Chance, F.S. & Abbott, L.F. (2005) Drivers and modulators from
push-pull and balanced synaptic input. Progress in Brain Research 149:
147-155.
Abstract
In 1998, Sherman and Guillery proposed that there are two types of
inputs to cortical neurons; drivers and modulators. These two forms of
input are required to explain how, for example, sensory driven
responses are controlled and modified by attention and other internally
generated gating signals. One might imagine that driver signals are
carried by fast ionotropic receptors, whereas modulators correspond to
slower metabotropic receptors. Instead, we have proposed a novel
mechanism by which both driver and modulator inputs could be carried by
transmission through the same types of ionotropic receptors. In this
scheme, the distinction between driver and modulator inputs is
functional and changeable rather than anatomical and fixed. Driver
inputs are carried by excitation and inhibition acting in a push-pull
manner. This means that increases in excitation are accompanied by
decreases in inhibition and vice versa. Modulators correspond to
excitation and inhibition that covary so that they increase or decrease
together. Theoretical and experimental work has shown that such an
arrangement modulates the gain of a neuron, rather than driving it to
respond. Constructing drivers and modulators in this manner allows
individual excitatory synaptic inputs to play either role, and indeed
to switch between roles, depending on how they are linked with
inhibition.
return