Jyutika A. Mehta

The pattern of sensory processing abnormalities in autism

The study was undertaken to evaluate the nature of sensory dysfunction in persons with autism. The cross-sectional study examined auditory, visual, oral, and touch sensory processing, as measured by the Sensory Profile, in 104 persons with a diagnosis of autism, 3–56 years of age, gender-and age-matched to community controls. Persons with autism had abnormal auditory, visual, touch, and oral sensory processing that was significantly different from controls. This finding was also apparent when the high and low thresholds of these modalities were examined separately. At later ages for the group with autism, lower levels of abnormal sensory processing were found, except for low threshold touch, which did not improve significantly. There was a significant interaction in low threshold auditory and low threshold visual, suggesting that the two groups change differently over time on these variables. These results suggest that sensory abnormalities in autism are global in nature (involving several modalities) but have the potential to improve with age.

Sensory correlations in autism

This study examined the relationship between auditory, visual, touch, and oral sensory dysfunction in autism and their relationship to multisensory dysfunction and severity of autism. The Sensory Profile was completed on 104 persons with a diagnosis of autism, 3 to 56 years of age. Analysis showed a significant correlation between the different processing modalities using total scores. Analysis also showed a significant correlation between processing modalities for both high and low thresholds, with the exception that auditory high threshold processing did not correlate with oral low threshold or touch low threshold processing. Examination of the different age groups suggests that sensory disturbance correlates with severity of autism in children, but not in adolescents and adults. Evidence from this study suggests that: all the main modalities and multisensory processing appear to be affected; sensory processing dysfunction in autism is global in nature; and sensory processing problems need to be considered part of the disorder.

Effectiveness of N,N-Dimethylglycine in Autism and Pervasive Developmental Disorder

N,N-dimethylglycine, a dietary supplement, has been reported to be beneficial in children with autism and pervasive developmental disorder. We examined the effectiveness of dimethylglycine in children with autism and pervasive developmental disorder in a double-blind, placebo-controlled study. Thirty-seven children between 3 and 11 years of age with a diagnosis of autism and/or pervasive developmental disorder were gender and age matched and randomly assigned to receive either placebo or dimethylglycine for 4 weeks. All children were assessed before and after treatment on two behavioral measures, the Vineland Maladaptive Behavior Domain and the Aberrant Behavior Checklist. Standardized neurologic examinations before and after treatment on 33 children showed no change. An overall improvement on all behavioral measures was observed for both the placebo and the dimethylglycine groups. However, the improvement among the children who received dimethylglycine was not statistically different from the improvement observed among the children who received the placebo. The children who participated in this study were a heterogeneous group, and their apparent responses to the dimethylglycine varied. Some children appeared to respond positively to the dimethylglycine, and there was a smaller proportion of negative changes in the dimethylglycine group, but the quantitative changes in the dimethylglycine behavioral assessments were not significantly different from what was observed among children who received placebo. (J Child Neurol 2001;16:169-173).

Shared Brain Connectivity Issues, Symptoms, and Comorbidities in Autism Spectrum Disorder, Attention Deficit/Hyperactivity Disorder, and Tourette Syndrome

The prevalence of neurodevelopmental disorders, including autism spectrum disorder (ASD), attention deficit/hyperactivity disorder (ADHD), and Tourette syndrome (TS), has increased over the past two decades. Currently, about one in six children in the United States is diagnosed as having a neurodevelopmental disorder. Evidence suggests that ASD, ADHD, and TS have similar neuropathology, which includes long-range underconnectivity and short-range overconnectivity. They also share similar symptomatology with considerable overlap in their core and associated symptoms and a frequent overlap in their comorbid conditions. Consequently, it is apparent that ASD, ADHD, and TS diagnoses belong to a broader spectrum of neurodevelopmental illness. Biologically, long-range underconnectivity and short-range overconnectivity are plausibly related to neuronal insult (e.g., neurotoxicity, neuroinflammation, excitotoxicity, sustained microglial activation, proinflammatory cytokines, toxic exposure, and oxidative stress). Therefore, these disorders may a share a similar etiology. The main purpose of this review is to critically examine the evidence that ASD, ADHD, and TS belong to a broader spectrum of neurodevelopmental illness, an abnormal connectivity spectrum disorder, which results from neural long-range underconnectivity and short-range overconnectivity. The review also discusses the possible reasons for these neuropathological connectivity findings. In addition, this review examines the role and issue of axonal injury and regeneration in order to better understand the neuropathophysiological interplay between short- and long-range axons in connectivity issues.

