Somatosensory evoked potentials to a threshold air-puff can predict stimulus detection in human subjects

Somatosensory evoked potentials (SEPs) and reaction time (RT) were studied following a threshold intensity air-puff stimulation of the skin in nine subjects. We delivered brief air-puffs, at the threshold intensity of about 50% detection probability, to the volar surface of the right hand at the base of the index finger. The SEPs were averaged separately for detected and undetected stimuli. Prior to the SEP data collection, RTs to the same intensity threshold stimulus were measured. P300 SEP late component was recorded in response to detected stimuli and was not to undetected stimuli. However, in one subject, P300 was associated with undetected stimuli, suggesting errors in the psychophysical task. The peak latency of P300 was 316+/-29 ms (mean+/-SD) and earlier than the average RT (390+/-43 ms). These results demonstrate that SEPs can correctly predict perception of the threshold air-puff stimulus.