Impact of Audio-Visual Asynchrony on Lip-Reading Effects -Neuromagnetic and Psychophysical Study-

Abstract

The effects of asynchrony between audio and visual (A/V) stimuli on the N100m responses of magnetoencephalography in the left hemisphere were compared with those on the psychophysical responses in 11 participants. The latency and amplitude of N100m were significantly shortened and reduced in the left hemisphere by the presentation of visual speech as long as the temporal asynchrony between A/V stimuli was within 100 ms, but were not significantly affected with audio lags of -500 and +500 ms. However, some small effects were still preserved on average with audio lags of 500 ms, suggesting similar asymmetry of the temporal window to that observed in psychophysical measurements, which tended to be more robust (wider) for audio lags; i.e., the pattern of visual-speech effects as a function of A/V lag observed in the N100m in the left hemisphere grossly resembled that in psychophysical measurements on average, although the individual responses were somewhat varied. The present results suggest that the basic configuration of the temporal window of visual effects on auditory-speech perception could be observed from the early auditory processing stage.

Awake state-specific suppression of primary somatosensory evoked response correlated with duration of temporal lobe epilepsy

“…MEG was performed with a 200-channel whole-head MEG system with axial gradiometers (RICOH Ltd., Tokyo, Japan) in a magnetically shielded room. The detailed conditions of the MEG system used in this study have already been described 38 , 39 . Briefly, the sensors were first-order axial gradiometers with a baseline of 50 mm and 15.5-mm diameter coils.…”

“…All patients and subjects lay in the supine position, with the head location determined by the positions of five fiduciary markers consisting of induction coils placed at known locations on the scalp. The head shape and coil positions were established using a three-dimensional digitizer (FastSCAN Cobra, Polhemus, Inc., Colchester, VT) based on three-dimensional MR images obtained for all patients and subjects using a 3T MR system (Achieva, Philips Healthcare, Best, the Netherlands; or Magnetom Trio, Siemens AG, Erlangen, Germany) 38,39 .…”

Scalp attached tangential magnetoencephalography using tunnel magneto-resistive sensors

“…The sensors are arranged in a uniform array on a helmet-shaped surface at the bottom of a Dewar vessel, and the mean distance between the centers of two adjacent coils is 25 mm. Sensor eld sensitivity (noise of the system) was 3 fT/Hz within the frequency range for SEFs 25,26 . The subjects lay supine, with the head location determined by the positions of ve duciary markers consisting of induction coils placed at known locations on the scalp.…”