We used fMRI to examine neural responses when subjects experienced a tactile stimulus that was either self-produced or externally produced. The somatosensory cortex showed increased levels of activity when the stimulus was externally produced. In the cerebellum there was less activity associated with a movement that generated a tactile stimulus than with a movement that did not. This difference suggests that the cerebellum is involved in predicting the specific sensory consequences of movements and providing the signal that is used to attenuate the sensory response to self-generated stimulation. In this paper, we use regression analyses to test this hypothesis explicitly. Specifically, we predicted that activity in the cerebellum contributes to the decrease in somatosensory cortex activity during self-produced tactile stimulation. Evidence in favor of this hypothesis was obtained by demonstrating that activity in the thalamus and primary and secondary somatosensory cortices significantly regressed on activity in the cerebellum when tactile stimuli were self-produced but not when they were externally produced. This supports the proposal that the cerebellum is involved in predicting the sensory consequences of movements. In the present study, this prediction is accurate when tactile stimuli are self-produced relative to when they are externally produced, and is therefore used to attenuate the somatosensory response to the former type of tactile stimulation but not the latter.
Copyright 1999 Academic Press.