Finger movements induced by transcranial magnetic stimulation change with hand posture, but not with coil position
We attempted to map the representations of movements in 2 normal subjects by delivering five transcranial magnetic stimuli (TMS) with a focal coil to each of a grid of positions over the primary motor area (M1). Isometric forces were recorded from the contralateral index finger. Maps were made with the hand in a semiflexed “neutral” position, and with the thumb and index finger opposed in a “pincer” grip. The electromyogram (EMG) was monitored to ensure relaxation. The wrist was immobilized. In the neutral position, TMS at almost all positions produced abduction. Flexion was produced in the pincer position. Thus, while sensitive to changes in posture, TMS mapping may not be sensitive to the…
The role of the dorsolateral prefrontal cortex in implicit procedural learning.
We studied the role of the dorsolateral prefrontal cortex in procedural learning. Normal subjects completed several blocks of a serial reaction time task using only one hand without or with concurrent non-invasive repetitive transcranial magnetic stimulation. To disrupt their function transiently, stimulation was applied at low intensity over the supplementary motor area or over the dorsolateral prefrontal cortex contralateral or ipsilateral to the hand used for the test. Stimulation to the contralateral dorsolateral prefrontal cortex markedly impaired procedural implicit learning, as documented by the lack of significant change in response times during the task. Stimulation over the other …