Sublexical Properties of Spoken Words Modulate Activity in Broca's Area but Not Superior Temporal Cortex: Implications for Models of Speech Recognition

Many models of spoken word recognition posit that the acoustic stream is parsed into phoneme level units, which in turn activate larger representations [McClelland, J. L., & Elman, J. L. The TRACE model of speech perception. 1–86, 1986], whereas others suggest that larger units of analysis are a...

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Published in:	Journal of cognitive neuroscience 2011-10, Vol.23 (10), p.2665-2674
Main Authors:	Vaden, Kenneth I., Piquado, Tepring, Hickok, Gregory
Format:	Article
Language:	eng
Subjects:	Acoustic Stimulation - methods Adolescent Adult Analysis of Variance Brain Brain Mapping Cognitive psychology Female Frontal Lobe - blood supply Frontal Lobe - physiology Functional Laterality Humans Image Processing, Computer-Assisted Magnetic Resonance Imaging Male NMR Nuclear magnetic resonance Oxygen - blood Pattern Recognition, Physiological - physiology Reaction Time - physiology Speech Speech - physiology Speech Perception - physiology Temporal Lobe - blood supply Temporal Lobe - physiology Vocabulary Voice recognition Young Adult
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Summary:	Many models of spoken word recognition posit that the acoustic stream is parsed into phoneme level units, which in turn activate larger representations [McClelland, J. L., & Elman, J. L. The TRACE model of speech perception. 1–86, 1986], whereas others suggest that larger units of analysis are activated without the need for segmental mediation [Greenberg, S. A multitier theoretical framework for understanding spoken language. In S. Greenberg & W. A. Ainsworth (Eds.), (pp. 411–433). Mahwah, NJ: Erlbaum, 2005; Klatt, D. H. Speech perception: A model of acoustic-phonetic analysis and lexical access. 279–312, 1979; Massaro, D. W. Preperceptual images, processing time, and perceptual units in auditory perception. 124–145, 1972]. Identifying segmental effects in the brain's response to speech may speak to this question. For example, if such effects were localized to relatively early processing stages in auditory cortex, this would support a model of speech recognition in which segmental units are explicitly parsed out. In contrast, segmental processes that occur outside auditory cortex may indicate that alternative models should be considered. The current fMRI experiment manipulated the phonotactic frequency (PF) of words that were auditorily presented in short lists while participants performed a pseudoword detection task. PF is thought to modulate networks in which phoneme level units are represented. The present experiment identified activity in the left inferior frontal gyrus that was positively correlated with PF. No effects of PF were found in temporal lobe regions. We propose that the observed phonotactic effects during speech listening reflect the strength of the association between acoustic speech patterns and articulatory speech codes involving phoneme level units. On the basis of existing lesion evidence, we interpret the function of this auditory–motor association as playing a role primarily in production. These findings are consistent with the view that phoneme level units are not necessarily accessed during speech recognition.
ISSN:	0898-929X 1530-8898