PMID-7143039 On the relations between the direction of two-dimensional arm movements and cell discharge in primate motor cortex.
- eight directions 45deg intervals, 2D joystick, frictionless, LED tarkets in a blocked randomized experimental design.
- MK made simultaneous saccades; saccade latency 150-170ms.
- some motor cells responded to visual movement.
- EMG activity began ~80ms before movement.
- monkeys used both arms.
- bell-shaped or cosine tuning in 75% of the cells.
- This has also been described in the saccade system in the paramedian pontine reticular formation (Henn and Cohen 1976), the mesencelphatic reticular formation (Buttner eta la 1977) and the internal medullary lamina of the thalamus (Schlag and Schlag-Ney 1977)
- cells tended to cluster by tuning in depth.
- cells tended to respond to movement & small corrections to movement, but did not necessarily respond to non-task related movement. "Yet these same cells were frequently silent during other movements which also involved contraction of the same muscles [as used in the task]"
- cell discharge was much stronger during active movements than during passive manipulations.
- 64% of cells were activated before the earliest EMG changes; 87% before the onset of movement.
- The famous one, where the population vector was formalized / conceived / validated.
- most neurons begin firing ~ 100ms before movement begins.
- useda PDP11/20 minicomputer to control the LEDs & data recording.
- Thach 1978 -- approxmately equal proportions of motor cortical cells were related to muscle activity, hans position, and direction of intended movement Thach 1978) PMID-96223
- single electrode Pt/Ir recording 2-3Mohm; recordings made for 6-7 hours.
- cite georgopoulos 1983 -- they propose distributed population coding.
- point out that the central problem -- upon which some progress has been made - is the translation between visual and motor coordinate frames.
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