Learning in a task of complex auditory streaming and identification

Learning effects in speech-in-noise tasks: Effect of masker modulation and masking release

Previous research has shown that learning effects are present for speech intelligibility in temporally modulated (TM) noise, but not in stationary noise. The present study aimed to gain more insight into the factors that might affect the time course (the number of trials required to reach stable performance) and size [the improvement in the speech reception threshold (SRT)] of the learning effect. Two hypotheses were addressed: (1) learning effects are present in both TM and spectrally modulated (SM) noise and (2) the time course and size of the learning effect depend on the amount of masking release caused by either TM or SM noise. Eighteen normal-hearing adults (23-62 years) participated in SRT measurements, in which they listened to sentences in six masker conditions, including stationary, TM, and SM noise conditions. The results showed learning effects in all TM and SM noise conditions, but not for the stationary noise condition. The learning effect was related to the size of masking release: a larger masking release was accompanied by an increased time course of the learning effect and a larger learning effect. The results also indicate that speech is processed differently in SM noise than in TM noise.

Speech Discrimination Tasks: A Sensitive Sensory and Cognitive Measure in Early and Mild Multiple Sclerosis

There is a need for reliable and objective measures of early and mild symptomology in multiple sclerosis (MS), as deficits can be subtle and difficult to quantify objectively in patients without overt physical deficits. We hypothesized that a speech-in-noise (SiN) task would be sensitive to demyelinating effects on precise neural timing and diffuse higher-level networks required for speech intelligibility, and therefore be a useful tool for monitoring sensory and cognitive changes in early MS. The objective of this study was to develop a SiN task for clinical use that sensitively monitors disease activity in early (<5 years) and late (>10 years) stages of MS subjects with mild severity [Expanded Disability Status Scale (EDSS) score < 3]. Pre-recorded Bamford-Kowal-Bench sentences and isolated keywords were presented at five signal-to-noise ratios (SNR) in one of two background noises: speech-weighted noise and eight-talker babble. All speech and noise were presented via headphones to controls (n = 38), early MS (n = 23), and late MS (n = 12) who were required to verbally repeat the target speech. MS subjects also completed extensive neuropsychological testing which included: Paced Auditory Serial Addition Test, Digit Span Test, and California Verbal Learning Test. Despite normal hearing thresholds, subjects with early and late mild MS displayed speech discrimination deficits when sentences and words were presented in babble - but not speech-weighted noise. Significant correlations between SiN performance and standardized neuropsychological assessments indicated that MS subjects with lower functional scores also had poorer speech discrimination. Furthermore, a quick 5-min task with words and keywords presented in multi-talker babble at an SNR of -1 dB was 82% accurate in discriminating mildly impaired MS individuals (median EDSS = 0) from healthy controls. Quantifying functional deficits in mild MS will help clinicians to maximize the opportunities to preserve neurological reserve in patients with appropriate therapeutic management, particularly in the earliest stages. Given that physical assessments are not informative in this fully ambulatory cohort, a quick 5-min task with words and keywords presented in multi-talker babble at a single SNR could serve as a complementary test for clinical use due to its ease of use and speed.

The long-term learning effect related to the repeated use of the Finnish matrix sentence test and the Finnish digit triplet test

Objectives: To assess are there learning-related improvements in the speech reception thresholds (SRTs) for the Finnish matrix sentence test (FMST) and the Finnish digit triplet test (FDTT) in repeated use over 12 months.Design: Test sessions were scheduled at 0, 1, 3, 6 and 12 months, and each session included five FMST measurements and four FDTT measurements. The within-session and inter-session improvements in SRTs were analysed with a linear mixed model.Study sample: Fifteen young normal-hearing participants.Results: Statistically significant mean improvements of 2.0 dB SNR and 1.2 dB SNR were detected for the FMST and the FDTT, respectively, over the 12-month follow-up period. For the FMST, majority of the improvement occurred during the first two test sessions. For the FDTT, statistically significant differences were detected only in comparison to the first test session and to the first test measurement of every session over the 12-month follow-up.Conclusions: Repeated use of the FMST led to significant learning-related improvements, but the improvements appeared to plateau by the third test session. For the FDTT, the overall improvements were smaller, but a significant within-session difference between the first and consecutive FDTT measurements persisted throughout the test sessions.

