Low-level Auditory Processing Research Articles

Speech perception in preschoolers at family risk for dyslexia: Relations with low-level auditory processing and phonological ability

We tested categorical perception and speech-in-noise perception in a group of five-year-old preschool children genetically at risk for dyslexia, compared to a group of well-matched control children and a group of adults. Both groups of children differed significantly from the adults on all speech measures. Comparing both child groups, the risk group presented a slight but significant deficit in speech-in-noise perception, particularly in the most difficult listening condition. For categorical perception a marginally significant deficit was observed on the discrimination task but not on the identification task. Speech parameters were significantly related to phonological awareness and low-level auditory measures. Results are discussed within the framework of a causal model where low-level auditory problems are hypothesized to result in subtle speech perception problems that might interfere with the development of phonology and reading and spelling ability.

Auditory processing skills and phonological representation in dyslexic children.

It is now well-established that there is a causal connection between children's phonological skills and their acquisition of reading and spelling. Here we study low-level auditory processes that may underpin the development of phonological representations in children. Dyslexic and control children were given a battery of phonological tasks, reading and spelling tasks and auditory processing tasks. Potential relations between deficits in dyslexic performance in the auditory processing tasks and phonological awareness were explored. It was found that individual differences in auditory tasks requiring amplitude envelope rise time processing explained significant variance in phonological processing. It is argued that developmentally, amplitude envelope cues may be primary in establishing well-specified phonological representations, as these cues should yield important rhythmic and syllable-level information about speech.

Receptive amusia: temporal auditory processing deficit in a professional musician following a left temporo-parietal lesion

This study examined the musical processing in a professional musician who suffered from amusia after a left temporo-parietal stroke. The patient showed preserved metric judgement and normal performance in all aspects of melodic processing. By contrast, he lost the ability to discriminate or reproduce rhythms. Arrhythmia was only observed in the auditory modality: discrimination of auditorily presented rhythms was severely impaired, whereas performance was normal in the visual modality. Moreover, a length effect was observed in discrimination of rhythm, while this was not the case for melody discrimination. The arrhythmia could not be explained by low-level auditory processing impairments such as interval and length discrimination and the impairment was limited to auditory input, since the patient produced correct rhythmic patterns from a musical score. Since rhythm processing was selectively disturbed in the auditory modality, the arrhythmia cannot be attributed to a impairment of supra-modal temporal processing. Rather, our findings suggest modality-specific encoding of musical temporal information. Besides, it is proposed that the processing of auditory rhythmic sequences involves a specific left hemispheric temporal buffer.

Auditory processing deficits in reading disabled adults.

The nature of the auditory processing deficit of disabled readers is still an unresolved issue. The quest for a fundamental, nonlinguistic, perceptual impairment has been dominated by the hypothesis that the difficulty lies in processing sequences of stimuli at presentation rates of tens of milliseconds. The present study examined this hypothesis using tasks that require processing of a wide range of stimulus time constants. About a third of the sampled population of disabled readers (classified as "poor auditory processors") had difficulties in most of the tasks tested: detection of frequency differences, detection of tones in narrowband noise, detection of amplitude modulation, detection of the direction of sound sources moving in virtual space, and perception of the lateralized position of tones based on their interaural phase differences. Nevertheless, across-channel integration was intact in these poor auditory processors since comodulation masking release was not reduced. Furthermore, phase locking was presumably intact since binaural masking level differences were normal. In a further examination of temporal processing, participants were asked to discriminate two tones at various intervals where the frequency difference was ten times each individual's frequency just noticeable difference (JND). Under these conditions, poor auditory processors showed no specific difficulty at brief intervals, contrary to predictions under a fast temporal processing deficit assumption. The complementary subgroup of disabled readers who were not poor auditory processors showed some difficulty in this condition when compared with their direct controls. However, they had no difficulty on auditory tasks such as amplitude modulation detection, which presumably taps processing of similar time scales. These two subgroups of disabled readers had similar reading performance but those with a generally poor auditory performance scored lower on some cognitive tests. Taken together, these results suggest that a large portion of disabled readers suffer from diverse difficulties in auditory processing. No parsimonious explanation based on current models of low-level auditory processing can account simultaneously for all these results, though increased within-channel noise is consistent with the majority of the deficits found in the subgroup of poorer auditory processors.

Mapping theories of developmental language impairment: Premises, predictions and evidence

This paper presents the case for a mapping theory of developmental language impairment, which branches into a theory that Specific Language Impairment (SLI) arises from impaired phonological processing and the consequent disruption of the mapping process through which the words and sentence structure of a language are established. The prelude to the case is that the mapping process, which is a sine qua non of language acquisition, is the first place to look for possible sources of deficits in language acquisition; that recent research on the mapping process points up the contribution of complex phonological processing not just in the segmentation and representation of lexical phonology, but in wider lexical and syntactic development; and that phonological processing is therefore a plausible source of the deficits observed in SLI. Detailed analysis of the mapping process and the role of phonological processing gives rise to specific predictions which are evaluated against wide-ranging research findings on children with SLI. It is argued that the phonological theory provides a better fit with this empirical evidence than theories which posit either specific grammatical deficits or low-level auditory processing deficits, and offers more far-reaching insights than theories which invoke a general limitation in processing capacity. The paper concludes with wider implications, further predictions, and further questions arising from the mapping theory of developmental language impairment and its particular instantiation in the phonological theory of SLI.

