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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
• 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
Center-surround perceptual effects and
schizophrenia
QuickTime™ and a
decompressor
are needed to see this picture.
Dakin et al Current Biology 2005
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]
V1 cortex in monkey and human
Intracolumnar feedforward and feedback connections
(Sincich & Horton) Note LOOPS!
QuickTime™ and a
decompressor
are needed to see this picture.
Size tuning in V1 receptive fields:
evidence for center-surround
Cortical receptive field as a difference of
gaussians
Suppression index
SI= Kib2/Kea2
QuickTime™ and a
BMP decompressor
are needed to see this picture.
There is a lot of
surround inhibition
in V1(SI=inh/exc)
maximal in layer
4B
Collinear and Orthogonal Suppression: collinear
much stronger because of tuned suppression
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.
V1 cortex--responses to drifting grating patterns
Gamma band peaks evoked by visual stimulation in V1
Gamma Band peaks in LFP spectrum grow with stimulus size
Cortical resonance model of gamma-band peaks
(Kang, Shapley, Henrie, Shelley, 2009)
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
Similarities to the ideas in the Lisman hippocampus model
from Lisman et al (2005) TINS 31, 234-242
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