A coded VEP method to measure interhemispheric transfer time (IHTT)

Abstract

Interhemispheric transfer time (IHTT) is an important parameter for research on the information conduction time across the corpus callosum between the two hemispheres. There are several traditional methods used to estimate the IHTT, including the reaction time (RT) method, the evoked potential (EP) method and the measure based on the transcranial magnetic stimulation (TMS). The present study proposes a novel coded VEP method to estimate the IHTT based on the specific properties of the m-sequence. These properties include good signal-to-noise ratio (SNR) and high noise tolerance. Additionally, calculation of the circular cross-correlation function is sensitive to the phase difference. The method presented in this paper estimates the IHTT using the m-sequence to encode the visual stimulus and also compares the results with the traditional flash VEP method. Furthermore, with the phase difference of the two responses calculated using the circular cross-correlation technique, the coded VEP method could obtain IHTT results, which does not require the selection of the utilized component.