Representing spatial information for limb movement: role of area 5 in the monkey.
How is spatial information for limb movement encoded in the brain? Computational and psychophysical studies suggest that beginning hand position, via-points, and target are specified relative to the body to afford a comparison between the sensory (e.g., kinesthetic) reafferences and the commands that generate limb movement. Here we propose that the superior parietal lobule (Brodmann area 5) might represent a substrate for a body-centered positional code. Monkeys made arm movements in different parts of 3D space in a reaction-time task. We found that the activity of area 5 neurons can be related to either the starting point, or the final point, or combinations of the two. Neural activity is monotonically tuned in a body-centered frame of reference, whose coordinates define the azimuth, elevation, and distance of the hand. Each spatial coordinate tends to be encoded in a different subpopulation of neurons. This parcellation could be a neural correlate of the psychophysical observation that these spatial parameters are processed in parallel and largely independent of each other in man.
Lacquaniti
F
F
Istituto di Fisiologia umana, Università di Cagliari, Italy.
Guigon
E
E
Bianchi
L
L
Ferraina
S
S
Caminiti
R
R
D000818:Animals; D001132:Arm / Q000294:innervation / Q000502:physiology; D004594:Electrophysiology; D008254:Macaca nemestrina; D008839:Microelectrodes; D008959:Models, Neurological; D009068:Movement / Q000502:physiology*; D009474:Neurons / Q000502:physiology; D009949:Orientation / Q000502:physiology; D010296:Parietal Lobe / Q000033:anatomy & histology / Q000166:cytology / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D013028:Space Perception / Q000502:physiology*