Abstract
Neural activity in the brain traces sequential trajectories on low dimensional subspaces. For flexible behavior, these neural subspaces must be manipulated and reoriented within tens of milliseconds. Using mathematical analysis and simulation of a recurrently connected neural circuit for sequence generation, we report that incorporating a subtype of interneurons that provides sparse but clustered inhibition enables the projection of sequential activity onto task- or context-specific neural subspaces. Depending on the sparsity of inhibitory projections, neural subspaces could be arbitrarily rotated with respect to the intrinsic subspace, without altering the key aspects of sequence generation. Thus, we propose a circuit motif and mechanism by which inhibitory interneurons can enable flexible switching between neural subspaces on a fast timescale of milliseconds, controlled by top down signals.
Significance Statement
Significance Statement Cognitive faculties like memory, movement, and decision-making depend on the reliable sequential activation of neurons in the brain. These activity sequences reside on low dimensional neural subspaces, with different tasks or behaviors represented on different subspaces. Flexible cognition therefore requires changes in subspace orientation on timescales as fast as tens of milliseconds. Here we propose a mechanism for fast timescale control of the neural subspace in a recurrently connected neural network model for sequence generation. Subspace manipulation is implemented by inhibitory neurons that form sparse, clustered axonal projections onto the neurons responsible for sequence generation. Ensembles of these inhibitory neurons rapidly rotate the neural subspace and support storage of and dynamical switching between neural activity sequences on low dimensional manifolds.
Competing Interest Statement
The authors have declared no competing interest.