Cortical timing and activation patterns during spatial conditional motor learning

Eliassen JC, Baker JT, Sanes JN (1999)  Soc. Neurosci. Abstr., 567.17.

Neurophysiological studies have found neural activity changes in frontal cortex while monkeys learn to associate an arbitrary visual stimulus with a specific movement.  In humans, neuroimaging data indicate that application of an already learned rule between arbitrary visual cues and movements yields changed activation in frontal and parietal areas.  These neuroimaging studies have only addressed brain activation during rule application rather than rule formation.  By contrast, we designed an experiment to assess the within- and between-trial timing and activation patterns across cortex during rule formation and application.

Yound adult humans learned to associate, using trial and error, one of six visual cues with a right-handed button press using digits 2-5 during event-related functional MRI.  The visual cues appeared at one of six locations evenly spaced around a virtual circle.  Participants performed 72 trials (20 sec each), and they typically learned the visual -motor associations in the first half of the trials.  BOLD EPI functional MR signals were collected from 5 axial oriented slices from the superior convexity to the corpus callosum.  Activated voxels were identified with correlation methods.

During early and late learning, task-related activation was present in severeal areas, including supplementary motor area, primary motor cortex, premotor area, prefrontal cortex, intraparietal sulcus, and a parietal area near the parieto-occipital junction (POJ).  To date, we found that the POJ exhibited greater areal activation in the latter compared to the earlier learning phases.  The other areas exhibited comparable areal activation across the two task phases.  These data are consistent with a role for the posterior parietal cortex in spatial visual motor transformations.