Synfire Chains and Cortical Songs: Temporal Modules of Cortical Activity

TLDR

The study investigates how neural activity propagates through cortical networks composed of weak, stochastic synapses. Calcium imaging of cortical slices revealed reactivation of cell sequences during repeated intracellular synaptic patterns. Spontaneous synaptic input patterns in neocortical neurons repeat with millisecond precision over minutes, drift over time engaging different cells, and form modular temporal dynamics that are replayed in the same order and compressed at higher orders.

Abstract

How can neural activity propagate through cortical networks built with weak, stochastic synapses? We find precise repetitions of spontaneous patterns of synaptic inputs in neocortical neurons in vivo and in vitro. These patterns repeat after minutes, maintaining millisecond accuracy. Calcium imaging of slices reveals reactivation of sequences of cells during the occurrence of repeated intracellular synaptic patterns. The spontaneous activity drifts with time, engaging different cells. Sequences of active neurons have distinct spatial structures and are repeated in the same order over tens of seconds, revealing modular temporal dynamics. Higher order sequences are replayed with compressed timing.