Biomedical subjects

Genevieve M McArthur

Publications and source records attributed to Genevieve M McArthur.

3 recordsLinked to original sources

PubMed2005

Is discrimination training necessary to cause changes in the P2 auditory event-related brain potential to speech sounds?

Previous studies have found that the P2 component of the auditory event-related potential (ERP) increases after speech discrimination training. We compared electrophysiological and behavioral outcomes of individuals undergoing speech discrimination training (N = 8) with an untrained control group (N = 9). Significant improvements on the behavioral speech discrimination task were found only in the trained group; however, there were similar increases in P2 amplitude in both groups. Simple exposure to repeated instances of a speech sound during the ERP recording seems sufficient lead to enhancement of P2. This interpretation was bolstered by the finding of significant change in P2 during the first and second halves of the initial ERP recording, when listeners were not required to make any discriminative response. However, the largest change in P2 occurred between rather than within recording sessions, suggesting that the effects of exposure to a speech stimulus on ERPs may have a slow time-course and are most evident after a delay. Our data challenge the view that increased P2 amplitude reflects enhanced perceptual discrimination by auditory cortex.

Acoustic Stimulation↗

PubMed2005

Individual differences in auditory processing in specific language impairment: a follow-up study using event-related potentials and behavioural thresholds.

It has frequently been claimed that children with specific language impairment (SLI) have impaired auditory perception, but there is much controversy about the role of such deficits in causing their language problems, and it has been difficult to establish solid, replicable findings in this area. Discrepancies in this field may arise because (a) a focus on mean results obscures the heterogeneity in the population and (b) insufficient attention has been paid to maturational aspects of auditory processing. We conducted a study of 16 young people with specific language impairment (SLI) and 16 control participants, 24 of whom had had auditory event-related potentials (ERPs) and frequency discrimination thresholds assessed 18 months previously. When originally assessed, around one third of the listeners with SLI had poor behavioural frequency discrimination thresholds, and these tended to be the younger participants. However, most of the SLI group had age-inappropriate late components of the auditory ERP, regardless of their frequency discrimination. At follow-up, the behavioural thresholds of those with poor frequency discrimination improved, though some remained outside the control range. At follow-up, ERPs for many of the individuals in the SLI group were still not age-appropriate. In several cases, waveforms of individuals in the SLI group resembled those of younger typically-developing children, though in other cases the waveform was unlike that of control cases at any age. Electrophysiological methods may reveal underlying immaturity or other abnormality of auditory processing even when behavioural thresholds look normal. This study emphasises the variability seen in SLI, and the importance of studying individual cases rather than focusing on group means.

Adolescent↗

PubMed2004

Phonological categorization of vowels: a mismatch negativity study.

There is electrophysiological evidence that phonological categorization has occurred within 100-200 ms post stimulus onset for the syllables /tae/ and /dae/, which vary in voice onset time. Using a similar paradigm, this study investigated when phonological categorization occurred for the contrast between /I/ and /epsilon/, using synthesized speech tokens that differed in the frequency of the first formant. Here we show that phonological categorization of these tokens has not occurred 100-200 ms after stimulus onset. However, the presence of a late mismatch negativity (350 ms after stimulus onset) indicated that phonological categorization had taken place by this time.

Acoustic Stimulation↗