Electrophysiological correlates of word comprehension: Event-related potential (ERP) and independent component analysis (ICA)

In this study we asked to what extent auditory evoked potentials can help us to understand the complex processes underlying word comprehension. Monosyllabic and bisyllabic words were presented to 34 young adults in the context of a semantic category judgment. The basic paradigm assessed the typicality effect, the tendency for classification of members of a category to be made more accurately and more rapidly for strong exemplars than for weak exemplars. Event-related potentials (ERPs) were recorded from 30 active scalp electrodes. The ERP waveform in response to the semantic categorization of a word was characterized by unique activity in four temporal intervals; (1) a negative peak at a latency of about 100 ms, (2) a positive peak at a latency of about 200 ms, (3) a broad negativity extending over the latency range from 200 to 600 ms, and (4) a broad positivity extending from 600 to 1400 ms. Independent component analysis (ICA) of the individual EEG epochs yielded four maximally independent components, interpreted as (1) exogenous detection of a change in the acoustic environment, followed by allocation of cognitive resources, especially sustained attention, to the analysis of subsequent acoustic events, (2) phonological processing, (3) semantic processing, and (4) decision processing. The morphologies of the four ICA waveforms were consistent with a parallel processing, interactive model of word recognition, and subsequent semantic categorization.

Effects of childhood hearing loss on organization of semantic memory: Typicality and relatedness

Objective: The purpose of this research was to study how early childhood hearing loss affects development of concepts and categories, aspects of semantic knowledge that allow us to group and make inferences about objects with common properties, such as dogs versus cats. We assessed category typicality and out-of-category relatedness effects. The typicality effect refers to performance advantage (faster reaction times, fewer errors) for objects with a higher number of a categorys characteristic properties; the out-of-category relatedness effect refers to performance disadvantage (slower reaction times and more errors) for out-of-category objects that share some properties with category members. Design: We applied a new childrens speeded category-verification task (vote “yes” if the pictured object is clothing). Stimuli were pictures of typical and atypical category objects (e.g., pants, glove) and related and unrelated out-of-category objects (e.g., necklace, soup). Participants were 30 children with hearing impairment (HI) who were considered successful hearing aid users and who attended regular classes (mainstreamed) with some support services. Ages ranged from 5 to 15 yr (mean = 10 yr 8 mo). Results were related to normative data from Jerger and Damian (2005). Results: Typical objects consistently showed preferential processing (faster reaction times, fewer errors), and related out-of-category objects consistently showed the converse. Overall, results between HI and normative groups exhibited striking similarity. Variation in speed of classification was influenced primarily by age and age-related competencies, such as vocabulary skill. Audiological status, however, independently influenced performance to a lesser extent, with positive responses becoming faster as degree of hearing loss decreased and negative responses becoming faster as age of identification/amplification/education decreased. There were few errors overall. Conclusions: The presence of a typicality effect indicates that 1) the structure of conceptual representations for at least one category in the HI group was based on characteristic properties with an uneven distribution among members, and 2) typical objects with a higher number of characteristic properties were more easily accessed and/or retrieved. The presence of a relatedness effect indicates that the structure of representational knowledge in the HI group allowed them to appreciate semantic properties and understand that properties may be shared between categories. Speculations linked the association 1) between positive responses and degree of hearing loss to an increase in the quality, accessibility, and retrievability of conceptual representations with better hearing; and 2) between negative responses and age of identification/amplification/education to an improvement in effortful, postretrieval decision-making proficiencies with more schooling and amplified auditory experience. This research establishes the value of our new approach to assessing the organization of semantic memory in children with HI.