Frontal and parietal networks for conditional motor learning: a positron emission tomography study

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Neuroimaging

Background:

• Nonhuman primate studies indicate premotor (PM) and prefrontal (PF) areas are crucial for arbitrary stimulus-response mapping.
• Previous human studies using positron emission tomography (PET) for regional cerebral blood flow (rCBF) have not consistently shown predicted brain activity changes during these tasks.

Purpose of the Study:

• To investigate regional cerebral blood flow (rCBF) changes in human subjects during the learning of arbitrary mapping tasks.
• To identify specific brain regions involved in processing arbitrary rules and their associated motor responses.

Main Methods:

• Positron emission tomography (PET) was used to measure regional cerebral blood flow (rCBF) in human subjects.
• Two arbitrary mapping tasks were employed: a conditional motor task and an evaluation task, each with nonspatial, spatial, and fixed-response rules.

Main Results:

• Learning the nonspatial rule in the evaluation task increased rCBF in the premotor cortex (PMvc), putamen, and cingulate motor area (CM), while decreasing it in the ventro-orbital prefrontal cortex (PFv), cerebellum, and posterior parietal cortex.
• The conditional motor task showed decreased rCBF in the parietal area.
• Learning the spatial rule in the conditional motor task decreased rCBF in the premotor cortex (PMvr), dorsolateral prefrontal cortex (PFdl), and posterior parietal cortex.

Conclusions:

• The study confirms predicted rCBF changes in premotor and prefrontal areas during arbitrary mapping tasks in humans.
• Findings suggest that a broad frontoparietal network exhibits reduced synaptic activity as arbitrary rules become more familiar.