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Behavioral/Systems/Cognitive Human Posterior Parietal Cortex Plans Where to Reach

Summary: Behavioral/Systems/Cognitive
Human Posterior Parietal Cortex Plans Where to Reach
and What to Avoid
Axel Lindner, Asha Iyer, Igor Kagan, and Richard A. Andersen
California Institute of Technology, Division of Biology, Pasadena, California 91125
In this time-resolved functional magnetic resonance imaging (fMRI) study, we aimed to trace the neuronal correlates of covert
planning processes that precede visually guided motor behavior. Specifically, we asked whether human posterior parietal cortex
has prospective planning activity that can be distinguished from activity related to retrospective visual memory and attention.
Although various electrophysiological studies in monkeys have demonstrated such motor planning at the level of parietal neurons,
comparatively little support is provided by recent human imaging experiments. Rather, a majority of experiments highlights a role
of human posterior parietal cortex in visual working memory and attention. We thus sought to establish a clear separation of visual
memory and attention from processes related to the planning of goal-directed motor behaviors. To this end, we compared
delayed-response tasks with identical mnemonic and attentional demands but varying degrees of motor planning. Subjects
memorized multiple target locations, and in a random subset of trials targets additionally instructed (1) desired goals or (2)
undesired goals for upcoming finger reaches. Compared with the memory/attention-only conditions, both latter situations led to
a specific increase of preparatory fMRI activity in posterior parietal and dorsal premotor cortex. Thus, posterior parietal cortex has
prospective plans for upcoming behaviors while considering both types of targets relevant for action: those to be acquired and
those to be avoided.
Prospective plans of future action are initially represented in an


Source: Andersen, Richard - Division of Biology, California Institute of Technology
Crawford, Doug - York Centre for Vision Research, York University (Toronto)


Collections: Biology and Medicine