Interhemispheric transmission: assessment with vibratory somatosensory evoked potentials

Interhemispheric transmission time (ITT) was derived from vibratory somatosensory evoked potentials (VSEP) arising in homologous cortical sensory--association areas of normals. Two different vibratory sources, an audiometer bone oscillator or an Optacon, were used to stimulate each index finger independently. ITT was calculated by subtracting the latency of the first major peak over the contralateral cortex (CL) from the latency of the corresponding peak over the ipsilateral area (IL-CL = ITT). Readily identified aberrant values were observed and rejected from the series of measurements leaving clear normal ranges. In addition to providing normal ITT data, clinical correlations were illustrated in two different disorders. Results suggested that important information relating to diagnosis and therapy of brain pathologies affecting interhemispheric transmission can now be made available in both experimental and clinical situations.