Genevieve McArthur

On the "specifics" of specific reading disability and specific language impairment.

The reading and oral language scores of 110 children with a specific reading disability (SRD) and 102 children with a specific language impairment (SLI) indicated that approximately 53% of children with an SRD and children with an SLI could be equally classified as having an SRD or an SLI, 55% of children with an SRD have impaired oral language, and 51% of children with an SLI have a reading disability. Finding that a large percentage of children can be equally classified as SRD or SLI has repercussions for the criteria used to define an SRD, for conceptualising subgroups of learning disability, and for estimates of the incidence of SRD. Further, it highlights the need for future studies to assess both the reading and oral language abilities of SRD and SLI participants to determine how specifically impaired and homogeneous samples really are.

WHICH PEOPLE WITH SPECIFIC LANGUAGE IMPAIRMENT HAVE AUDITORY PROCESSING DEFICITS

An influential theory attributes developmental disorders of language and literacy to low‐level auditory perceptual difficulties. However, evidence to date has been inconsistent and contradictory. We investigated whether this mixed picture could be explained in terms of heterogeneity in the language‐impaired population. In Experiment 1, the behavioural responses of 16 people with specific language impairment (SLI) and 16 control listeners (aged 10 to 19 years) to auditory backward recognition masking (ABRM) stimuli and unmasked tones indicated that a subgroup of people with SLI are less able to discriminate between the frequencies of sounds regardless of their rate of presentation. Further, these people tended to be the younger participants, and were characterised by relatively poor nonword reading. In Experiment 2, the auditory event‐related potentials (ERPs) of the same groups to unmasked tones were measured. Listeners with SLI tended to have age‐inappropriate waveforms in the N1‐P2‐N2 region, regardless of their auditory discrimination scores in Experiment 1. Together, these results suggest that SLI may be characterised by immature development of auditory cortex, such that adult‐level frequency discrimination performance is attained several years later than normal.

Validation of the Emotiv EPOC® EEG gaming system for measuring research quality auditory ERPs

Background. Auditory event-related potentials (ERPs) have proved useful in investigating the role of auditory processing in cognitive disorders such as developmental dyslexia, specific language impairment (SLI), attention deficit hyperactivity disorder (ADHD), schizophrenia, and autism. However, laboratory recordings of auditory ERPs can be lengthy, uncomfortable, or threatening for some participants – particularly children. Recently, a commercial gaming electroencephalography (EEG) system has been developed that is portable, inexpensive, and easy to set up. In this study we tested if auditory ERPs measured using a gaming EEG system (Emotiv EPOC®, www.emotiv.com) were equivalent to those measured by a widely-used, laboratory-based, research EEG system (Neuroscan). Methods. We simultaneously recorded EEGs with the research and gaming EEG systems, whilst presenting 21 adults with 566 standard (1000 Hz) and 100 deviant (1200 Hz) tones under passive (non-attended) and active (attended) conditions. The onset of each tone was marked in the EEGs using a parallel port pulse (Neuroscan) or a stimulus-generated electrical pulse injected into the O1 and O2 channels (Emotiv EPOC®). These markers were used to calculate research and gaming EEG system late auditory ERPs (P1, N1, P2, N2, and P3 peaks) and the mismatch negativity (MMN) in active and passive listening conditions for each participant. Results. Analyses were restricted to frontal sites as these are most commonly reported in auditory ERP research. Intra-class correlations (ICCs) indicated that the morphology of the research and gaming EEG system late auditory ERP waveforms were similar across all participants, but that the research and gaming EEG system MMN waveforms were only similar for participants with non-noisy MMN waveforms (N = 11 out of 21). Peak amplitude and latency measures revealed no significant differences between the size or the timing of the auditory P1, N1, P2, N2, P3, and MMN peaks. Conclusions. Our findings suggest that the gaming EEG system may prove a valid alternative to laboratory ERP systems for recording reliable late auditory ERPs (P1, N1, P2, N2, and the P3) over the frontal cortices. In the future, the gaming EEG system may also prove useful for measuring less reliable ERPs, such as the MMN, if the reliability of such ERPs can be boosted to the same level as late auditory ERPs.

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.

Speech and non-speech processing in people with specific language impairment: A behavioural and electrophysiological study

McArthur and Bishop (2004) found that people with specific language impairment (SLI) up to 14 years of age have poor behavioural frequency discrimination (FD) thresholds for 25-ms pure tones, while people with SLI upto 20 years of age have abnormal auditory N1--P2--N2 event-related potential (ERP) responses to the same tones. In the present study, we extended these findings to more complex non-speech and speech sounds by comparing younger (around 13 years) and older (around 17 years) teenagers with SLI and controls for their behavioural FD thresholds and N1-P2 ERPs to 25 and 250-ms pure tones, vowels, and non-harmonic complex tones. We found that a subgroup of people with SLI had abnormal responses to tones and vowels at the level of behaviour and the brain, and that poor processing was associated with the spectral complexity of auditory stimuli rather than their phonetic significance. We suggest that both the age of listeners and the sensitivity of psychoacoustic tasks to age-related changes in auditory skills may be crucial factors in studies of sound processing in SLI.

