Role of working memory and lexical knowledge in perceptual restoration of interrupted speech

Abstract

The role of working memory (WM) capacity and lexical knowledge in perceptual restoration (PR) of missing speech was investigated using the interrupted speech perception paradigm. Speech identification ability, which indexed PR, was measured using low-context sentences periodically interrupted at 1.5 Hz. PR was measured for silent gated, low-frequency speech noise filled, and low-frequency fine-structure and envelope filled interrupted conditions. WM capacity was measured using verbal and visuospatial span tasks. Lexical knowledge was assessed using both receptive vocabulary and meaning from context tests. Results showed that PR was better for speech noise filled condition than other conditions tested. Both receptive vocabulary and verbal WM capacity explained unique variance in PR for the speech noise filled condition, but were unrelated to performance in the silent gated condition. It was only receptive vocabulary that uniquely predicted PR for fine-structure and envelope filled conditions. These findings suggest that the contribution of lexical knowledge and verbal WM during PR depends crucially on the information content that replaced the silent intervals. When perceptual continuity was partially restored by filler speech noise, both lexical knowledge and verbal WM capacity facilitated PR. Importantly, for fine-structure and envelope filled interrupted conditions, lexical knowledge was crucial for PR.

Relationship between Speech Perception in Noise and Phonemic Restoration of Speech in Noise in Individuals with Normal Hearing

“…A similar pattern was also reported by Bhargava and colleagues [6] as well. Direct comparison of the magnitude of phonemic restoration obtained in the present study vis-a-vis other studies is difficult since we preferred to use the raw scores instead of the typical rationalized arcsine unit (RAU) transformation [6,8] or percentages [11,25]. Since the datapoints were already normally distributed without large skews, we preferred this over other transformations to preserve the actual/natural distribution of speech scores.…”

“…They suggest that older individuals tend to have poorer access to bottom-up cues and maybe more dependent on top-down processing, resulting in a larger phonemic restoration. Variations in working memory abilities and linguistic proficiency [7,12,25] among the subjects could also contribute to the variance in the magnitude of restoration. The reason for this intelligibility increase with noise interruption over silent interruption is likely multi-faceted.…”

“…As such, there can be no doubt that it involves a complex interaction of bottom-up and top-down mechanisms in an effort to make sense of what is being heard. Phonemic restoration is a top-down effect based on the perception of illusory continuity of speech and grouping of speech and noise into separate streams, leading to a better access of lexical candidates [2,4,6,10,11,25]. So, it is possible that mechanisms serving phonemic restoration may well be at least partially involved in speech in noise perception as well and hence, the observed correlation.…”

“…However, the explanation maybe simpler. Verbal working memory (like speech in noise) has been reported to be associated with phonemic restoration only when the interruptions were with speech noise, but not with other types of noise [25]. It is thus possible that top-down mechanisms are better activated when evidences of gaps are masked more efficiently (for example, with a more intense noise).…”

Auditory processing in children: Role of working memory and lexical ability in auditory closure

“…Studies in adults suggest that vocabulary, and acoustic and phonological processing influence auditory closure [ 12 , 13 ]. However, there are limited studies on school-age children’s auditory closure ability that also examine constraining cognitive-linguistic factors.…”