On the actions that one nerve cell can have on another: Distinguishing “drivers” from “modulators”

Abstract

When one nerve cell acts on another, its postsynaptic effect can vary greatly. In sensory systems, inputs from ''drivers'' can be differentiated from those of ''modulators.'' The driver can be identified as the transmitter of receptive field properties; the modulator can be identified as altering the probability of certain aspects of that transmission. Where receptive fields are not available, the distinction is more difficult and currently is undefined. We use the visual pathways, particularly the thalamic geniculate relay for which much relevant evidence is available, to explore ways in which drivers can be distinguished from modulators. The extent to which the distinction may apply first to other parts of the thalamus and then, possibly, to other parts of the brain is considered. We suggest the following distinctions: Crosscorrelograms from driver inputs have sharper peaks than those from modulators; there are likely to be few drivers but many modulators for any one cell; and drivers are likely to act only through ionotropic receptors having a fast postsynaptic effect whereas modulators also are likely to activate metabotropic receptors having a slow and prolonged postsynaptic effect.

Learning and inference in the brain

“…The asymmetry between forward and backward connections maps nicely onto the distinction between driving and modulatory effects proposed by Sherman and Guillery (1998). (i) Cross-correlograms from driving inputs have sharper peaks than modulatory inputs, (ii) there are likely to be few drivers but many modulators for any cell, and (iii) drivers act through (fast) ionotropic receptors, whereas modulators also activate metabotropic receptors with a slow and prolonged post-synaptic effect.…”

“…At the single cell level "inputs from drivers can be differentiated from those of modulators. The driver can be identified as the transmitter of receptive field properties; the modulator can be identified as altering the probability of certain aspects of that transmission" (Sherman & Guillery, 1998).…”

Free-energy and the brain

“…Due to convergence and divergence of extrinsic forward and backward connections, receptive fields in higher areas are generally larger than in lower areas (Zeki and Shipp 1988). There is a key functional distinction between forward and backward connections that renders backward connections more modulatory or non-linear in their effects on neuronal responses (e.g., Sherman and Guillery 1998). This is consistent with the deployment of voltage sensitive and non-linear NMDA receptors in the supra-granular layers (Rosier et al 1993) that are targeted by backward connections.…”

Circuits for Multisensory Integration and Attentional Modulation Through the Prefrontal Cortex and the Thalamic Reticular Nucleus in Primates

“…Pathways from the thalamus that terminate extensively in the superficial cortical layers, or the prevalent cortical projections form layer VI to the thalamus, are considered to be modulatory pathways. Some studies have provided evidence that driver pathways, at least in the thalamus, have large terminals, whereas modulatory pathways have small terminals / 1,68,72,86,87,88,96,104,113,138,139,151,153 /.…”