Neural Correlates of Auditory Cognition by Yale E. Cohen Arthur N. Popper & Richard R. Fay

Author:Yale E. Cohen, Arthur N. Popper & Richard R. Fay
Language: eng
Format: epub
Publisher: Springer New York, New York, NY

Expanded windows of integration may have profound ramifications for the development of normal speech processing. This proposal is exemplified by the seminal finding of Tallal and colleagues, who found that a subgroup of children with specific language impairment (SLI) had difficulty in the differential perception of stop consonants containing rapid formant transitions (e.g., 40 ms), but performed at control levels when the formant transitions were extended to 80 ms (see Tallal et al., 1993). This observation helped lead to the development of the temporal processing hypothesis, which posits that deficits in auditory temporal processing are causally related to SLI. This highly contentious hypothesis has been supported by replication of the original results (see Burlingame et al., 2005 for review), and has been expanded to include deficits in many nonlinguistic auditory perceptions and in some individuals with dyslexia (e.g., Wright et al., 1997; Hari and Renvall, 2001; Vandermosten et al., 2010). A recent interpretation of the auditory temporal processing deficit hypothesis posits that the underlying abnormality is based on the use of expanded temporal windows of integration, resulting in degraded representation of phonemic fine-grained patterns and subsequent phonological dysfunction (Tallal, 2004).

Neural activity within A1 is degraded at longer windows of integration in a manner that parallels the perceptual findings of Tallal and colleagues. Steinschneider and Fishman (2011) recorded from A1 of awake monkeys while presenting the consonant–vowel (CV) syllables /ba/, /ga/, /da/ identical to the syllables shown in Fig. 6.2a, but with F2 and F3 transition durations that varied in 20-ms steps (20, 40, 60, and 80 ms). They ranked response amplitudes of MUA evoked by each syllable based on the relative amplitudes of the responses evoked by 800-, 1600-, and 3000-Hz tones. These tones were centered at the maxima of the initial consonant spectrum preceding the formant transitions. Comparisons were made at multiple physiological windows of integration ranging from 10–30 ms after stimulus onset to 10–110 ms in 20-ms expansion increments. When short windows of integration were used (e.g., 20 ms), there was accurate concordance between the tone-evoked and the syllable-evoked activity for all four sets of formant transition duration stimuli. However, as windows of integration were progressively increased, there was a corresponding decrease in the concordance between the tone-evoked and speech-evoked activity for the syllables with rapid formant transitions. By an integration window of 90 ms, concordance was observed only for the syllables with the longest formant transitions.

At short windows of integration, syllables containing both rapid and prolonged formant transitions can be discriminated accurately. However, if an individual “chunks” time in abnormally long integration windows, then only syllables with extended formant transition durations will be discriminated accurately. Expanded windows of integration are also compatible with other proposed acoustically based abnormalities in dyslexia (see Goswami et al., 2011) or those suggesting that attention mechanisms are dysfunctional based on “sluggish” attentional switching (Hari & Renvall, 2001). Further, it is possible that remediation therapies for SLI are effective in part by sharpening abnormally long integration windows (e.g., Tallal, 2004; Gillam et al., 2008).

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