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CNTRICS April 2010

CNTRICS April 2010. Center-surround: Adaptation to context in perception. Robert Shapley Center for Neural Science New York University. Perceptual adaptation --what it may tell us about cortical circuitry in schizophrenia. Adaptation is a fundamental aspect of brain activity

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CNTRICS April 2010

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  1. CNTRICS April 2010 Center-surround: Adaptation to context in perception Robert Shapley Center for Neural Science New York University

  2. Perceptual adaptation --what it may tell us about cortical circuitry in schizophrenia • Adaptation is a fundamental aspect of brain activity • Center-surround interaction is a kind of adaptation • Behavioral evidence for center-surround malfunction in schizophrenic patients • Mechanisms suggested by primate neurophysiology • Local Field Potential (LFP) power in the gamma band • Gamma and center-surround mechanisms • Implications of gamma abnormalities

  3. Center-surround perceptual effects and schizophrenia Dakin et al Current Biology 2005

  4. Adaptation: a fundamental aspect of brain activity “We conclude, therefore, that sense organs are not rigid machines but living and variable systems, the functioning of which is subject to variation. If a sensory system is exposed to a new and prolonged stimulus situation that departs from the one normally experienced, the system can be expected to undergo a fundamental change in its normal mode of operation.” (Ivo Kohler, 1962)--[my underlining]

  5. V1 cortex in monkey and human

  6. Intracolumnar feedforward and feedback connections (Sincich & Horton) Note LOOPS!

  7. Size tuning in V1 receptive fields:evidence for center-surround

  8. Cortical receptive field as a difference of gaussians Suppression index SI= Kib2/Kea2

  9. There is a lot of surround inhibition in V1(SI=inh/exc)maximal in layer 4B

  10. Collinear and Orthogonal Suppression: collinear much stronger because of tuned suppression

  11. Local Field Potential (LFP)fluctuations and center-surround interaction The Local Field Potential reflects the activity of many neurons in the local region around the electrode. Peaks in the power spectrum of the LFP may be clues to the properties of the cortical network (and its malfunctions). In V1 cortex the gamma band, defined as the band 25-90 Hz, is very useful.

  12. V1 cortex--responses to drifting grating patterns

  13. Gamma band peaks evoked by visual stimulation in V1

  14. Gamma Band peaks in LFP spectrum grow with stimulus size

  15. Cortical resonance model of gamma-band peaks (Kang, Shapley, Henrie, Shelley, 2009)

  16. Implications of gamma abnormalities in schizophrenia Change in E/I balance in the local circuit Hypothesis --reduced local circuit inhibition caused by something wrong in GABA inhibitory neurons or synapses Consistent with NMDA-->GABA malfunction leading to weakened GABA signal

  17. Similarities to the ideas in the Lisman hippocampus model from Lisman et al (2005) TINS 31, 234-242

  18. Perceptual adaptation --what it may tell us about cortical circuitry in schizophrenia • Adaptation is a fundamental aspect of brain activity • Center-surround interaction is a kind of adaptation • Behavioral evidence for center-surround malfunction in schizophrenic patients • Mechanisms suggested by primate neurophysiology • Local Field Potential (LFP) power in the gamma band • Gamma and center-surround mechanisms • Implications of gamma abnormalities

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