Roger J. Wales’s research while affiliated with La Trobe University and other places

The aim of this study was to model the components of rhythmic function in a case (H.J.) of acquired rhythmic disturbance. H.J. is a right-handed, amateur male musician who acquired arrhythmia in the context of a global amusia after sustaining a right temporoparietal infarct. His rhythmic disturbance was analysed in relation to three independent components using an autoregressive extension of Wing and Kristofferson's model of rhythmic timing. This revealed preserved error-correction and motor implementation capacities, but a gross disturbance of H.J.'s central timing system ("cognitive clock"). It rendered him unable to generate a steady pulse, prevented adequate discrimination and reproduction of novel metrical rhythms, and partly contributed to bi-manual co-ordination difficulties in his instrumental performance. The findings are considered in relation to the essential components of the cognitive architecture of rhythmic function, and their respective cerebral lateralisation and localisation. Overall, the data suggested that the functioning of the right temporal auditory cortex is fundamental to 'keeping the beat' in music. The approach is presented as a new paradigm for future neuropsychological research examining rhythmic disturbances.

Cochlear implants have raised questions about how children with profoundly impaired hearing can learn spoken language. This study addresses the question of whether there is a critical level of hearing for the development of adequate speech perception abilities. A comparison of the relationships between speech perception scores and spoken language scores shows that a group of profoundly deaf children using hearing aids process spoken language in a way that is fundamentally different from two groups of children with severe and moderate hearing losses. We infer that there is a critical level of hearing below which speech perception relies very heavily on linguistic processing to compensate for limited auditory information. We also show that a cochlear implant can promote profoundly deaf children from below to above the critical level of hearing.

Conversational speech samples were analysed over a six-year period postoperatively for nine profoundly deaf children implanted with the Cochlear Limited 22-electrode cochlear implant between ages 2-5 years. Four years post-implant, at least 90% of all syllables produced by each child were intelligible, although only one of the children (who had suffered a progressive hearing loss) had over 10% intelligible syllables prior to implantation. Over the 6-year period, the mean number of intelligible words per utterance increased from 0.15 to 4.2 and the mean number of syllables (counting both intelligible and unintelligible syllables) increased from 1.7 to 5.2, indicating an increase in complexity as well as intelligibility. The speech samples were transcribed phonetically and percentage correct analyses were conducted on the transcripts. These analyses showed a steady improvement in the percentage of correctly produced monophthongs, diphthongs and consonants. There was a corresponding rise in the percentage of words that were produced without phonetic errors. Following six years of implantation, the speech acquisition process was incomplete, although there was no evidence to suggest a plateau in performance.

Eighty-seven primary-school children with impaired hearing were evaluated using speech perception, production, and language measures over a 3-year period. Forty-seven children with a mean unaided pure-tone-average hearing loss of 106 dB HL used a 22-electrode cochlear implant, and 40 with a mean unaided puretone-average hearing loss of 78 dB HL were fitted with hearing aids. All children were enrolled in oral/aural habilitation programs, and most attended integrated classes with normally hearing children for part of the time at school. Multiple linear regression was used to describe the relationships among the speech perception, production, and language measures, and the trends over time. Little difference in the level of performance and trends was found for the two groups of children, so the perceptual effect of the implant is equivalent, on average, to an improvement of about 28 dB in hearing thresholds. Scores on the Peabody Picture Vocabulary Test (PPVT) and the Clinical Evaluation of Language Fundamentals showed an upward trend at about 60% of the rate for normally hearing children. Rates of improvement for individual children were not correlated significantly with degree of hearing loss. The children showed a wide scatter about the average speech production score of 40% of words correctly produced in spontaneous conversations, with no significant upward trend with age. Scores on the open-set Consonant-Nucleus-Consonant (CNC) monosyllabic word test and the Bench-Kowal-Bamford (BKB) sentence test were strongly related to language level (as measured by an equivalent age on the PPVT) and speech production scores for both auditory-visual and auditory test conditions. After allowing for differences in language, speech perception scores in the auditory test condition showed a slight downward trend over time, which is consistent with the known biological effects of hearing loss on the auditory periphery and brainstem. Speech perception scores in the auditory condition also decreased significantly by about 5% for every 10 dB of hearing loss in the hearing aid group. The regression analysis model allows separation of the effects of language, speech production, and hearing levels on speech perception scores so that the effects of habilitation and training in these areas can be observed and/or predicted. The model suggests that most of the children in the study will reach a level of over 90% sentence recognition in the auditory-visual condition when their language becomes equivalent to that of a normally hearing 7-year-old, but they will enter secondary school at age 12 with an average language delay of about 4 or 5 years unless they receive concentrated and effective language training.

Individuals with schizophrenia experience problems in the perception of emotional material; however, the specificity, extent, and nature of the deficits are unclear. Facial affect and affective prosody recognition were examined in representative samples of individuals with first-episode psychosis, assessed as outpatients during the early recovery phase of illness, and non-patients. Perception tasks were selected to allow examination of emotion category results across face and voice modalities. Facial tasks were computerised modifications of the Feinberg et al. procedure (Feinberg, T.E., Rifkin, A., Schaffer, C., Walker, E., 1986. Arch. Gen. Psychiatry 43, 276--279). Prosody tasks were developed using four professional actors, and item selections were based on responses of undergraduates. Participant groups did not differ in their understanding of the words used to describe emotions. Findings supported small but consistent deficits in recognition of fear and sadness across both communication channels for the combined schizophrenia (n=29) and other psychotic disorders (n=28) groups as compared to the affective psychoses (n=23) and non-patients (n=24). A diagnostic effect was evident that was independent of the contribution of intelligence. The detection of emotion recognition impairments in first-episode schizophrenia suggests a trait deficit. The pattern of results is consistent with amygdala dysfunction in schizophrenia and related psychoses.

In this study, a computer-based musical composition task was used to access higher order musical representations of adult nonmusicians, and patients having undergone left- or right-sided anterior temporal lobectomy (ATL). Compositions were rated according to the main features of cognitive structuralist models of pitch, tonality, rhythm, and phrase structure (musical grouping), as well as in terms of their nontonal complexity. The results showed that all participants created compositions that contained features typical of Western tonal music. The a priori music-theoretical structure of the cognitive models, however, was not reflected in the data. Laterality effects were observed for the left and right ATL patients in comparison to the adult nonmusicians. Left ATL patients showed less use of tonal features in their compositions, whilst right ATL patients placed less emphasis on phrase structure and melodic contour. The right ATL patients also showed impaired melodic discrimination in comparison to the normal controls.

The aim of this study was to explore the development of the representations of tonality and meter in children. Eighty children with a mean age of 7 (Grade 2) and 9 years (Grade 4) were compared on both melodic and rhythmic discrimination and classification tasks. The findings were considered in relation to their specificity to both task and age effects. The results revealed a developmental progression in the representation of tonality that was consistent across tasks. The rhythmic results also supported the existence of a representation of meter that developed with age, however these findings were more subject to task effects. The influence of stimulus length and likeableness on subject performance was also examined. Increased length was found to assist discrimination performance particularly with tonal, nontonal, and nonmetrical stimuli. No effects of stimulus likeableness were observed in the data.