Submitted on August 23, 2008
Revised on May 8, 2009
Accepted on May 10, 2009
Comparison of time-frequency responses and the event-related potential to auditory speech stimuli in human cortex
Erik Edwards1*, Maryam Soltani2, Won Kim2, Sarang S. Dalal3, Mitchel S. Berger3, Srikantan Nagarajan3, and Robert T. Knight4
1 University of Washington, Seattle
2 University of California, Berkeley
3 University of California, San Francisco
4 Univ California Berkeley
* To whom correspondence should be addressed. E-mail: erik{at}socrates.berkeley.edu.
We recorded the electrocorticogram (ECoG) directly from the exposed cortical surface of awake neurosurgical patients during the presentation of auditory syllable stimuli. All patients were unanesthetized as part of a language mapping procedure for subsequent left-hemisphere tumor resection. Time-frequency analyses showed significant high-gamma (
high: 70-160 Hz) responses from the left superior temporal gyrus (STG), but no reliable response from the left inferior frontal gyrus (IFG). Alpha suppression (
: 7-14 Hz) and event-related potential (ERP) responses exhibited a more widespread topography. Across electrodes, the suppression from 200-450 ms correlated with the preceding (50-200 ms) high increase. The results are discussed in terms of the different physiological origins of these electrocortical signals.
