Sex differences in SEP (Somatosensory Evoked Potential) and EEG were studied with 90 healthy adult males (mean age=25.3±3.1 y.o.) and 96 adult females (mean age=21.6±2.7 y. o.). SEPs evoked by median nerve stimuli were recorded with 1000 msec of analysis time through the two derivations (bipolar: C3’→F3’ and monopolar : C3’→A1+2). The differences between the two group mean SEPs of each sex were studied. The differences in latencies and interpeak amplitudes of individual SEPs between sexes were tested statistically. The following results were obtained.
1. In the waveform of group mean SEP, there were differencies between N 3 and P 6, with P 4 (bipolar), and P 5, N 5 (monopolar) for females but not for males. The latencies of most of components were shorter, and interpeak amplitudes were larger in females than in males.
2. In the individual SEP most of latencies were significantly shorter and interpeak amplitudes were significantly larger in females than in males.
3. The significant sex differences in latencies and amplitudes of SEP components were verified even after excluding the influences of age and stature, by analysis of covariance.
4. In EEG, θ, β 1 and β 2 power % were larger, and δ and α 2 power % were smaller in fem ales than in males.
The sex differences in SEP verified in this study might be attributed to larger corpus callosum and less differentiated lateralities of the brain in females than in males, and the differences in sex hormon between the two sexes
