The Journal of Neuroscience, March 15, 2003, 23(6):2416
Cooperation between Area 17 Neuron Pairs Enhances Fine
Discrimination of Orientation
Jason M.
Samonds1,
John
D.
Allison2,
Heather A.
Brown1, and
A. B.
Bonds1, 2
Departments of 1 Biomedical and
2 Electrical Engineering, Vanderbilt University, Nashville,
Tennessee 37235
We examined 66 complex cells in area 17 of cats that were paralyzed
and anesthetized with propofol and N2O. We studied changes in ensemble responses for small (<10°) and large (>10°)
differences in orientation. Examination of temporal resolution and
discharge history revealed advantages in discrimination from both
dependent (e.g., synchronization) and independent (e.g., bursting)
interspike interval properties. For 27 pairs of neurons, we found that
the average cooperation (the advantage gained from the joint activity) was 57.6% for fine discrimination of orientation but <5% for gross discrimination. Dependency (probabilistic quantification of the interaction between the cells) was measured between 29 pairs of neurons
while varying orientation. On average, the dependency tuning for
orientation was 35.5% narrower than the average firing rate tuning.
The changes in dependency around the peak orientation (at which the
firing rate remains relatively constant) lead to substantial
cooperation that can improve discrimination in this region. The narrow
tuning of dependency and the cooperation provide evidence to support a
population-encoding scheme that is based on biologically plausible
mechanisms and that could account for hyperacuities.
Key words:
area 17; synchrony; coding; synergy; cooperation; orientation; discrimination
Copyright © 2003 Society for Neuroscience 0270-6474/03/2362416-10$05.00/0
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