Impaired duration mismatch negativity in developmental dyslexia

Diagnostic subgroups of developmental dyslexia have different deficits in neural processing of tones and phonemes

Language impairments can have a devastating effect on the individual’s life. Brain damage such as stroke may cause varying degrees of impaired language. Even milder language problems, such as developmental dyslexia or specific language impairment, can have long-lasting detrimental effects on the individual’s life, affecting both success at school as well as motivation and even self-esteem. In recent years, the mismatch negativity (MMN) has been intensively applied to study the neural basis of language impairments. These studies have shown that the MMN, which reflects the early stages of cortical sound discrimination, is abnormal in a large variety of language impairments. Furthermore, a close relationship between the MMN and some language disorders is suggested by significant correlations between the MMN and language test results. Further support is provided by follow-up studies suggesting that the MMN parameters may predict future language problems in children and by investigations indicating that intervention programs with an ameliorating effect also concurrently change the MMN. However, when interpreting the implications of MMN results it is important to acknowledge that this response specifically reflects early stages of auditory discrimination and should, therefore, be combined with measures probing the further steps of auditory processing for a more complete picture of the underlying deficits of language. The current review addresses how the MMN can be used in determining auditory impairments in language disorders such as aphasia, dyslexia, autism spectrum, and specific language impairment.

Altered Processing of Auditory Distractions Under Competing Inputs in Children With Attention-Deficit/Hyperactivity Disorder.

Mismatch negativity (MMN) and P300 event-related potential (ERP) reductions in schizophrenia (SZ) reflect preattentive and attention-mediated auditory processing deficits, respectively. Although both have been linked to cognitive deficits in SZ, their relative contributions to real-world functioning are unclear. We sought to determine the functional significance of disrupted auditory processing in SZ by examining MMN and P300 in typically disabled low-functioning patients and in patients with high levels of independent role functioning. MMN to auditory deviants and P300 to infrequent auditory target and nontarget novel stimuli were assessed in 20 high-functioning SZ patients (HF-SZ), 17 low-functioning patients (LF-SZ), and 35 healthy comparison (HC) subjects. There was a group effect on MMN and P300 amplitudes across stimulus types. MMN was significantly diminished in LF-SZ compared to HF-SZ and HC, and HF-SZ demonstrated comparable MMN to HC. In contrast, P300 was significantly reduced in both LF-SZ and HF-SZ compared to HC. Logistic regression suggested independent sensitivity of MMN to functioning in SZ over and above P300 measures. Neither MMN nor P300 were associated with positive or negative symptom severity. Results replicate MMN and P300 abnormalities in SZ, and also suggest that the neural mechanisms associated with the preattentive detection of auditory deviance are most compromised in patients with functional disability. MMN may index pathophysiological processes that are critical for optimal functioning in SZ.

It has been suggested that auditory and visual sequential processing deficits contribute to phonological disorders in developmental dyslexia. As an alternative explanation to a phonological deficit as the proximal cause for reading disorders, the visual attention span hypothesis (VA Span) suggests that difficulties in processing visual elements simultaneously lead to dyslexia, regardless of the presence of a phonological disorder. In this study, we assessed whether deficits in processing simultaneously displayed visual or auditory elements is linked to dyslexia associated with a VA Span impairment. Sixteen children with developmental dyslexia and 16 age-matched skilled readers were assessed on visual and auditory search tasks. Participants were asked to detect a target presented simultaneously with 3, 9, or 15 distracters. In the visual modality, target detection was slower in the dyslexic children than in the control group on a “serial” search condition only: the intercepts (but not the slopes) of the search functions were higher in the dyslexic group than in the control group. In the auditory modality, although no group difference was observed, search performance was influenced by the number of distracters in the control group only. Within the dyslexic group, not only poor visual search (high reaction times and intercepts) but also low auditory search performance (d′) strongly correlated with poor irregular word reading accuracy. Moreover, both visual and auditory search performance was associated with the VA Span abilities of dyslexic participants but not with their phonological skills. The present data suggests that some visual mechanisms engaged in “serial” search contribute to reading and orthographic knowledge via VA Span skills regardless of phonological skills. The present results further open the question of the role of auditory simultaneous processing in reading as well as its link with VA Span skills.

