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- L. Schwabe, K. Obermayer,
A. Angelucci, and P. Bressloff. The Role of Feedback in Shaping the
Extra-Classical Receptive Field of Cortical Neurons: A Recurrent Network
Model.
.
J. Neurosci., 26:9117-9129, 2006.
The article on The
Journal of Neuroscience website. © The Society for Neuroscience.
(FTP PDF, 520 kb)
The responses of neurons in sensory cortices are affected by the
spatial context within which stimuli are embedded. In the primary visual
cortex (V1), orientation-selective responses to stimuli in the receptive
field (RF) center are suppressed by similarly oriented stimuli in the RF
surround. Surround suppression, a likely neural correlate of perceptual
figure-ground segregation, is traditionally thought to be generated within V1
by long-range horizontal connections. Recently however, it has been shown
that these connections are too short and too slow to mediate fast suppression
from distant regions of the RF surround. We use an anatomically and
physiologically constrained recurrent network model of macaque V1 to show how
interareal feedback connections, which are faster and longer-range than
horizontal connections, can generate "far" surround suppression. We
provide a novel solution to the puzzle of how surround suppression can arise
from excitatory feedback axons contacting predominantly excitatory neurons in
V1. The basic mechanism involves divergent feedback connections from the far
surround targeting pyramidal neurons sending monosynaptic horizontal
connections to excitatory and inhibitory neurons in the RF center. One of
several predictions of our model is that the "suppressive far
surround" is not always suppressive, but can facilitate the response of
the RF center, depending on the amount of excitatory drive to the local
inhibitors. Our model provides a general mechanism of how top-down feedback
signals directly contribute to generating cortical neuron responses to simple
sensory stimuli.
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