5.7: Executive Function- Prefrontal Cortex and Basal Ganglia
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Finally, we build upon the motor control functions of frontal cortex and basal ganglia to understand how these two areas interact to support high-level executive function.
We also build upon the functional divisions of the posterior cortex to understand how the ventral vs. dorsal areas of prefrontal cortex are functionally organized. Figure 5.10 shows an overall schematic for how this occurs. It also illustrates how the lateral surface is more associated with "cold" cognitive function, while the medial surface is more involved in "hot" emotional and motivational processing.
We'll see how the PFC can provide top-down cognitive control over processing in the posterior cortex, with the classic example being the Stroop task.
Then we'll explore how PFC and BG can interact to produce a dynamically gated working memory system that allows the system to hold multiple pieces of information 'in mind', and to separately update some pieces of information while continuing to maintain some existing information. The role of the BG in this system builds on the more established role of the BG in motor control, by interacting in very similar circuits with PFC instead of motor cortex. In both cases, the BG provide a gating signal for determining whether or not a given frontal cortical 'action' should be executed or not. It's just that PFC actions are more cognitive than motor cortex, and include things like updating of working memory states, or of goals, plans, etc. Once updated, these PFC representations can then provide that top-down cognitive control mentioned above, and hence can shape action selection in BG-motor circuits, but also influence attention to task-relevant features in sensory cortex. Interestingly, the mechanisms for reinforcing which cognitive actions to execute (including whether or not to update working memory, or to attend to particular features, or to initiate a high level plan) seem to depend on very similar dopaminergic reinforcement learning mechanisms that are so central to motor control. This framework also provides a link between motivation and cognition which is very similar to the well established link between motivation and action.