Neurophysiological hyperresponsivity to sensory input in autism spectrum disorders

Abstract

BackgroundAtypical sensory processing is a common clinical observation in autism spectrum disorder (ASD). Neural hyperexcitability has been suggested as the cause for sensory hypersensitivity, a frequently reported clinical observation in ASD. We examined visual evoked responses to parametric increases in stimulus contrast in order to model neural responsivity of sensory systems in ASD.MethodsThirteen high-functioning individuals with ASD and 12 typically developing (TD) individuals completed a steady-state visual evoked potential study. Stimuli were vertical circular gratings oscillating at 3.76 Hz at varying contrasts (5, 10, 20,…, 90 % contrast, 10 levels). The average spectral power at the stimulus oscillation frequency was calculated for each contrast level.ResultsThe magnitude of evoked sensory responses increased at a significantly greater rate and resulted in disproportionately elevated activation with higher contrasts in the ASD group. Approximately 45 % of ASD participants had rates of response increases greater than any TD participant. This alteration was highly associated with parental reports of these participants’ sensory difficulties.ConclusionsGreater increases in visual responses over contrast manipulation suggest heightened excitability in the sensory cortex in ASD participants. Heightened neural excitability was observed in a substantial portion but not all of the ASD participants. This pattern suggests that individuals with higher excitability may constitute a neurobiologically distinct subgroup requiring individualized treatment interventions.

<p>Assessments of Amino Acids, Ammonia and Oxidative Stress Among Cohort of Egyptian Autistic Children: Correlations with Electroencephalogram and Disease Severity</p>

“…Additionally, Yousef et al 45 reported a significant relationship between the EEG abnormalities and autism severity and concluded that the severity of autistic symptom may be related to an underlying neurological basis in the form of changes and alteration in cortical excitability of varying degrees in patients with ASD and few of these affected patients may have neuronal hyperactivity. 46 In the current study, we found non-significant differences in the EEG findings and autism severity as assessed by CARS in the studied children with ASD in terms of the frequency of EEG abnormalities, type of discharge and background organization. As the normal interictal EEG does not exclude a clinical diagnosis of epilepsy and surfacebased scalp EEG is not completely presentative for the whole entire brain as many deep-seated cortical gyri are unable to be detected without intracranial electrodes placed directly over the underlying cortex.…”

Neural synchronization deficits linked to cortical hyper-excitability and auditory hypersensitivity in fragile X syndrome

“…First, comparative work is necessary to determine the degree to which our findings occur in other neurodevelopmental disabilities, several of which have associated sensory sensitivities as seen in FXS [47]. While evidence exists for impaired phase-locking ability, increased power, and alpha-gamma phase-amplitude coupling abnormalities in other disorders such as ASD [48–50], these studies primarily describe broad-band power abnormalities and phase-locking deficits, whereas the most salient abnormalities in FXS were seen in the gamma band (but see [51] for gamma deficits in very young boys with ASD).…”

Event related potential analysis techniques for autism spectrum disorders: A review

“…Hyper-excitability of neurons is accounted as the reason for this phenotype. The condition of hypersensitivity on presentation of visual stimuli was studied (Takarae et al, 2016). The visual evoked potentials were recorded from high-functioning individuals with ASD and typical controls by presenting vertical circular gratings at different contrasts (5, 10, 20….90% contrast) as stimuli and the spectral power at varying contrasts was computed using DFT.…”