Neurophysiological hyperresponsivity to sensory input in autism spectrum disorders

Area of Science:

• Neuroscience
• Developmental Neuroscience
• Clinical Neuroscience

Background:

• Atypical sensory processing is common in autism spectrum disorder (ASD).
• Sensory hypersensitivity in ASD may stem from neural hyperexcitability.
• Investigating visual evoked responses can model sensory system neural responsivity in ASD.

Purpose of the Study:

• To model neural responsivity of sensory systems in ASD.
• To examine visual evoked responses to parametric increases in stimulus contrast in individuals with ASD.
• To investigate the relationship between neural responsivity and sensory difficulties in ASD.

Main Methods:

• Steady-state visual evoked potential (SSVEP) study comparing 13 high-functioning individuals with ASD and 12 typically developing (TD) individuals.
• Stimuli included vertical circular gratings at varying contrasts (5-90%) oscillating at 3.76 Hz.
• Calculated average spectral power at the stimulus oscillation frequency for each contrast level.

Main Results:

• The ASD group exhibited a significantly greater rate of increase in evoked sensory response magnitude with higher contrasts.
• Individuals with ASD showed disproportionately elevated activation at higher stimulus contrasts.
• Approximately 45% of ASD participants displayed response increase rates exceeding all TD participants, correlating with parental reports of sensory difficulties.

Conclusions:

• Increased visual responses to contrast manipulation suggest heightened sensory cortex excitability in ASD.
• Heightened neural excitability was identified in a significant subset of ASD participants, not all.
• This pattern indicates that individuals with heightened excitability may represent a distinct neurobiological subgroup within ASD requiring individualized interventions.