Low threshold motor effects produced by stimulation of area preinsularis (2pr.i) of the secondary sensory cortex in the cat; Input-output relationships

(1) Intracortical microstimulation (ICMS) delivered to area 2 preinsularis (area 2 pr. i) of the second somatosensory cortex, SII, elicited contralateral distal limb movements with threshold currents as low as 2 µA. (2) The effective sites for a particular movement were located in a small area within the depth of the cortex extending along the direction of the radial fibers. (3) Neurons in an area for a particular movement generally received peripheral input from the skin overlying the muscle to which the area projected. (4) ICMS in area 2 pr.i produced powerful monosynaptic as well as disynaptic activation of pyramidal tract neurons, suggesting that the effect was mediated by the pyramidal tract. (5) Ablation of the motor cortex did not eliminate or otherwise reduce the low threshold responses from area 2 pr.i suggesting that the described effect is independent of the motor cortex.