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| Dynamics and Plasticity in Adult Cortex |
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| Synaptic integration in the visual cortex |
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The
Sur lab studies cortical networks, which take simple inputs and
make complex outputs. In the visual cortex, these outputs are manifested
as selective responses to specific visual features. These features
are mapped systematically across the cortex - we have shown that
feature maps in V1 share important relationships with each other
to account for continuity of representation and coverage of the
visual field. The maps in turn influence the way response selectivity
is generated: by recording intracellularly from neurons that lie
in different locations within the map of orientation preference,
we have demonstrated that orientation selectivity requires a balance
of excitation and inhibition. The tuning of excitatory and inhibitory
conductances varies from pinwheel centers to orientation domains,
but the exquisite balance between the two ensures that spike outputs
are sharply tuned for orientation at all locations. We are now
using molecular genetic and calcium imaging tools, combined with
two-photon and intrinsic signal imaging, to examine the mechanisms
by which visual cortex neurons and networks process and represent
information.
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Beata Jarosiewicz
Caroline Runyan
James Schummers
Hongbo Yu
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| Bottom up and top down dynamics in the visual cortex |
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Cortical processing of sensory information integrates not only bottom up inputs from the sensory surface but also top down
information about internal state, including attention, expectation and memory. We propose that top down 'learning' signals
modulate responses in early cortical areas in accord with predictions about bottom up inputs. Thus, we have shown that
orientation-specific responses of V1 neurons in alert monkeys can be modulated according to Bayesian estimates of stimulus
location. Using multiple electrode recording and optical imaging in alert monkeys combined with computational models, we are
now examining other predictive top down influences, including those due to location based attention and feature based
expectation.
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Scott Gorlin
Jitendra Sharma
Hiroki Sugihara
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| Influence of electrical activity on cortical networks in vivo |
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Specific rules underlie the generation and maintenance of cortical networks. These include principles of balanced excitation and inhibition, homeostasis or regulation of total drive, and synaptic plasticity based on patterns of input and output activity. We are examining several of these rules in isolation or in combination. The experiments utilize novel materials and technologies to grow networks in vitro, in which we can control the size, neuronal density, linkage, or the efficacy of synaptic connections.
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Nathan Wilson
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| > adult
cortex projects |
| > research overview |
