Attention modulates somatosensory cerebral blood flow response to vibrotactile stimulation as measured by positron emission tomography.

In human primary somatosensory cortex, the cerebral blood flow response to vibrotactile stimulation of the fingers (110 Hz), as measured by positron emission tomography and H2(15)O, was 13% higher (p less than 0.025) when the subjects attended to the stimulus, compared to when they were simultaneously engaged in a distraction task. This suggests that the physiological response of a primary cortical area can be modulated by the attentive behavior of the subject.