A Sparse Neural Code for Some Speech Sounds but Not for Others

作者：Scharinger Mathias^*; Bendixen Alexandra; Trujillo Barreto Nelson J; Obleser Jonas

来源：PLos One, 2012, 7(7): e40953.

DOI：10.1371/journal.pone.0040953

The precise neural mechanisms underlying speech sound representations are still a matter of debate. Proponents of %26apos;sparse representations%26apos; assume that on the level of speech sounds, only contrastive or otherwise not predictable information is stored in long-term memory. Here, in a passive oddball paradigm, we challenge the neural foundations of such a %26apos;sparse%26apos; representation; we use words that differ only in their penultimate consonant (%26quot;coronal%26quot; [t] vs. %26quot;dorsal%26quot; [k] place of articulation) and for example distinguish between the German nouns Latz ([lats]; bib) and Lachs ([laks]; salmon). Changes from standard [t] to deviant [k] and vice versa elicited a discernible Mismatch Negativity (MMN) response. Crucially, however, the MMN for the deviant [lats] was stronger than the MMN for the deviant [laks]. Source localization showed this difference to be due to enhanced brain activity in right superior temporal cortex. These findings reflect a difference in phonological %26apos;sparsity%26apos;: Coronal [t] segments, but not dorsal [k] segments, are based on more sparse representations and elicit less specific neural predictions; sensory deviations from this prediction are more readily %26apos;tolerated%26apos; and accordingly trigger weaker MMNs. The results foster the neurocomputational reality of %26apos;representationally sparse%26apos; models of speech perception that are compatible with more general predictive mechanisms in auditory perception.

• 出版日期2012-7-16