Independence of early speech processing from word meaning.

TitleIndependence of early speech processing from word meaning.
Publication TypeJournal Article
Year of Publication2013
AuthorsTravis KE, Leonard MK, Chan AM, Torres C, Sizemore ML, Qu Z, Eskandar E, Dale AM, Elman JL, Cash SS, Halgren E
JournalCereb Cortex
Date Published2013 Oct
KeywordsAdult, Brain, Brain Mapping, Female, Humans, Magnetic Resonance Imaging, Magnetoencephalography, Male, Speech Perception, Young Adult

We combined magnetoencephalography (MEG) with magnetic resonance imaging and electrocorticography to separate in anatomy and latency 2 fundamental stages underlying speech comprehension. The first acoustic-phonetic stage is selective for words relative to control stimuli individually matched on acoustic properties. It begins ∼60 ms after stimulus onset and is localized to middle superior temporal cortex. It was replicated in another experiment, but is strongly dissociated from the response to tones in the same subjects. Within the same task, semantic priming of the same words by a related picture modulates cortical processing in a broader network, but this does not begin until ∼217 ms. The earlier onset of acoustic-phonetic processing compared with lexico-semantic modulation was significant in each individual subject. The MEG source estimates were confirmed with intracranial local field potential and high gamma power responses acquired in 2 additional subjects performing the same task. These recordings further identified sites within superior temporal cortex that responded only to the acoustic-phonetic contrast at short latencies, or the lexico-semantic at long. The independence of the early acoustic-phonetic response from semantic context suggests a limited role for lexical feedback in early speech perception.

Alternate JournalCereb. Cortex
PubMed ID22875868
PubMed Central IDPMC3767959
Grant ListDC000041 / DC / NIDCD NIH HHS / United States
MH020002 / MH / NIMH NIH HHS / United States
R01 NS018741 / NS / NINDS NIH HHS / United States
R01 NS018741 / NS / NINDS NIH HHS / United States
R01-DC005650 / DC / NIDCD NIH HHS / United States
T32 MH020002 / MH / NIMH NIH HHS / United States
IRG Funded