Abstract For:
Chance, F.S., Abbott, L.F. & Reyes, A.D. (2002) Gain Modulation from
Background Synaptic Input. Neuron 35: 773-782.
Gain modulation is a prominent feature of neuronal activity recorded in
behaving animals, but the mechanism by which it occurs is unknown. By introducing
a barrage of excitatory and inhibitory synaptic conductances that mimics conditions
encountered in vivo into pyramidal neurons in slices of rat somatosensory
cortex, we show that the gain of a neuronal response to excitatory drive can
be modulated by varying the level of "background" synaptic input. Simultaneously
increasing both excitatory and inhibitory background firing rates in a balanced
manner results in a divisive gain modulation of the neuronal response without
appreciable signal-independent increases in firing rate or spike-train variability.
These results suggest that, within active cortical circuits, the overall
level of synaptic input to a neuron acts as a gain control signal that modulates
responsiveness to excitatory drive.
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