Author response: Minimally dependent activity subspaces for working memory and motor preparation in the lateral prefrontal cortex

The lateral prefrontal cortex is involved in the integration of multiple types of information, including working memory and motor preparation. However, it is not known how downstream regions can extract one type of information without interference from the others present in the network. Here, we show that the lateral prefrontal cortex of non-human primates contains two minimally dependent low-dimensional subspaces: one that encodes working memory information, and another that encodes motor preparation information. These subspaces capture all the information about the target in the delay periods, and the information in both subspaces is reduced in error trials. A single population of neurons with mixed selectivity forms both subspaces, but the information is kept largely independent from each other. A bump attractor model with divisive normalization replicates the properties of the neural data. These results provide new insights into neural processing in prefrontal regions.

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Independent Activity Subspaces for Working Memory and Motor Preparation in the Lateral Prefrontal Cortex

10.1101/756072 ◽

2019 ◽

Author(s):

Cheng Tang ◽

Roger Herikstad ◽

Aishwarya Parthasarathy ◽

Camilo Libedinsky ◽

Shih-Cheng Yen

Keyword(s):

Working Memory ◽

Prefrontal Cortex ◽

Motor Preparation ◽

Single Population ◽

Lateral Prefrontal Cortex ◽

Neural Data ◽

Divisive Normalization ◽

Attractor Model ◽

Low Dimensional ◽

Types Of Information

AbstractThe lateral prefrontal cortex is involved in the integration of multiple types of information, including working memory and motor preparation. However, it is not known how downstream regions can extract one type of information without interference from the others present in the network. Here we show that the lateral prefrontal cortex contains two independent low-dimensional subspaces: one that encodes working memory information, and another that encodes motor preparation information. These subspaces capture all the information about the target in the delay periods, and the information in both subspaces is reduced in error trials. A single population of neurons with mixed selectivity forms both subspaces, but the information is kept largely independent from each other. A bump attractor model with divisive normalization replicates the properties of the neural data. These results have implications for the neural mechanisms of cognitive flexibility and capacity limitations.

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Compressed Timeline of Recent Experience in Monkey Lateral Prefrontal Cortex

Journal of Cognitive Neuroscience ◽

10.1162/jocn_a_01273 ◽

2018 ◽

Vol 30 (7) ◽

pp. 935-950 ◽

Cited By ~ 26

Author(s):

Zoran Tiganj ◽

Jason A. Cromer ◽

Jefferson E. Roy ◽

Earl K. Miller ◽

Marc W. Howard

Keyword(s):

Working Memory ◽

Prefrontal Cortex ◽

Sample Stimulus ◽

Human Memory ◽

Recent Experience ◽

Lateral Prefrontal Cortex ◽

Elapsed Time ◽

Cognitive Theories ◽

Stimulus Identity ◽

Neural Underpinnings

Cognitive theories suggest that working memory maintains not only the identity of recently presented stimuli but also a sense of the elapsed time since the stimuli were presented. Previous studies of the neural underpinnings of working memory have focused on sustained firing, which can account for maintenance of the stimulus identity, but not for representation of the elapsed time. We analyzed single-unit recordings from the lateral prefrontal cortex of macaque monkeys during performance of a delayed match-to-category task. Each sample stimulus triggered a consistent sequence of neurons, with each neuron in the sequence firing during a circumscribed period. These sequences of neurons encoded both stimulus identity and elapsed time. The encoding of elapsed time became less precise as the sample stimulus receded into the past. These findings suggest that working memory includes a compressed timeline of what happened when, consistent with long-standing cognitive theories of human memory.

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