Plasticity revealed by transcranial magnetic stimulation of early visual cortex.
We applied single-pulse transcranial magnetic stimulation (TMS) to the occipital pole of healthy subjects while they performed a forced-choice visual letter-identification task. We found three separate periods when TMS suppressed performance; the first period is best explained by TMS-induced blinking whereas the last two periods are best explained by TMS-induced disruption of letter-processing in the early visual cortex. Unexpectedly, we also found that TMS-induced suppression progressively disappeared during three weeks of repeated TMS experiments. However, it was only suppression during the last two periods that disappeared; suppression during the first period remained undiminished. When subjects were then presented with dimmer letters, suppression reappeared. The most likely explanation is a practice-induced increase in neuronal activity in the early visual cortex.
Corthout
E
E
Department of Experimental Psychology, Oxford, UK.
Uttl
B
B
Walsh
V
V
Hallett
M
M
Cowey
A
A
D000328:Adult; D004558:Electric Stimulation; D005260:Female; D006801:Humans; D008297:Male; D009473:Neuronal Plasticity / Q000502:physiology*; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010775:Photic Stimulation; D050781:Transcranial Magnetic Stimulation; D014793:Visual Cortex / Q000502:physiology*