Hierarchically Organized Medial Frontal Cortex-Basal Ganglia Loops Selectively Control Task- and Response-Selection

Area of Science:

• Cognitive Neuroscience
• Neuroimaging
• Computational Modeling

Background:

• Adaptive behavior relies on context-sensitive task-sets, influencing stimulus-response mappings.
• Task-set and response-selection exhibit strong interaction, with switch costs varying based on repetition or switching.
• The neurocognitive basis for this interdependence between task- and response-level control remains unclear.

Purpose of the Study:

• To formalize and test a hierarchical model explaining the interaction between task-set and response-selection costs.
• To investigate the neural circuitry underlying these interactive control processes using functional magnetic resonance imaging (fMRI).
• To confirm the distinct roles of the presupplementary motor area (preSMA) and supplementary motor area (SMA) in response costs via transcranial magnetic stimulation (TMS).

Main Methods:

• Developed and validated a computational model of hierarchical task-set and response-set selection.
• Utilized fMRI in healthy participants to map brain activity correlated with task- and response-switch costs.
• Employed fMRI-guided TMS to probe the causal involvement of preSMA and SMA in cognitive control.

Main Results:

• The hierarchical model successfully predicted behavioral patterns of task- and response-switch costs.
• fMRI revealed distinct neural correlates: preSMA activity tracked task-set costs, SMA activity tracked response-set costs, and basal ganglia activity reflected their interaction.
• TMS experiments demonstrated dissociable functions of preSMA and SMA in modulating response costs.

Conclusions:

• Evidence supports a hierarchical organization within the posterior medial frontal cortex and basal ganglia for cognitive control.
• A superordinate preSMA-basal ganglia loop governs task-set selection, imposing constraints on a subordinate SMA-basal ganglia loop responsible for response selection.
• This hierarchical structure explains the observed interdependence in behavioral task- and response-switch costs, providing a neural basis for cognitive flexibility.