Speaker/Affiliation: John Reynolds Ph.D. Associa

te Professor Systems Neurobiology Laboratory Salk Institute

When/L

ocation: 4/7/2008 12:00 PM SEA 4.244

Title of Talk: ''Mapping the

microcircuitry of attention: attentional modulation varies across cell clas

ses in visual area V4''

Reception with Refreshments at 11:30 AM
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br>Abstract: Cortical neurons differ from one another in important ways in

cluding their neurochemical properties patterns of connectivity laminar d

istribution gene expression patterns and developmental origin. Previous st

udies of attention have not sought to distinguish among different classes o

f neurons. We therefore know almost nothing about the complex circuitry tha

t transforms attentional feedback signals into improved visual processing.
Studies in the slice and in anesthetized animals find that parvalbumin exp

ressing GABA-ergic interneurons with the morphologies of basket and chandel

ier cells have short duration action potentials whereas most excitatory ce

ll classes have longer duration action potentials a difference that is due
to expression of different classes of sodium and potassium channels. We th

us examined differences in attentional modulation across visual area V4 neu

rons classified on the basis of action potential width. The distribution o

f action potential widths in area V4 is clearly bimodal. We find substanti

al differences in the basic response properties of these two classes of neu

rons including their baseline firing rates the strength of their stimulus

-evoked responses as well as qualitative differences in the types of varia

bility of the neuronal response across classes. We also find qualitative d

ifferences in how the two neuronal classes are modulated by attention incl

uding differences in how attention modulates firing rate and differences in
the attention-dependent reduction in response variability among the two cl

asses of neurons. The discovery differences in attentional modulation of f

iring rate and neuronal noise represents a key step forward in developing c

ircuit-level models of attention and visual processing.