The basic mechanisms underlying comprehension of spoken language are unknown. We do not understand, for example, how the human brain extracts the most fundamental linguistic elements (consonants and vowels) from a complex and highly variable acoustic signal. An investigation of the cortical representation of speech sounds during categorical perception can likely shed light on this fundamental question. Categorical perception occurs when a change in a variable such as phonem ic contrast along a continuum is perceived, not as a gradual function but rather as a discrete category change. Previous research has implicated the superior temporal cortex in the processing Of speech sounds. However, how the cortex actually represents (i.e. encodes) phonemes is undetermined, mainly due to limitations of non-invasive recording techniques. The recording of neural activity di rectly from the cortical surface is a promising approach si nee it can provide both high spatial and temporal resolution. Here, I propose to examine the mechanisms of categorical speech processing by utilizing neurophysiological recordings obtained during ne urosurgical pnacedures. The principal focus of the independent ROO phase wil I be to elucidate the emergent invariant representation of phonemes in the superior tem poral gyrus that underiies categorical perception. High-density electrode anays, advanced signal processing, and direct eiectrocortical stim ulation will be utilized to unravel both local population encoding of speec h sounds in the lateral temporal cortex as well as global processing across multiple sensory and cognitiv e areas.

Public Health Relevance

The ainn of this research is to reveal the fundamental mechanisnns that underlie comprehension of spoken language. An understanding of how speech is coded in the brain has signifieant implications for the development of new diagnostic and rehabilitative strategies for language disorders (e.g. aphasia, dyslexia, autism, et alia). Abnormal perception of phonemes is a central component to language disability in all of these conditions.

National Institute of Health (NIH)
National Institute of Neurological Disorders and Stroke (NINDS)
Research Transition Award (R00)
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Special Emphasis Panel (NSS)
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Babcock, Debra J
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University of California San Francisco
Schools of Medicine
San Francisco
United States
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Leonard, Matthew K; Chang, Edward F (2014) Dynamic speech representations in the human temporal lobe. Trends Cogn Sci 18:472-9
Bouchard, Kristofer E; Chang, Edward F (2014) Control of spoken vowel acoustics and the influence of phonetic context in human speech sensorimotor cortex. J Neurosci 34:12662-77
Conant, David; Bouchard, Kristofer E; Chang, Edward F (2014) Speech map in the human ventral sensory-motor cortex. Curr Opin Neurobiol 24:63-7
Mesgarani, Nima; Cheung, Connie; Johnson, Keith et al. (2014) Phonetic feature encoding in human superior temporal gyrus. Science 343:1006-10
Chang, Edward F; Niziolek, Caroline A; Knight, Robert T et al. (2013) Human cortical sensorimotor network underlying feedback control of vocal pitch. Proc Natl Acad Sci U S A 110:2653-8
Bouchard, Kristofer E; Mesgarani, Nima; Johnson, Keith et al. (2013) Functional organization of human sensorimotor cortex for speech articulation. Nature 495:327-32
Edwards, Erik; Chang, Edward F (2013) Syllabic (ýýý2-5ýýHz) and fluctuation (ýýý1-10ýýHz) ranges in speech andýýauditory processing. Hear Res 305:113-34
Mesgarani, Nima; Chang, Edward F (2012) Selective cortical representation of attended speaker in multi-talker speech perception. Nature 485:233-6
Chang, Edward F; Edwards, Erik; Nagarajan, Srikantan S et al. (2011) Cortical spatio-temporal dynamics underlying phonological target detection in humans. J Cogn Neurosci 23:1437-46
Chang, Edward F; Clark, Aaron; Smith, Justin S et al. (2011) Functional mapping-guided resection of low-grade gliomas in eloquent areas of the brain: improvement of long-term survival. Clinical article. J Neurosurg 114:566-73

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