Mismatch Negativity (MMN) is an evoked potential in response to an acoustical environmental change. Hypothesizing that, for animals to survive, MMN plays important roles in sensing environmental atmosphere, we investigated MMN in the auditory cortex of anesthetized rats in response to changes of frequency and harmony of test tone pulses. We first confirmed in behavioral experiments that rats could categorize consonant and dissonant chords, and thus distinguish this kind of sound feature quality, or ‘qualia.’ In physiological experiments, a surface microelectrode array mapped auditory evoked middle-latency response (P1) and MMN. We found that MMN could be elicited from the difference of qualia between consonant and dissonant chords and that the distributions of chord-elicited MMN were different from those of tone-elicited MMN. In response to pure tones, while middle-latency response (P1) was focally evoked from primary and anterior auditory cortex (A1, AAF), MMN spread toward ventral auditory cortex (VAF) in addition to A1 and AAF. In response to chords, MMN also widely spread over the auditory cortex, yet the largest activation spot was obtained in AAF. We also found an asymmetric property of MMN: Changes from low- to high-frequency tones and from dissonant to consonant chords produced larger MMN. Taken together, MMN in the auditory cortex can be elicited by changes of distinguishable qualia in an asymmetric form, suggesting that MMN reflects a detection of change of particular environmental atmosphere of sounds, which are potentially important for a survival.

ObjectiveThe mismatch negativity (MMN) event-related potential is an index of the pre-attentive stage of neural auditory information processing and an electrophysiological signal indicative of the integrity of auditory information processing with regard to the attention deficit symptom of attention deficit hyperactivity disorder (ADHD). We investigated the association between the MMN amplitude and latency in frontal brain regions and symptom severity in children with ADHD and subclinical ADHD symptoms.MethodsThis study included 29 children: 16 (10 boys; mean age, 13.06 ± 3.67 years) with ADHD (ADHD group) and 13 (eight boys; mean age, 13.40 ± 3.31 years) with sub-clinical ADHD symptoms (subclinical ADHD group). We performed the following assessments: Korean ADHD rating scale-IV (K-ARS-IV), children depression inventory, state/trait anxiety inventory for children, and MMN (measured at Fz, FCz, Cz, and CPz).ResultsThere were no sex or mean age differences between the groups (c2 = −0.01, p = 0.958; Z = −1.88, p = 0.060, respectively). The ADHD group had a significantly higher mean K-ARS-IV score (26.13 ± 9.56 vs. 17.15 ± 11.73, Z = −2.11, p = 0.035). Significant differences were found according to symptom severity in the MMN amplitude at FCz (Z = −2.11, p = 0.035) and MMN latency at Fz and FCz (Z = −2.48, p = 0.013; Z = −2.57, p = 0.010). The K-ARS-IV, K-ARS inattention subscale, and K-ARS hyperactivity-impulsivity subscale scores in the ADHD group correlated significantly with the MMN amplitude at Cz and CPz.ConclusionThis study found differences in the MMN amplitude and latency according to the severity of ADHD symptoms and identified MMN as a potential adjunct to the diagnosis of ADHD.

A popular hypothesis holds that specific reading disability (SRD) and specific language impairment (SLI) result from an impaired ability to process rapid and brief sounds. However, the results of experiments that have tested this hypothesis are incongruous. A number of factors could explain these contradictory findings, including the questionable reliability and validity of rapid auditory processing tasks, individual differences in the auditory processing abilities of SRD and SLI populations, the age of listeners, the quality of control groups, and the relationship between verbal and non-verbal auditory processing abilities. These issues highlight the need for future studies to (1) establish the reliability and validity of psychophysical tasks used to assess rapid auditory processing; (2) report the rapid auditory processing scores of individuals rather than just group means; (3) include a wide range of reading and spoken language tests to determine the literacy and oral language profile of people who demonstrate an auditory processing deficit; (4) include clinical comparison groups to determine whether a rapid auditory processing deficit is related specifically to written and spoken language impairments; and (5) examine the relationship between low-level non-verbal, verbal, and phonological processing abilities.

Auditory processing disorders (APDs) are associated with an inability to process auditory information which cannot be explained by abnormal hearing thresholds. This review focuses on APDs that are liable to be found in subjects with language-based learning disabilities such as dyslexia. Although the causal relationship between the presence of an APD and reading deficits is still poorly understood, it is clear that in many cases (estimated range between 30-50%) the presence of an APD may serve as a marker of language-based learning problems. While some dyslexic children can be characterized by poor performances in auditory temporal processing (resolution, masking, ordering, integration) they can also experience hearing difficulties with competing or degraded acoustic signals (for example, during dichotic listening or in the presence of a noisy background). Behavioural hearing deficits are not always found in dyslexic children; when present they may be explained, at least partly, by the task complexity which induces strong cognitive load. However, there is no doubt that the co-morbidity of APD and dyslexia can create difficulties in communication and academic skills. In addition to these behavioural indices of APD, evidence for abnormal function of the descending auditory pathway is provided in dyslexia. We here present preliminary results showing 1) differences in the developmental trajectories when normal reading and dyslexic children are compared for auditory descending pathway function and 2) deficient high level process (attention) which appears in literacy problems and auditory processing deficits (dichotic listening) through feedback connections from higher to lower areas. These abnormalities, in turn, may be accompanied by different behavioural manifestations of APD. Keywords: Auditory processing disorder, dyslexia, psychoacoustic measurements, dichotic listening, auditory attention, auditory memory, auditory asymmetry, medial olivo-cochlear system, psychoacoustic measurements auditory memory

