VISUAL EVOKED-POTENTIAL FROM SCALP IN GUINEA-PIGS

Visual evoked potentials (VEPs) recorded from the scalp in guinea pigs were compared with those from the dura. The study was performed with ten adult male guinea pigs weighing 350-750 g. VEPs recorded from the scalp had large negative components (N40 and N75) and a large positive component (P55). The waveform of the VEP in the scalp recording was similar to that in the dural recording in that N40 was a major early negative component. Great differences between the scalp and the dural recording were observed in the late negative components (N75 and N140). In the dural recording, the peak N75 was a very small component, and the peak N140 was very large. There was no significant difference between the peak latencies of the two kinds of VEPs except for the peaks P55 and P100. Peak-to-peak amplitudes of VEPs recorded from the scalp were smaller than those from the dura except for P55-N75. The peak-to-peak amplitude in the scalp recording compared to that in the dural recording varied from a ratio as low as 1.0:2.9 to as high as 1.0:36.2, and was markedly variable in each component. The scalp recording correlated with the dural recording as regards the early component.