SENSORIMOTOR TRANSFORMATIONS IN CORTICAL MOTOR AREAS

本研究的目的是了解皮质运动场是如何

The goal of this research is to learn how the cortical motor fields (CMFs) use exteroceptive and contextual information in the selection and planning of visually instructed limb movements. Studies of neuronal activity in cortical motor areas suggest the orderly recruitment of sensory-related, followed by associative, followed by motor-related activity during such behaviors. These and other observations suggest a model of the CMFs in which sensory-to-motor transformations (SMTs) required for visual instructed limb movements are distributed both in time, within each motor field, and in space, across the network of CMFs. Among the model's predictions are early recruitment of CMFs engaged in sensory and associative processing of visual information, and later recruitment of areas whose processing is more strictly motor. This proposal has 4 specific aims: SA1: To test the hypothesis that for spatial SMTs in which the location of a visual stimulus (IS) instructs a targeted limb movements instructed there is a common sequence of neuronal recruitment (sensory-related-greater than-greater than motor- related activity) within each participating CMF. Neuronal activity will be sampled from motor cortex (MC), the dorsaal premotor area (PMd), and pre-PMd in monkeys performing tasks that dissociate sensory, associative, and motor-related processing. Multiple regression will be used in a continuous time course analysis to determine the proportions of each cell's activity attributable to the 3 types of processing. Population analyses will assess whether recruitment follows the predicted pattern within each region. SA2: To test the hypothesis that spatial SMTs entail a cascading sequence of neuronal recruitment distributed across the network of CMFs, with early recruitment of CMFs engaged in sensory processing, followed in turn by those specialized for associative and finally motor processing. Data collected from MC, PMd, and pre-PMd in SA1 will be compared across regions, to determine whether the pattern of neuronal recruitment distributed across the network of CMFs conforms to the model's predictions. SA3: To test the hypothesis that within each participating CMF the same sequence of neuronal recruitment predicted for spatial SMTs (SA1) holds for visual SMTs that are non-spatial. Neuronal activity will be sampled from MC, the supplementary motor area (SMA), and pre-SMA in monkeys performing non- targeted limb movements instructed by the colors and shapes (not locations) of visual stimuli. Data will be analyzed in the same manner as in SA1. SA4: To test the hypothesis that non-spatial SMTs entail a pattern of neuronal recruitment distributed across the network of CMFs comparable to that predicted for spatial SMTs (SA2). Data collected from MC, SMA, and pre-SMA in SA3 will be compared across CMFs to assess whether the pattern of recruitment distributed across the network conforms to the model's predictions.