Papers by Mervyn Hardiman
Journal of Neurodevelopmental Disorders, 2014
Developmental disorders of oral and written language have been linked to deficits in the processi... more Developmental disorders of oral and written language have been linked to deficits in the processing of auditory information. However, findings have been inconsistent, both for behavioural and electrophysiological measures. In this study, we examined event-related potentials (ERPs) in 20 6- to 14-year-old children with developmental dyslexia and 20 age-matched controls, divided into younger (6-11 years, n = 10) and older (11-14 years, n = 10) age bands. We focused on early (mismatch negativity; MMN) and late (late discriminative negativity; LDN) conventional mismatch responses and associated measures derived from time-frequency analysis (inter-trial coherence and event-related spectral perturbation). Responses were elicited using an auditory oddball task, whereby a stream of 1000-Hz standards was interspersed with rare large (1,200 Hz) and small (1,030 Hz) frequency deviants. Conventional analyses revealed no significant differences between groups in the size of the MMN to either large or small frequency deviants. However, the younger age band of children with dyslexia showed an enhanced inter-trial coherence in the theta frequency band over the time window corresponding to the MMN to small deviants. By contrast, these same children showed a reduced-amplitude LDN for the small deviants relative to their age-matched controls, whilst the older children with dyslexia showed a shorter and less intense period of event-related desynchronization over this time window. Initial detection and discrimination of auditory frequency change appears normal or even enhanced in children with dyslexia. Rather, deficits in late-stage auditory processing appear to be a feature of this population.
• Oddball design: 1 standard 2 deviants • Pseudorandom presentation of stimuli not < 2 DEV before... more • Oddball design: 1 standard 2 deviants • Pseudorandom presentation of stimuli not < 2 DEV before STD • Random presentation of 2 blocks of Tones • Present the same stimuli to both FH+ and FH-groups • Stimulus presented to right side only • Told not to attend to sounds • Watched a silent video
Background: The ability to repeat polysyllabic nonwords such as ''blonterstaping'' has frequently... more Background: The ability to repeat polysyllabic nonwords such as ''blonterstaping'' has frequently been shown to correlate with language learning ability but it is not clear why such a correlation should exist. Three alternative explanations have been offered, stated in terms of differences in: (a) perceptual ability; (b) efficiency of phonological loop functioning; (c) preexisting vocabulary knowledge and/or articulatory skills. In the present study, we used event-related potentials to assess the contributions from these three factors to explaining individual variation in nonword repetition ability.
Background: Are developmental language disorders caused by poor auditory discrimination? This is ... more Background: Are developmental language disorders caused by poor auditory discrimination? This is a popular theory, but behavioural evidence has been inconclusive. Here we studied children with specific language impairment, measuring the brain's electrophysiological response to sounds in a passive paradigm. We focused on the T-complex, an event-related peak that has different origins and developmental course from the well-known vertex response.
Journal of Neuroscience, 2010
Poor discrimination of nonlinguistic sounds has been implicated in language-learning problems in ... more Poor discrimination of nonlinguistic sounds has been implicated in language-learning problems in children, but research evidence has been inconsistent. This study included 32 participants with specific language impairment (SLI) and 32 typically developing controls aged 7-16 years. Frequency discrimination thresholds were estimated in a task where participants had to distinguish a higher-frequency tone from a 1000 Hz tone. Neurophysiological responses were assessed in an oddball paradigm. Stimuli were either 1030 or 1200 Hz pure tones (deviants) presented in a series of standard 1000 Hz tones, or syllables (deviant [da] or [bi] in a series of standard /ba/). On the behavioral task, children (7-to 11-year-olds) had high thresholds, regardless of language status, but teenagers (12-16 years) with SLI had higher thresholds than their controls.
Psychophysiology, 2010
Mismatch negativity (MMN) is measured by subtracting the averaged response to a set of standard s... more Mismatch negativity (MMN) is measured by subtracting the averaged response to a set of standard stimuli from the averaged response to rarer deviant stimuli, and taking the amplitude of this difference wave in a given time window. This method is problematic when used to evaluate individuals, because there is no estimate of variance. We describe a new approach, in which independent components with high trial-by-trial variance are first removed. Next, each deviant response has the preceding standard response subtracted, giving a set of single trial difference waves. We illustrate this approach in analysis of MMN to brief tones in 17 adults. The best criterion for MMN combined t-test with an index of inter-trial coherence, giving significant MMN in 14 (82%) of individuals. Single-trial methods can indicate which people show MMN. However, in some clinically normal individuals there was no MMN, despite good behavioral discrimination of stimuli.
PLoS ONE, 2012
Background: Nonword repetition, the ability to retain and repeat unfamiliar sequences of phonemes... more Background: Nonword repetition, the ability to retain and repeat unfamiliar sequences of phonemes is usually impaired in children with specific language impairment (SLI), but it is unclear whether this explains slow language learning. Traditional nonword repetition tests involve a single presentation of nonwords for immediate repetition. Here we considered whether rate of learning of novel phonological sequences was impaired when the same items were presented repeatedly.
