a sparse neural code for some speech sounds but not for others稀疏的神经编码语音而不是为别人.pdfVIP

A Sparse Neural Code for Some Speech Sounds but Not for Others 1 2 3 1 Mathias Scharinger *, Alexandra Bendixen , Nelson J. Trujillo-Barreto , Jonas Obleser 1 Max Planck Research Group ‘‘Auditory Cognition’’, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany, 2 Institute of Psychology, University of Leipzig, Leipzig, Germany, 3 Cuban Neuroscience Center, Havana, Cuba Abstract The precise neural mechanisms underlying speech sound representations are still a matter of debate. Proponents of ‘sparse representations’ 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 ‘sparse’ representation; we use words that differ only in their penultimate consonant (‘‘coronal’’ [t] vs. ‘‘dorsal’’ [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 ‘sparsity’: 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 ‘tolerated’ and accordingly trigger weaker MMNs. The results foster the neurocomputational reality of ‘rep