Auditory Processing Deficits in Children with Reading and Language Impairments: Can They (and Should They) Be Treated?.

Sixty-five children with specific reading disability (SRD), 25 children with specific language impairment (SLI), and 37 age-matched controls were tested for their frequency discrimination, rapid auditory processing, vowel discrimination, and consonant-vowel discrimination. Subgroups of children with SRD or SLI produced abnormal frequency discrimination (42%), rapid auditory processing (12%), vowel discrimination (23%), or consonant-vowel discrimination (18%) thresholds for their age. Twenty-eight of these children trained on a programme that targeted their specific auditory processing deficit for 6 weeks. Twenty-five of these 28 trainees produced normal thresholds for their targeted processing skill after training. These gains were not explained by gains in auditory attention, in the ability to do psychophysical tasks in general, or by test-retest effects. The 25 successful trainees also produced significantly higher scores on spoken language and spelling tests after training. However, an untrained control group showed test-retest effects on the same tests. These results suggest that auditory processing deficits can be treated successfully in children with SRD and SLI but that this does not help them acquire new reading, spelling, or spoken language skills.

Assessing the basic components of reading: A revision of the Castles and Coltheart test with new norms

We present administration details and normative data for a new version of the word and nonword reading test originally developed by Castles and Coltheart. The new test contains an expanded set of items, with 40 each of regular words, irregular words and nonwords, rather than the original 30 items of each type. The new items extend the upper-end of the difficulty range of the test, making it less susceptible to ceiling effects than the original version. The test also incorporates a stopping-rule, which makes administration of the test less time-consuming and removes the stress on children who can only read a few items. The test is free of charge and is available to teachers, professionals and researchers in both pencil-and-paper and computer-based formats from the Macquarie On-line Test Interface (MOTIF: http://www.maccs.mq.edu.au/research/resources).

The attentional blink and P300.

The attentional blink (AB) is a brief impairment of visual processing occurring 200-500 ms after a target in a rapid stream of visual stimuli. At issue here is the relationship between AB and the P300 ERP component, as both are maximal at about 300 ms and have been hypothesised to reflect inhibitory processes. Two experiments revealed that AB and P300 follow a similar time course at the individual and group level, that reducing task difficulty has similar effects on AB and P300 magnitude at the group level, but that there is no relationship between the magnitude of AB and P300 within observers. These findings suggest a moderate association between the two phenomena, which may mirror transient inhibition of cortical networks to facilitate processing of target events.

Do video sounds interfere with auditory event-related potentials?

To make the electroencephalogram (EEG) recording procedure more tolerable, listeners have been allowed in some experiments to watch an audible video while their auditory P1, NI, P2, and mismatch negativity (MMN) event-related potentials (ERPs) to experimental sounds have been measured. However, video sounds may degrade auditory ERPs to experimental sounds. This concern was tested with 19 adults who were instructed to ignore standard and deviant tones presented through headphones while they watched a video with the soundtrack audible in one condition and silent in the other. Video sound impaired the size, latency, and split-half reliability of the MMN, and it decreased the size of the P2. However, it had little effect on the P1 or N1 or on the split-half reliability of the P1—N1—P2 waveform, which was significantly more reliable than the MMN waveform regardless of whether the video sound was on or off. The impressive reliability of the P1 and N1 components allows for the use of video sound during EEG recording, and they may prove useful for assessing auditory processing in listeners who cannot tolerate long testing sessions.

Effect of deviance direction and calculation method on duration and frequency mismatch negativity (MMN)

The mismatch negativity (MMN) component of the auditory event-related potential (ERP) reflects the process of change detection in the auditory system. The present study investigated the effect of deviance direction (increment vs. decrement) and calculation method (traditional vs. same-stimulus) on the amplitude of MMN. MMN was recorded for increments and decrements in frequency and duration in 20 adults. The stimuli (standard/deviant) were 250 Hz/350 Hz (frequency MMN) and 200 ms/300 ms (duration MMN) for increment MMN and vice versa for decrement MMN. Amplitude of MMN was calculated in two ways: the traditional method (subtracting ERP to the standard from the deviant presented in the same block) and the same-stimulus method (subtracting ERP to identical stimuli presented as standard in one block and deviant in another block). We found that increments in frequency produced higher MMN amplitudes compared to decrements for both methods of calculation. For duration deviance, the decrement MMN was absent in the traditional method, while the decrement and increment MMN did not differ for the same-stimulus method. These findings suggest that the brain processes frequency increments and decrements in different ways. The results also suggest the use of same-stimulus method for the calculation of duration MMN when long duration stimuli are used.