Is the sine-wave speech cocktail party worth attending?

Listeners are remarkably adept at recognising speech that has undergone extensive spectral reduction. Natural speech can be reproduced using as few as three time-varying sinusoids mimicking the corresponding speech formants. Untrained listeners are able to transcribe this `sine-wave' speech with a high degree of reliability. Coherent phonetic percepts generated by sine-wave speech occur despite an apparent lack of those cues on which low level auditory grouping processes are believed to operate. Consequently, it has been proposed that speech perception is governed by processes operating independently of those described by auditory scene analysis. This paper re-examines the evidence provided by previous perceptual studies of sine-wave speech and presents new data, from perceptual studies employing stimuli constructed from simultaneous sine-wave wave speech sources. These new studies suggest that in conditions that are closer to those of everyday listening, grouping cues have an important role in the formation of coherent speech percepts. In conjunction with these perceptual studies, results from automatic segregation and recognition tasks suggest that sine-wave speech contains sufficient low level, non speech-specific, structure to allow partial descriptions of sine-wave sources to be recovered from two-source mixtures. It is argued that these partial descriptions may be sufficient to account for the limited intelligibility observed in two-source sine-wave speech listening tests.

Computational modelling of auditory streaming phenomena

A computer model is described that uses simple physiological principles that operate mainly at a peripheral level to account for perceptual coherence among successive pure tones of changing frequency. Using a single set of parameter values, the model is able to reproduce a number of fundamental auditory streaming phenomena. These include the build-up of auditory stream segregation over time, and the temporal coherence and fission boundaries of human listeners. Whereas these streaming phenomena are generally accounted for in terms of a high-level auditory scene-analysis process, the success of the model in reproducing experimental data obtained from humans justifies the potential value of a low-level analysis for explaining auditory grouping phenomena, and suggests that some auditory grouping may be the product of low-level auditory processing

Low-level sensory processing in obsessive-compulsive disorder: An evoked potential study

This study used visual and auditory evoked potentials (VEP and AEP) to study low-level sensory processing in a group of 15 unmediated subjects with obsessive-compulsive disorder (OCD) and 30 age-matched, gender-matched, and handedness-matched normal controls. EPs were recorded to flash (VEP) and binaural click (AEP) stimulation. OCD subjects were found to have significantly shorter latencies on N1 and P2 of the AEP, and no differences were found in the VEP. Results indicate abnormal information processing states in OCD during low-level auditory processing, but not during low-level visual processing. Neural generators of the VEP and AEP are briefly reviewed and results are discussed in relation to current neurobiological models of OCD.

A computer implementation of psychoacoustic grouping rules

Many of the rules employed by the human auditory system to fuse and segregate acoustic energy into separately perceived sources are described by Bregman [A. S. Bregman, AuditorySceneAnalysis (MIT, Cambridge, MA, 1990)]. However, the precise application of these rules to anything but the most simple experimental stimuli is less well understood. This idealized model of low-level auditory processing [Ellis and Vercoe, J. Acoust. Soc. Am. 91, 2334 (A) (1992)]; [Ellis, J. Acoust. Soc. Am. 92, 2376 (A) (1992)] is specifically designed to facilitate automatic grouping for real stimuli. This is achieved by representing sounds as sets of sinusoid tracks, the discrete time-frequency elements required by such rules. This system is discussed for grouping tracks, and it is shown that the results are obtained by applying simple rules for harmonicity, common fate, and proximity to some real sounds. The means by which ambiguity has been resolved between different types of rule, along with other issues arising from the model, will also be described.

Computer simulation of auditory stream segregation in sequential-tone sequences

A simple computer model is described that takes a novel approach to the problem of accounting for perceptual coherence among successive pure tones of changing frequency by using simple physiological principles that operate mainly at a peripheral, rather than a central level. Using a single set of parameter values, the model is able to reproduce a number of streaming phenomena found in the literature. These are: (1) the buildup of auditory streaming over time, (2) the temporal coherence and fission boundaries of human listeners, (3) the trill threshold, and (4) the stream-organization process exhibited by human listeners when presented with ABC tone sequences. Whereas streaming phenomena are generally accounted for in terms of an auditory scene-analysis process that works on the basis of Gestalt perceptual principles, the success of the model in reproducing experimental data obtained from humans justifies the potential value of a low-level analysis for explaining high-level psychological phenomena such as Gestalt auditory grouping, and suggests that some Gestalt auditory grouping may be the product of low-level auditory processing. [Work supported by SERC(UK) and CNRS(France).]

Virtual pitch and phase sensitivity of a computer model of the auditory periphery. II: Phase sensitivity

In a companion article [Meddis and Hewitt, J. Acoust. Soc. Am. 89, 2866–2882 (1991)] it was shown that a computational model of the auditory periphery followed by a system of autocorrelation analyses was able to account for a wide range of human virtual pitch perception phenomena. In this article it is shown that the same model, with no substantial modification, can predict a number of results concerning human sensitivity to phase relationships among harmonic components of tone complexes. The model is successfully evaluated using (a) amplitude-modulated and quasifrequency-modulated stimuli, (b) harmonic complexes with alternating phase change and monotonic phase change across harmonic components, and (c) mistuned harmonics. The model is contrasted with phase-insensitive theories of low-level auditory processing and offered as further evidence in favor of the value of analysing time intervals among spikes in the auditory nerve when explaining psychophysical phenomena.