Synaptic Depression and Cortical Gain Control
L. F. Abbott,
*
J. A. Varela,
Kamal Sen,
S. B. Nelson
Cortical neurons receive synaptic inputs from thousands of
afferents that fire action potentials at rates ranging from less than 1 hertz to more than 200 hertz. Both the number of afferents and their
large dynamic range can mask changes in the spatial and temporal
pattern of synaptic activity, limiting the ability of a cortical neuron
to respond to its inputs. Modeling work based on experimental
measurements indicates that short-term depression of intracortical
synapses provides a dynamic gain-control mechanism that allows equal
percentage rate changes on rapidly and slowly firing afferents to
produce equal postsynaptic responses. Unlike inhibitory and adaptive
mechanisms that reduce responsiveness to all inputs, synaptic
depression is input-specific, leading to a dramatic increase in the
sensitivity of a neuron to subtle changes in the firing patterns of its
afferents.
L. F. Abbott and Kamal Sen, Volen Center, Brandeis University,
Waltham, MA 02254, USA.
J. A. Varela and S. B. Nelson, Department of Biology, Brandeis
University, Waltham, MA 02254, USA.
*
To whom correspondence should be addressed.
