Making Sense of Sentences: Top-Down Processing of Speech by Adult Cochlear Implant Users

Abstract

Purpose: Speech recognition relies upon a listener's successful pairing of the acoustic-phonetic details from the bottom-up input with top-down linguistic processing of the incoming speech stream. When the speech is spectrally degraded, such as through a cochlear implant (CI), this role of top-down processing is poorly understood. This study explored the interactions of top-down processing, specifically the use of semantic context during sentence recognition, and the relative contributions of different neurocognitive functions during speech recognition in adult CI users. Method: Data from 41 experienced adult CI users were collected and used in analyses. Participants were tested for recognition and immediate repetition of speech materials in the clear. They were asked to repeat 2 sets of sentence materials, 1 that was semantically meaningful and 1 that was syntactically appropriate but semantically anomalous. Participants also were tested on 4 visual measures of neurocognitive functioning to assess working memory capacity (Digit Span; Wechsler, 2004), speed of lexical access (Test of Word Reading Efficiency; Torgeson, Wagner, & Rashotte, 1999), inhibitory control (Stroop; Stroop, 1935), and nonverbal fluid reasoning (Raven's Progressive Matrices; Raven, 2000). Results: Individual listeners' inhibitory control predicted recognition of meaningful sentences when controlling for performance on anomalous sentences, our proxy for the quality of the bottom-up input. Additionally, speed of lexical access and nonverbal reasoning predicted recognition of anomalous sentences. Conclusions: Findings from this study identified inhibitory control as a potential mechanism at work when listeners make use of semantic context during sentence recognition. Moreover, speed of lexical access and nonverbal reasoning were associated with recognition of sentences that lacked semantic context. These results motivate the development of improved comprehensive rehabilitative approaches for adult patients with CIs to optimize use of top-down processing and underlying core neurocognitive functions. Bottom-Up Processing of the Signal and Top-Down Use of Context Speech recognition is an interactive process between the incoming acoustic-phonetic features of the auditory

Speech Recognition as a Function of Age and Listening Experience in Adult Cochlear Implant Users

“…As temporal processing abilities decline with advanced age, 38 older adults may experience more difficulty in discriminating a distorted speech signal 39 . Additionally, physiologic changes in neurocognitive function such as working memory capacity, nonverbal reasoning, and inhibitory control likely affect speech recognition in older adults 40–42 . These central factors can manifest in older listeners as greater difficulty ignoring competing noise while attending to target speech, particularly when the masker consists of competing talkers 43,44 .…”

“…39 Additionally, physiologic changes in neurocognitive function such as working memory capacity, nonverbal reasoning, and inhibitory control likely affect speech recognition in older adults. [40][41][42] These central factors can manifest in older listeners as greater difficulty ignoring competing noise while attending to target speech, particularly when the masker consists of competing talkers. 43,44 Age-related reductions in neurocognition could explain why age effects are not always observed when test materials are presented in quiet.…”

A Novel Performance‐Based Paradigm of Care for Cochlear Implant Follow‐Up

“…The other assessment tools in the MSTB use recorded sentences, which introduce contextual knowledge, working memory, and cognition into test performance. 24,25 These cognitive skills, known as top-down processing, are utilized by CI users to accommodate for the highly degraded, acoustic-phonetic, bottom-up representation of speech. 26 Therefore, the CNC word list was used as a more pure measure of CI performance without incorporating measures of top-down processing.…”

A surgeon‐scientist's perspective and review of cognitive‐linguistic contributions to adult cochlear implant outcomes

“…Quicker correct responses suggest better inhibition‐concentration. Using this task, we have found correlations with several different measures of sentence recognition, and the ability to use sentence context, in speech‐shaped noise and/or in quiet 31,32 …”