Run, don't walk, to your nearest library or computer terminal!
A new paper by Huan Luo and me just appeared in Neuron. Huan was a graduate student in the University of Maryland Neuroscience and Cognitive Science program and worked principally with me and Jonathan Simon. She finished her Ph.D in 2006, and is now living in Beijing with her husband and two children. Yes, she was ridiculously productive in graduate school ...
This paper shows (IMHO) compelling evidence (based on single trial MEG data) that speech is analyzed using a ~200 ms window.
Luo, H. & Poeppel, D. (2007). Phase Patterns of Neuronal Responses Reliably Discriminate Speech in Human Auditory Cortex. Neuron 54, 1001-1010.
How natural speech is represented in the auditory cortex constitutes a major challenge for cognitive neuroscience. Although many single-unit and neuroimaging studies have yielded valuable insights about the processing of speech and matched complex sounds, the mechanisms underlying the analysis of speech dynamics in human auditory cortex remain largely unknown. Here, we show that the phase pattern of theta band (4–8 Hz) responses recorded from human auditory cortex with magnetoencephalography (MEG) reliably tracks and discriminates spoken sentences and that this discrimination ability is correlated with speech intelligibility. The findings suggest that an ∼200 ms temporal window (period of theta oscillation) segments the incoming speech signal, resetting and sliding to track speech dynamics. This hypothesized mechanism for cortical speech analysis is based on the stimulus-induced modulation of inherent cortical rhythms and provides further evidence implicating the syllable as a computational primitive for the representation of spoken language.