[lingtalks] Stephen Wilson 4/30 (Linguistics Colloquium)

[Klinton Bicknell]

On Monday 30 April at 2pm, Stephen Wilson (UC-Irvine; 
http://lcbr.ss.uci.edu/wilson/) will give a colloquium at the UCSD 
Linguistics Department, in AP&M 4301.

:: Abstract ::

Neuroimaging studies of the role of speech motor areas in speech perception
Stephen M. Wilson, UC-Irvine

The role of superior temporal cortex in speech perception is well 
established, but there is also much evidence suggestive of an ancillary 
role for frontal speech motor areas in the perceptual process. A series 
of studies using functional magnetic resonance imaging (fMRI) and 
transcranial magnetic stimulation (TMS) will be presented in support of 
this idea. In the first study, subjects listened passively to 
monosyllables, and produced the same speech sounds. Listening to speech 
activated a premotor cortical region largely overlapping a speech 
production motor area centered just posteriorly. These findings support 
the view that the motor system is recruited in mapping the acoustic 
signal to a phonetic code. The next study examined neural responses to 
unfamiliar non-native phonemes varying in the extent to which they can 
be articulated. Both superior temporal (auditory) and precentral (motor) 
areas were activated by passive speech perception, and both 
distinguished non-native from native phonemes. Furthermore, 
speech-responsive motor regions and superior temporal sites were 
functionally connected. However, only in auditory areas did activity 
covary with the producibility of non-native phonemes. These data suggest 
that auditory areas are crucial for the transformation from acoustic 
signal to phonetic code, but the motor system also plays an active role, 
perhaps in generating candidate phonemic categorizations. A third study 
aimed to determine whether speech motor regions are crucial for speech 
perception or merely coactivated. We used repetitive TMS to create a 
“virtual lesion” in left premotor cortex while subjects performed a 
speech perception task and a matched color perception task. Performance 
was disrupted on the speech perception task, but not on the control 
task, suggesting that this speech motor region is in fact necessary for 
speech perception. In sum, these studies motivate an important role for 
speech motor areas in the perception of speech.

--

For further information about the Linguistics department colloquia 
series, including the schedule of future events, please visit 
http://ling.ucsd.edu/events/colloquia.html .