kapoor V, Keliris GA, Tolias A and Logothetis NK (July-2008): Neurophysiological substrates of visual awareness in the macaque prefrontal cortex, 6th Forum of European Neuroscience (FENS 2008), Geneva, Switzerland.
Panagiotaropoulos T, Kapoor V, Keliris GA, Tolias A and Logothetis NK (June-2008): Single units reflect visual awareness in the macaque prefrontal cortex, AREADNE 2008: Research in Encoding and Decoding of Neural Ensembles, Santorini, Greece.
Murthy AN and Kapoor V (September-2007): Does covert inhibition potentiate online inhibitory control?, 30th Annual Meeting of the Japan Neuroscience Society (Neuro 2007), Yokohama, Japan, Neuroscience Research, 58(Supplement 1) S228.

Theses (1):

Kapoor V: Control of internally and externally guided actions, National Brain Research Centre, Manesar, India, (2006). PhD thesis

Talks (6):

Safavi S, Dwarakanath A, Besserve M, Kapoor V, Logothetis NK and Panagiotaropoulos TI (June-2016) Abstract Talk: A Non-Monotonic Correlation Structure in the Macaque Ventrolateral Prefrontal Cortex, AREADNE 2016: Research in Encoding And Decoding of Neural Ensembles, Santorini, Greece 53.
Dwarakanath A, Safavi S, Kapoor V, Logothetis NK and Panagiotaropoulos T (November-23-2015) Abstract Talk: Temporal Regimes of State-Dependent Correlated Variability in the Macaque Ventrolateral Prefrontal Cortex, 16th Conference of Junior Neuroscientists of Tübingen (NeNa 2015): Communicating the Challenges of Science, Schramberg, Germany 18.
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Kapoor V (October-31-2013) Abstract Talk: Development and use of tube tetrodes for electrophysiological investigation of deep lying brain structures of the macaque, Donders Discussions 2013, Nijmegen, The Netherlands 20.
Kapoor V (September-14-2013) Invited Lecture: Development and use of tube tetrodes for electrophysiological investigation of deep lying brain structures of the macaque, Networks! 2013: 4th German Neurophysiology PhD Meeting, Tübingen, Germany.
Kapoor V and Murthy A (November-26-2007) Abstract Talk: Does covert inhibition facilitate the dynamic control of decision making?, 8th Conference of Tuebingen Junior Neuroscientists (NeNa 2007), Freudenstadt, Germany 9.

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Last updated: Monday, 22.05.2017