Cerebral dynamics of SEPs to non-painful and painful cutaneous electrical stimulation of the thenar and hypothenar

Early, middle and late latency somatosensory evoked potentials (SEPs) elicited by cutaneous electrical stimulation (painful vs. non-painful) of right and left hands were recorded. The aims were to study (1) if lifelong use of dominant right hand would result in different SEP topographies compared to non-dominant left hand stimulation, (2) if painful and non-painful stimuli resulted in different SEP activation patterns for the different latency components and (3) if these results were consistent between two areas of the hand. Electrical stimuli were applied cutaneously above the thenar and hypothenar muscles of the left and right hand. A two-way repeated measures ANOVA was used to test the effects of laterality and intensity for a given peak amplitude and latency. Statistical results yielded no significant difference in peak amplitude for either thenar and hypothenar between the two hands. In contrast, a significant difference in amplitude was observed for 6 components for each stimulus location when the two intensities were compared. These components were found at early, middle and late latencies. No significant latency shift was observed between the two hands. Only the P30 component showed a significant latency shift for both locations with the painful condition having the shorter latency. Thus, life-long use of the dominant hand does not generate detectable changes in cortical evoked activity to sensory input from the skin above thenar and hypothenar muscles. Several SEP components across the time course (0-400 ms) showed increased amplitude when the stimulus was increased from non-painful to painful intensity.