A theoretical exploration of speech/neural oscillation alignment for speech parsing
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1
ENS, France
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2
INSERM, France
Recent neurophysiological and behavioral studies suggest a role of gamma and theta cortical oscillations in speech parsing at two timescales, a short one for phonemic analysis (gamma) and a long one for syllabic integration (theta, Giraud et al., 2007; Ghitza & Greenberg, 2009). It has also been observed that the phase of the theta rhythm tracks stimulus dynamics (Luo & Poeppel, 2007) and modulates gamma power (Lakatos et al., 2005). This property raises the issue of the alignment between cortical oscillations and the speech stimulus. A likely hypothesis is that gamma power is high when the more informative parts of the speech signal are to be analyzed, and low when speech provides no phonological information, typically during the steady part of vowels and silences. The aim of this theoretical work is to design a biophysical model of nested gamma/theta oscillations (Shamir et al., 2009), where gamma power aligns with speech acoustic edges. We designed a neurophysiologically plausible model of theta/gamma where a PING network (Börgers & Kopell, 2005) is modulated by a PINTH (pyramidal interneuron theta) network. In conventional models of gamma/theta nesting (e.g. Kopell et al., 2010), a common reset of PING and PINTH by stimulus onset results in an initial gamma depression that is incompatible with the proposed function of the model. We therefore suggest that oscillatory activity is more sustained at rest than initially postulated in such models, which results in a release of gamma activity upon stimulus onset signal. Neural oscillatory activity can thus be engaged by the stimulus and immediately efficient for parsing. This view is compatible with experimental data showing that gamma and theta activity are already detectable at rest in auditory cortices.
Keywords:
Language,
Speech
Conference:
XI International Conference on Cognitive Neuroscience (ICON XI), Palma, Mallorca, Spain, 25 Sep - 29 Sep, 2011.
Presentation Type:
Poster Presentation
Topic:
Poster Sessions: Neural Bases of Language
Citation:
Hyafil
A,
Gutkin
B and
Giraud
A
(2011). A theoretical exploration of speech/neural oscillation alignment for speech parsing.
Conference Abstract:
XI International Conference on Cognitive Neuroscience (ICON XI).
doi: 10.3389/conf.fnhum.2011.207.00201
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Received:
21 Nov 2011;
Published Online:
28 Nov 2011.
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Correspondence:
Dr. Alexandre Hyafil, ENS, Paris, France, alexandre.hyafil@gmail.com