Neural Bases of the Motor Theory of Speech Perception Tyler Perrachione HST.722 / 9.044J 11/1/2007...
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Transcript of Neural Bases of the Motor Theory of Speech Perception Tyler Perrachione HST.722 / 9.044J 11/1/2007...
Neural Bases of the Motor Theory of Speech Perception
Tyler PerrachioneHST.722 / 9.044J
11/1/2007
The Speech Chain(s)
Acoustic Variability and Phonological Invariance
• Formant trajectories• Aspiration following
sibilants• Coarticulation• Intra/inter-speaker
variation• Syllable position
Bonuses from Motor Theory
• Parsimonious w/r/t a unified system for production and perception
• Accounts for mapping between highly variable acoustic signal and invariant phonological percepts
• Consistent with perception as internal representation of distal events
Why is the Motor Theory Always the Alternative Theory?
• Lack of direct behavioral evidence
• Putatively less computationally efficient
• Less intuitive
• Skepticism about theories that are “too big”
• Haskins labs are a bunch of crackpots
New Evidence - fMRI
• Hearing speech activation overlaps regions of activation during the production of speech
(Wilson et al., 2004 Nat. Neurosci.)
New Evidence - fMRI
• Lip regions of motor cortex more active during perception of /p/, tongue regions more active during perception of /t/
(Pulvermüller et al., 2006, PNAS)
New Evidence - TMS
• Stimulation of prefrontal cortex impairs speech, not nonspeech, perception (Meister et al. 2007, Current Biology)
• Dissociable loci of phonological and semantic processing in IFG (Gough et al. 2005, J. Neurosci).
• Combined PET and TMS to locate speech perception modulation in IFG (Watkins & Paus, 2004, J. Cog. Neuro)
• Enhanced motor-evoked potential when listening to speech vs nonspeech (Watkins et al. 2003, Neuropsychologia)
Relation to Other Topics
• Somatic & auditory integration in DCN for spatial location perception => sensory & motor integration in IFG for speech perception
• Stuttering and production / perception feedback loop
• Putative human mirror-neuron system
• Lateralization of speech-language processes
Why Discuss Motor Theory?
• Sensorimotor integration in perception has implications beyond speech:– Conspecific identification, theory of mind,
internal world models / simulations
• Implications for diagnosis and treatment of speech-sound disorders
• Broader perspective on nature of speech / language integration and evolution