Oscillatory control over representational geometry of sequence working memory in macaque frontal cortex

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Computational Neuroscience

Background:

• The brain must encode sequential information, like language, using sequential working memory (SWM).
• Neural state geometry in the frontal cortex may represent sequential events, but control mechanisms are unclear.

Purpose of the Study:

• To investigate the neural control mechanisms underlying sequential working memory in the macaque frontal cortex.
• To determine how the brain encodes the ordinal relationship of sequentially presented items.

Main Methods:

• High-throughput electrophysiology recording of local field potential (LFP) and spike data in the macaque frontal cortex.
• Targeted dimensionality reduction to extract task-relevant neural subspaces.
• Analysis of theta responses and theta-spike interactions.

Main Results:

• Widespread theta responses were observed after each stimulus entry.
• Theta power transiently encoded individual stimuli irrespective of their order.
• Theta-spike interactions were selectively associated with memory subspaces, suggesting a role in rank-binding.

Conclusions:

• Decomposed entry/rank working memory (WM) subspaces and theta-spike interactions may control SWM.
• This theta control mechanism generalizes to variable-length and error-containing sequences, predicting behavior.