NeuroReport, 1999
Subcortical visual inputs to motion-selective cortex in primates survive after damage to the prim... more Subcortical visual inputs to motion-selective cortex in primates survive after damage to the primary visual cortex (area 17/V1). Activation of human motion cortex was examined using scalp electrodes in a V1-damaged hemianope. Blind field motion-onset visual evoked potentials (VEPs) shared many of the characteristics associated with sighted vision but were smaller in amplitude and had longer latencies. The representative negative wave (C(II) peak) showed typical dependency on stimulus contrast, its peak latency increased and amplitude decreased as contrast decreased, reflecting the difficulty with which directional information could be detected. VEPs were present at contrasts below 25% when blind field motion was imperceptible even though direction guessing was paradoxically accurate. Subcortical inputs to motion cortex contribute to visual experience but not to conscious perception.
The Journal of Comparative Neurology, 1989
Visual projections to the pontine nuclei in the rabbit were examined by means of both orthograde ... more Visual projections to the pontine nuclei in the rabbit were examined by means of both orthograde and retrograde tracing of WGA-HRP. The tecto-pontine projection was examined following microinjections of WGA-HRP in the right superior colliculus. The projection to the pontine nuclei is strictly ipsilateral and terminates at middle and caudal levels of the pons. The projection is absent in rostral pontine nuclei. The strongest projection is to the dorsal border of the dorsolateral pontine nuclei and is the only projection seen when the primary injection site is confined to superficial laminae. When the primary injection site also includes intermediate and deep laminae, patches of labelled terminals are also seen within dorsolateral, lateral, peduncular, paramedian, and ventral pontine nuclei as well as in the contralateral nucleus reticularis tegmenti pontis. The striate corticopontine projection was also examined with orthograde tracing of WGA-HRP. The striate corticopontine projection is ipsilateral. Most labelled terminals were seen in dorsolateral and lateral pontine nuclei throughout the rostral half of pons with some additional terminal labelling in paramedian and peduncular nuclei. Labelled terminals were also seen in ventral pontine nuclei throughout the middle and caudal levels of the pons. In a retrograde tracing study, visual projections to the pontine nuclei were examined following microinjections of WGA-HRP into the pontine nuclei. Labelled cells were seen ipsilaterally in superficial and deep laminae of the superior colliculus and in layer V of striate and surrounding occipital cortex. The pontine nuclei also receive ipsilateral projections from the ventral lateral geniculate, the nucleus of the optic tract, anterior and posterior pretectal nuclei, and the dorsal and medial terminal nuclei of the accessory optic system. These pathways are potential sources of visual input to the cerebellum.
Experimental Brain Research, 1992
We examined the effects of cerebellar cortical lesions upon conditioned nictitating membrane resp... more We examined the effects of cerebellar cortical lesions upon conditioned nictitating membrane responses in rabbits. Using extended postoperative conditioning and unpaired presentations of the conditioned stimuli (CSs), we confirmed that combined lesions of lobules HVI and ansiform lobe abolished conditioned responses (CRs) established to light and white noise CSs. Extended retraining enabled some slight recovery of CR frequencies. Less extensive cortical lesions produced initial abolition of CRs but allowed more complete recoveries. Although CR frequencies and amplitudes were profoundly depressed by cortical lesions, unconditioned response (UR) amplitudes to periorbital electrical stimulation were enhanced. The dissociation of lesion effects upon conditioned and unconditioned responses is consistent with the suggestion that cerebellar cortical mechanisms are important for the learning and execution of eyeblink conditioning.
Experimental Brain Research, 1985
European Journal of Neuroscience, 1992
Developmental Science, 2011
Behavioural and electrophysiological studies give differing impressions of when auditory discrimi... more Behavioural and electrophysiological studies give differing impressions of when auditory discrimination is mature. Ability to discriminate frequency and speech contrasts reaches adult levels only around 12 years of age, yet an electrophysiological index of auditory discrimination, the mismatch negativity (MMN), is reported to be as large in children as in adults. Auditory ERPs were measured in 30 children (7 to 12 years), 23 teenagers (13 to 16 years) and 32 adults (35 to 56 years) in an oddball paradigm with tone or syllable stimuli. For each stimulus type, a standard stimulus (1000 Hz tone or syllable [ba]) occurred on 70% of trials, and one of two deviants (1030 or 1200 Hz tone, or syllables [da] or [bi]) equiprobably on the remaining trials. For the traditional MMN interval of 100-250 ms post-onset, size of mismatch responses increased with age, whereas the opposite trend was seen for an interval from 300 to 550 ms post-onset, corresponding to the late discriminative negativity (LDN). Time-frequency analysis of single trials revealed that the MMN resulted from phase-synchronization of oscillations in the theta (4-7 Hz) range, with greater synchronization in adults than children. Furthermore, the amount of synchronization was significantly correlated with frequency discrimination threshold. These results show that neurophysiological processes underlying auditory discrimination continue to develop through childhood and adolescence. Previous reports of adult-like MMN amplitudes in children may be artefactual results of using peak measurements when comparing groups that differ in variance.
