| Abstract: | How is spatial information for limb movement encoded in thebrain? Computational and psychophysical studies suggest thatbeginning hand position, via-points, and target are specifiedrelative to the body to afford a comparison between the sensory(e. g., kinesthetic) reaf-ferences and the commands that generatelimb movement Here we propose that the superior parietal lobule(Brodmann area 5) might represent a substrata for a body-centeredpositional code. Monkeys made arm movements in different partsof 3D space in a reaction-time task. We found that the activityof area 5 neurons can be related to either the starting pointor the final point or combinations of the two. Neural activityis monotonicalty tuned in a body-centered frame of reference,whose coordinates define the azimuth, elevation, and distanceof the hand. Each spatial coordinate tends to be encoded ina different sub-population of neurons. This parcellation couldbe a neural correlate of the psychophysical observation thatthese spatial parameters are processed in parallel and largelyindependent of each other in man. |
