A Ticklish Question: Does Magnetic Stimulation of the Primary Motor Cortex Give Rise to an ‘Efference copy’?

In order to make accurate predictions about the somatosensory consequences of our own movements, an ‘efference copy’ of motor output appears to be used (probably in the cerebellum) as a basis for anticipating and canceling incoming information about self-produced movement. One everyday phenomenon that results from these predictive processes is that of being unable to tickle oneself. We examined whether involuntary movements induced by magnetic stimulation of (a) the motor cortex and (b) the bicep muscle, both resulting in standard stimulation of the participantʹs bare foot, would be perceived as ticklish. In both cases, the stimulus to the foot was rated as ticklish as when the experimenter tickled the participantʹs foot (using an identical stimulus). We conclude that magnetic stimulation of the motor cortex is unlikely to give rise to an efference copy of motor output.