Brain Structure and Function

, Volume 219, Issue 4, pp 1369–1383

Mapping phonemic processing zones along human perisylvian cortex: an electro-corticographic investigation

  • Sophie Molholm
  • Manuel R. Mercier
  • Einat Liebenthal
  • Theodore H. Schwartz
  • Walter Ritter
  • John J. Foxe
  • Pierfilippo De Sanctis
Original Article

DOI: 10.1007/s00429-013-0574-y

Cite this article as:
Molholm, S., Mercier, M.R., Liebenthal, E. et al. Brain Struct Funct (2014) 219: 1369. doi:10.1007/s00429-013-0574-y

Abstract

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.

Keywords

ECogPhonemeSuperior temporal gyrusAuditorySpeech processingIntracranial

Supplementary material

429_2013_574_MOESM1_ESM.tif (419 kb)
Supplementary material 1 (TIFF 419 kb)

Copyright information

© Springer-Verlag Berlin Heidelberg 2013

Authors and Affiliations

  • Sophie Molholm
    • 1
    • 2
  • Manuel R. Mercier
    • 1
  • Einat Liebenthal
    • 3
  • Theodore H. Schwartz
    • 4
  • Walter Ritter
    • 1
  • John J. Foxe
    • 1
    • 2
  • Pierfilippo De Sanctis
    • 1
  1. 1.The Sheryl and Daniel R. Tishman Cognitive Neurophysiology Laboratory, Departments of Pediatrics and NeuroscienceChildren’s Evaluation and Rehabilitation Center (CERC), Albert Einstein College of MedicineBronxUSA
  2. 2.The Cognitive Neurophysiology LaboratoryThe Nathan S. Kline Institute for Psychiatric ResearchOrangeburgUSA
  3. 3.Department of NeurologyMedical College of WisconsinMilwaukeeUSA
  4. 4.Department of Neurological SurgeryWeill Cornell Medical College, New York Presbyterian HospitalNew YorkUSA