Visual evoked potentials in the vicinity of the optic tract during stereotactic pallidotomy

Shozo Tobimatsu, Fumio Shima, Katsuya Ishido, Motohiro Kato

    Research output: Contribution to journalArticlepeer-review

    25 Citations (Scopus)


    We recorded visual evoked responses in eight patients with Parkinson's disease, using a depth electrode either at or below the stereotactic target in the ventral part of the globus pallidus internus (GPi), which is located immediately dorsal to the optic tract. Simultaneously, scalp visual evoked potentials (VEPs) were also recorded from a mid-occipital electrode with a mid-frontal reference electrode. A black-and-white checkerboard pattern was phase reversed at 1 Hz; check size was 50 min of arc. Pallidal VEPs to full field stimulation showed an initial positive deflection, with a latency of about 50 ms (P50) followed by a negativity with a mean latency of 80 ms (NSI). The mean onset latency of P50 was about 30 ms, P50 and N80 were limited to the ventralmost of the GPi and the ansa lenticularis. Left half field stimulation evoked responses in the right ansa lenticularis region while right half field stimulation did not, and vice versa. These potentials thus seemed to originate posterior to the optic chiasm. The scalp VEPs showed typical triphasic wave forms consisting of N75, P100 and N145. The location of the recording electrode in the ansa lenticularis region did not modify the scalp VEP. These results suggest that P50 and N80 are near field potentials reflecting the compound action potentials from the optic tract. Therefore, N75 of the scalp VEPs may represent an initial response of the striate cortex but not of the lateral geniculate nucleus.

    Original languageEnglish
    Pages (from-to)274-279
    Number of pages6
    JournalElectroencephalography and Clinical Neurophysiology - Evoked Potentials
    Issue number3
    Publication statusPublished - May 1997

    All Science Journal Classification (ASJC) codes

    • General Neuroscience
    • Clinical Neurology


    Dive into the research topics of 'Visual evoked potentials in the vicinity of the optic tract during stereotactic pallidotomy'. Together they form a unique fingerprint.

    Cite this