Functional Magnetic Resonance Imaging Assessment of the Human Brain Auditory Cortex Response to Increasing Word Presentation Rates. Dhankhar, Ajay, Bruce E. Wexler, Robert K. Fulbright, Terry Halwes, Andrew M. Blamire and Robert G. Shulman. Departments of Psychiatry, Radiology, Neurosurgery, and Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, CT 06510.
APStracts 3:0213N, 1996.
In an investigation of the auditory cortex response to speech, six subjects were studied using echo-planar functional Magnetic Resonance Imaging (fMRI) at 2.1T. The subjects were asked to listen to English nouns presented at various rates ranging from 0 words per minute (wpm) to 130 wpm while fMRI images encompassing their primary and posterior superior secondary auditory cortices were acquired. An asymmetric spin echo imaging sequence was used with an induced T 2 * weighting of 50 ms to allow for transverse relaxation effects. Images were acquired in two or four axial-oblique slices with a repetition time of 3.75 or 7.5 s, in plane resolution of 6 x 3 mm, and a slice thickness of 5mm. Localized activation centered over grey matter was consistently observed in all subjects in the transverse temporal gyrus (TTG), the transverse temporal sulcus (TTS), and the posterior superior aspect of the superior temporal gyrus (STG). The total activated volume and the integrated signal response in bilateral primary and posterior superior secondary auditory cortices increased with increasing rate of word presentation, peaking at 90 wpm (with some intersubject variability) with a subsequent fall at 130 wpm. There were no significant differences in the rate dependence of the signal response in bilateral primary and bilateral posterior superior secondary auditory cortices (p < 0.05).

Received 11 December 1995; accepted in final form 3 September 1996.
APS Manuscript Number J836-5.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 7 October 1996