Modulation of auditory temporal processing, speech in noise perception, auditory-verbal memory, and reading efficiency by anodal tDCS in children with dyslexia

Dyslexia affects 5–10% of school-aged children and is therefore one of the most common learning disorders. Research on auditory event related potentials (AERP), particularly the mismatch negativity (MMN) component, has revealed anomalies in individuals with dyslexia to speech stimuli. Furthermore, candidate genes for this disorder were found through molecular genetic studies. A current challenge for dyslexia research is to understand the interaction between molecular genetics and brain function, and to promote the identification of relevant endophenotypes for dyslexia. The present study examines MMN, a neurophysiological correlate of speech perception, and its potential as an endophenotype for dyslexia in three groups of children. The first group of children was clinically diagnosed with dyslexia, whereas the second group of children was comprised of their siblings who had average reading and spelling skills and were therefore “unaffected” despite having a genetic risk for dyslexia. The third group consisted of control children who were not related to the other groups and were also unaffected. In total, 225 children were included in the study. All children showed clear MMN activity to/da/−/ba/contrasts that could be separated into three distinct MMN components. Whilst the first two MMN components did not differentiate the groups, the late MMN component (300–700 ms) revealed significant group differences. The mean area of the late MMN was attenuated in both the dyslexic children and their unaffected siblings in comparison to the control children. This finding is indicative of analogous alterations of neurophysiological processes in children with dyslexia and those with a genetic risk for dyslexia, without a manifestation of the disorder. The present results therefore further suggest that the late MMN might be a potential endophenotype for dyslexia.

The simultaneous auditory processing skills of 17 dyslexic children and 17 skilled readers were measured using a dichotic listening task. Results showed that the dyslexic children exhibited difficulties reporting syllabic material when presented simultaneously. As a measure of simultaneous visual processing, visual attention span skills were assessed in the dyslexic children. We presented the dyslexic children with a phonological short-term memory task and a phonemic awareness task to quantify their phonological skills. Visual attention spans correlated positively with individual scores obtained on the dichotic listening task while phonological skills did not correlate with either dichotic scores or visual attention span measures. Moreover, all the dyslexic children with a dichotic listening deficit showed a simultaneous visual processing deficit, and a substantial number of dyslexic children exhibited phonological processing deficits whether or not they exhibited low dichotic listening scores. These findings suggest that processing simultaneous auditory stimuli may be impaired in dyslexic children regardless of phonological processing difficulties and be linked to similar problems in the visual modality.

Mismatch Negativity in children with Phonological Disorders

Multiple sclerosis (MS) is one of the most common neurological diseases in North America and it is frequently associated with sensory processing difficulties, cognitive deficits, and psychiatric illness. While many studies have examined cognitive deficits in MS measured by behavioural responses and neuroimaging techniques, only a few studies have examined neurophysiological measures of auditory functioning in MS, such as the mismatch negativity (MMN). The MMN is an event-related potential that indicates automatic auditory change detection. This study examined whether MMN endpoints measured by electroencephalography (EEG) differ in individuals with relapsing-remitting MS compared to healthy controls and whether the symptomatology of MS, including symptoms of depression and fatigue, are related to MMN measures. A multi-feature MMN paradigm, which includes five distinct deviant tones, was used to assess auditory cortex function in MS. There were no significant differences in MMN amplitudes or latencies between the MS and control group (p < 0.05) and corresponding effect sizes were small. However, there was a correlation between reduced MMN amplitudes in response to an intensity deviant and physician-reported disability. The intensity MMN may be more sensitive to deterioration in this population. Ultimately, this study provides a comprehensive profile of early auditory processing abilities in MS and suggests that a reduction in the MMN response may be representative of disease severity in MS.

Developmental dyslexia, characterized by difficulty in reading, has been associated with phonological and orthographic processing deficits. fMRI was performed on dyslexic and normal-reading children (8-12 years old) during phonological and orthographic tasks of rhyming and matching visually presented letter pairs. During letter rhyming, both normal and dyslexic reading children had activity in left frontal brain regions, whereas only normal-reading children had activity in left temporo-parietal cortex. During letter matching, normal-reading children showed activity throughout extrastriate cortex, especially in occipito-parietal regions, whereas dyslexic children had little activity in extrastriate cortex during this task. These results indicate dyslexia may be characterized in childhood by disruptions in the neural bases of both phonological and orthographic processes important for reading.