Effects of Place of Articulation Changes on Auditory Neural Activity: A Magnetoencephalography Study

In casual speech, phonemic segments often assimilate such that they adopt features from adjacent segments, a typical feature being their place of articulation within the vocal tract (e.g., labial, coronal, velar). Place assimilation (e.g., from coronal /n/ to labial /m/: rainbow→*raimbow) alters the surface form of words. Listeners' ability to perceptually compensate for such changes seems to depend on the phonemic context, on whether the adjacent segment (e.g., the /b/ in “rainbow”) invites the particular change. Also, some assimilations occur frequently (e.g., /n/→/m/), others are rare (e.g., /m/→/n/). We investigated the effects of place assimilation, its contextual dependency, and its frequency on the strength of auditory evoked mismatch negativity (MMN) responses, using pseudowords. Results from magnetoencephalography (MEG) revealed that the MMN was modulated both by the frequency and contextual appropriateness of assimilations

Predictions of the three main approaches with respect to the issues under investigation.

<p>Predictions of the three main approaches with respect to the issues under investigation.</p

Mean amplitude of the identity mismatch (iMMN) in 170–410 ms post-stimulus interval.

<p>The iMMN reflects oddball effects on the same speech token presented as deviant and standard across stimulation blocks. As predicted, an asymmetry in mismatch activity was observed between specified and underspecified segments only for contextually appropriate cases. Compared to the frequent (/n/ to /m/) change from the appropriate context, all other conditions showed significant enhancements in mismatch amplitude. Error bars represent 95% confidence intervals.</p

Stimulus material.

<p>Disyllabic VC₁C₂V pseudowords created by cross-splicing, mixing, and rejoining segments edited from recorded speech.</p

Grand-averaged source waveforms for the experimental odd-ball sequences contrasting frequent/infrequent nasal place feature assimilations embedded in appropriate/inappropriate phonemic context.

<p>Robust mismatch activity was present in both hemispheres in all conditions in the interval 170–410 ms following stimulus (shown below the left panel) onset.</p

MNE-BIDS: Organizing electrophysiological data into the BIDS format and facilitating their analysis

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