Speech Discrimination Difficulties in High-Functioning Autism Spectrum Disorder Are Likely Independent of Auditory Hypersensitivity

Autism Spectrum Disorder (ASD), characterized by impaired communication skills and repetitive behaviors, can also result in differences in sensory perception. Individuals with ASD often perform normally in simple auditory tasks but poorly compared to typically developed (TD) individuals on complex auditory tasks like discriminating speech from complex background noise. A common trait of individuals with ASD is hypersensitivity to auditory stimulation. No studies to our knowledge consider whether hypersensitivity to sounds is related to differences in speech-in-noise discrimination. We provide novel evidence that individuals with high-functioning ASD show poor performance compared to TD individuals in a speech-in-noise discrimination task with an attentionally demanding background noise, but not in a purely energetic noise. Further, we demonstrate in our small sample that speech-hypersensitivity does not appear to predict performance in the speech-in-noise task. The findings support the argument that an attentional deficit, rather than a perceptual deficit, affects the ability of individuals with ASD to discriminate speech from background noise. Finally, we piloted a novel questionnaire that measures difficulty hearing in noisy environments, and sensitivity to non-verbal and verbal sounds. Psychometric analysis using 128 TD participants provided novel evidence for a difference in sensitivity to non-verbal and verbal sounds, and these findings were reinforced by participants with ASD who also completed the questionnaire. The study was limited by a small and high-functioning sample of participants with ASD. Future work could test larger sample sizes and include lower-functioning ASD participants.

Poorer verbal working memory for a second language selectively impacts academic achievement in university medical students

Working memory (WM) is often poorer for a second language (L2). In low noise conditions, people listening to a language other than their first language (L1) may have similar auditory perception skills for that L2 as native listeners, but do worse in high noise conditions, and this has been attributed to the poorer WM for L2. Given that WM is critical for academic success in children and young adults, these speech in noise effects have implications for academic performance where the language of instruction is L2 for a student. We used a well-established Speech-in-Noise task as a verbal WM (vWM) test, and developed a model correlating vWM and measures of English proficiency and/or usage to scholastic outcomes in a multi-faceted assessment medical education program. Significant differences in Speech-Noise Ratio (SNR₅₀) values were observed between medical undergraduates who had learned English before or after five years of age, with the latter group doing worse in the ability to extract whole connected speech in the presence of background multi-talker babble (Student-t tests, p < 0.001). Significant negative correlations were observed between the SNR₅₀ and seven of the nine variables of English usage, learning styles, stress, and musical abilities in a questionnaire administered to the students previously. The remaining two variables, Perceived Stress Scale (PSS) and the Age of Acquisition of English (AoAoE) were significantly positively correlated with the SNR₅₀, showing that those with a poorer capacity to discriminate simple English sentences from noise had learnt English later in life and had higher levels of stress – all characteristics of the international students. Local students exhibited significantly lower SNR₅₀ scores and were significantly younger when they first learnt English. No significant correlation was detected between the SNR₅₀ and the students’ Visual/Verbal Learning Style (r = −0.023). Standard multiple regression was carried out to assess the relationship between language proficiency and verbal working memory (SNR₅₀) using 5 variables of L2 proficiency, with the results showing that the variance in SNR₅₀ was significantly predicted by this model (r² = 0.335). Hierarchical multiple regression was then used to test the ability of three independent variable measures (SNR₅₀, age of acquisition of English and English proficiency) to predict academic performance as the dependent variable in a factor analysis model which predicted significant performance differences in an assessment requiring communications skills (p = 0.008), but not on a companion assessment requiring knowledge of procedural skills, or other assessments requiring factual knowledge. Thus, impaired vWM for an L2 appears to affect specific communications-based assessments in university medical students.