Developmental Science, 2007
It has been proposed that specific language impairment (SLI) is the consequence of low-level abno... more It has been proposed that specific language impairment (SLI) is the consequence of low-level abnormalities in auditory perception. However, studies of long-latency auditory ERPs in children with SLI have generated inconsistent findings. A possible reason for this inconsistency is the heterogeneity of SLI. The intraclass correlation (ICC) has been proposed as a useful statistic for evaluating heterogeneity because it allows one to compare an individual&amp;amp;amp;amp;amp;amp;#39;s auditory ERP with the grand average waveform from a typically developing reference group. We used this method to reanalyse auditory ERPs from a sample previously described by Uwer, Albrecht and von Suchodoletz (2002). In a subset of children with receptive SLI, there was less correspondence (i.e. lower ICC) with the normative waveform (based on the control grand average) than for typically developing children. This poorer correspondence was seen in responses to both tone and speech stimuli for the period 100-228 ms post stimulus onset. The effect was lateralized and seen at right- but not left-sided electrodes.
Developmental Science, 2007
The auditory event-related potential (ERP) is obtained by averaging electrical impulses recorded ... more The auditory event-related potential (ERP) is obtained by averaging electrical impulses recorded from the scalp in response to repeated stimuli. Previous work has shown large differences between children, adolescents and adults in the late auditory ERP, raising the possibility that analysis of waveform shape might be useful as an index of brain maturity. We reanalysed auditory ERPs from samples previously described by and , using the intraclass correlation (ICC) as a global measure of similarity of an individual's waveform to a grand average comparison waveform for each age band. Three developmental periods were clearly distinguished: 5 to 12 years, 13 to 16 years, and adulthood. However, within each of these periods, there was no evidence of any developmental progression with age.
Brain and Language, 2013
Three converging lines of evidence have suggested that cerebellar abnormality is implicated in de... more Three converging lines of evidence have suggested that cerebellar abnormality is implicated in developmental language and literacy problems. First, some brain imaging studies have linked abnormalities in cerebellar grey matter to dyslexia and specific language impairment (SLI). Second, theoretical accounts of both dyslexia and SLI have postulated impairments of procedural learning and automatisation of skills, functions that are known to be mediated by the cerebellum. Third, motor learning has been shown to be abnormal in some studies of both disorders. We assessed the integrity of face related regions of the cerebellum using Pavlovian eyeblink conditioning in 7-11 year-old children with SLI. We found no relationship between oral language skills or literacy skills with either delay or trace conditioning in the children. We conclude that this elementary form of associative learning is intact in children with impaired language or literacy development.
Brain and Language, 2012
We assessed the relationship between brain structure and function in 10 individuals with specific... more We assessed the relationship between brain structure and function in 10 individuals with specific language impairment (SLI), compared to six unaffected siblings, and 16 unrelated control participants with typical language. Voxel-based morphometry indicated that grey matter in the SLI group, relative to controls, was increased in the left inferior frontal cortex and decreased in the right caudate nucleus and superior temporal cortex bilaterally. The unaffected siblings also showed reduced grey matter in the caudate nucleus relative to controls. In an auditory covert naming task, the SLI group showed reduced activation in the left inferior frontal cortex, right putamen, and in the superior temporal cortex bilaterally. Despite spatially coincident structural and functional abnormalities in frontal and temporal areas, the relationships between structure and function in these regions were different. These findings suggest multiple structural and functional abnormalities in SLI that are differently associated with receptive and expressive language processing.
Brain and Language, 2008
In a previous behavioral study, we showed that parents of children with SLI had a subclinical def... more In a previous behavioral study, we showed that parents of children with SLI had a subclinical deficit in phonological short-term memory. Here, we tested the hypothesis that they also have a deficit in nonverbal auditory sensory memory. We measured auditory sensory memory using a paradigm involving an electrophysiological component called the mismatch negativity (MMN). The MMN is a measure of the brain's ability to detect a difference between a frequent standard stimulus (1000 Hz tone) and a rare deviant one (1200 Hz tone). Memory effects were assessed by varying the inter-stimulus interval (ISI) between the standard and deviant. We predicted that parents of children with SLI would have a smaller MMN than parents of typically developing children at a long ISI (3000 ms), but not at a short one (800 ms). This was broadly confirmed. However, individual differences in MMN amplitude did not correlate with measures of phonological short-term memory. Attenuation of MMN amplitude at the longer ISI thus did not provide unambiguous support for the hypothesis of a reduced auditory sensory memory in parents of affected children. We conclude by reviewing possible explanations for the observed group effects.
Behavioural Brain Research, 1984
verters and non-inverters which show that in adduction writing -i.e., from left to right with the... more verters and non-inverters which show that in adduction writing -i.e., from left to right with the left hand -the IHP may well be advantageous on mechanical grounds.
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Papers by Mervyn Hardiman