TY - JOUR
T1 - Mapping phonemic processing zones along human perisylvian cortex
T2 - An electro-corticographic investigation
AU - Molholm, Sophie
AU - Mercier, Manuel R.
AU - Liebenthal, Einat
AU - Schwartz, Theodore H.
AU - Ritter, Walter
AU - Foxe, John J.
AU - De Sanctis, Pierfilippo
N1 - Funding Information:
The authors wish to express their sincere appreciation to the participants who kindly donated their time to this project, to Mr. Jason Adler for his contribution to the analysis of data, and to Ms. Edel Flynn for assistance with manuscript formatting. SM and JJF received support from NIMH (MH 85322) and a grant from the Nathan Gancher Foundation, and MM from the Swiss National Science Foundation (PBELP3-123067).
PY - 2014/7
Y1 - 2014/7
N2 - The auditory system is organized such that progressively more complex features are represented across successive cortical hierarchical stages. Just when and where the processing of phonemes, fundamental elements of the speech signal, is achieved in this hierarchy remains a matter of vigorous debate. Non-invasive measures of phonemic representation have been somewhat equivocal. While some studies point to a primary role for middle/anterior regions of the superior temporal gyrus (STG), others implicate the posterior STG. Differences in stimulation, task and inter-individual anatomical/functional variability may account for these discrepant findings. Here, we sought to clarify this issue by mapping phonemic representation across left perisylvian cortex, taking advantage of the excellent sampling density afforded by intracranial recordings in humans. We asked whether one or both major divisions of the STG were sensitive to phonemic transitions. The high signal-to-noise characteristics of direct intracranial recordings allowed for analysis at the individual participant level, circumventing issues of inter-individual anatomic and functional variability that may have obscured previous findings at the group level of analysis. The mismatch negativity (MMN), an electrophysiological response elicited by changes in repetitive streams of stimulation, served as our primary dependent measure. Oddball configurations of pairs of phonemes, spectro-temporally matched non-phonemes, and simple tones were presented. The loci of the MMN clearly differed as a function of stimulus type. Phoneme representation was most robust over middle/anterior STG/STS, but was also observed over posterior STG/SMG. These data point to multiple phonemic processing zones along perisylvian cortex, both anterior and posterior to primary auditory cortex. This finding is considered within the context of a dual stream model of auditory processing in which functionally distinct ventral and dorsal auditory processing pathways may be engaged by speech stimuli.
AB - The auditory system is organized such that progressively more complex features are represented across successive cortical hierarchical stages. Just when and where the processing of phonemes, fundamental elements of the speech signal, is achieved in this hierarchy remains a matter of vigorous debate. Non-invasive measures of phonemic representation have been somewhat equivocal. While some studies point to a primary role for middle/anterior regions of the superior temporal gyrus (STG), others implicate the posterior STG. Differences in stimulation, task and inter-individual anatomical/functional variability may account for these discrepant findings. Here, we sought to clarify this issue by mapping phonemic representation across left perisylvian cortex, taking advantage of the excellent sampling density afforded by intracranial recordings in humans. We asked whether one or both major divisions of the STG were sensitive to phonemic transitions. The high signal-to-noise characteristics of direct intracranial recordings allowed for analysis at the individual participant level, circumventing issues of inter-individual anatomic and functional variability that may have obscured previous findings at the group level of analysis. The mismatch negativity (MMN), an electrophysiological response elicited by changes in repetitive streams of stimulation, served as our primary dependent measure. Oddball configurations of pairs of phonemes, spectro-temporally matched non-phonemes, and simple tones were presented. The loci of the MMN clearly differed as a function of stimulus type. Phoneme representation was most robust over middle/anterior STG/STS, but was also observed over posterior STG/SMG. These data point to multiple phonemic processing zones along perisylvian cortex, both anterior and posterior to primary auditory cortex. This finding is considered within the context of a dual stream model of auditory processing in which functionally distinct ventral and dorsal auditory processing pathways may be engaged by speech stimuli.
KW - Auditory
KW - ECog
KW - Intracranial
KW - Phoneme
KW - Speech processing
KW - Superior temporal gyrus
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U2 - 10.1007/s00429-013-0574-y
DO - 10.1007/s00429-013-0574-y
M3 - Article
C2 - 23708059
AN - SCOPUS:84904331544
SN - 1863-2653
VL - 219
SP - 1369
EP - 1383
JO - Brain Structure and Function
JF - Brain Structure and Function
IS - 4
ER -