Abstract
The notion of gating as a mechanism capable of controlling the flow of information from one set of neurons to another, has been studied in many regions of the central nervous system. In the nucleus accumbens, where evidence is especially clear, gating seems to rely on the action of bistable neurons, i.e., of neurons that oscillate between a quiescent “down” state and a firing “up” state, and that act as AND-gates relative to their entries. Independently from these observations, a growing body of evidence now indicates that bistable neurons are also quite abundant in the cortex, although their exact functions in the dynamics of the brain remain to be determined. Here, we propose that at least some of these bistable cortical neurons are part of circuits devoted to gating information flow within the cortex. We also suggest that currently available structural, electrophysiological, and imaging data support the existence of at least three different types of gating architectures. The first architecture involves gating directly by the cortex itself. The second architecture features circuits spanning the cortex and the thalamus. The third architecture extends itself through the cortex, the basal ganglia, and the thalamus. These propositions highlight the variety of mechanisms that could regulate the passage of action potentials between cortical neurons sets. They also suggest that gating mechanisms require larger-scale neural circuitry to control the state of the gates themselves, in order to fit in the overall wiring of the brain and complement its dynamics.
Highlights
The concept of gating in the cortex, i.e., of mechanisms that are capable of interrupting, or allowing, the passage of action potentials between distinct sets of cortical neurons, is rapidly generating increasing amounts of interest.This interest is probably largely motivated by the growing number of electrophysiological and magnetic resonance imaging studies bringing support to the idea of gating
It was later shown by Sakai et al (2002), using a magnetic resonance imaging experimental setup requiring that subjects keep in mind information while performing a non-related distractor task, that area 46 of the prefrontal cortex seems able to implement a type of shielding mechanism allowing different information to be simultaneously kept in mind
Alternate Gating Architectures A mechanism gating the access to working memory involving the basal ganglia, but differing from that presented above (Figure 9), has been proposed by the group of Frank and O’Reilly (Frank et al, 2001)
Summary
In the nucleus accumbens, where evidence is especially clear, gating seems to rely on the action of bistable neurons, i.e., of neurons that oscillate between a quiescent “down” state and a firing “up” state, and that act as AND-gates relative to their entries. The third architecture extends itself through the cortex, the basal ganglia, and the thalamus These propositions highlight the variety of mechanisms that could regulate the passage of action potentials between cortical neurons sets. They suggest that gating mechanisms require larger-scale neural circuitry to control the state of the gates themselves, in order to fit in the overall wiring of the brain and complement its dynamics
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