Summary

Flexible recruitment of memory-based choice representations by the human medial frontal cortex

09 Apr 2021 - Meng Wang

Report Summary:

We could extract different aspects of information from the same object for different purpose, especially when making decisions. How is this cognitive flexibility implemented in brain? This paper approaches this big question by investigating how medial frontal cortex (MFC) selectively represents current task-related information and particularly, how MFC even retrieves the current task-related memory from hippocampus and amygdala (HA).

More specifically, this paper focuses on two tasks: patients are instructed to make binary (yes/no) decision based on the same image but for different purpose: “is this image a fruit?” (categorization task) or “have you seen this image before?” (memory task). The recorded single-unit spiking activity is used to decode five variables: task type (categorization/memory), response modality(button press/saccade), category(human face/monkey face/fruit/..), memory(new/old), choice(yes/no) to quantify the strength of representation of these behavior variables in MFC and HA, and importantly, the cross-decoding of the other four variables between two different task types to measure how the same behavioral variable is distinctively encoded to fullfill current task needs in a geometrical view.

They found that: (1) MFC predominantly represents task type and choice (90% decoding accuracy), not varying with task types. And the geometry of the representation for choice is different under two task types. (2) Image category and familiarity is differently encoded in MFC under two tasks while HA not, in terms of both the strength and geometry. (3) Response type is similarly represented in MFC but not HA under two task types. (4) MFC cell-HA LFP theta and gamma coherence is stronger under memory task than categorization task.

The result collectively demonstrates that MFC could selectively represent task-related information and even retrieve past memory for current task from other brain areas, instead of blindly encoding sensory/behavior information, indicating that task type distinctively configure MFC to represent and retrieve other more specific information. The future main question would be how the task type is formed in prefrontal cortex and configures the MFC. Do they involve different groups of neurons or same groups of neuron but in different dynamics?

Original author： Meng Wang
Link： https://CNeuroUSTC.github.io/2021/04/09/MengWang.html
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