Testing the Efficacy of 100mg Vitamin-B6 Daily for Sensory Reactivity in Autism

Sensory hyperreactivity will be measured by a subscale of the Sensory Processing Inventory (SP3D.

Sensory hyperreactivity will be measured by a subscale of the Comprehensive Autistic Trait Inventory (CATI).

Anxiety will be measured using the Screen for Adult Anxiety Related Disorders (SCAARED) questionnaire.

The concentration of different forms of Vitamin B6 in blood plasma will be measured (Pyridoxal-5'-phosphate, pyridoxine, pyridoxal, pyridoxamine)

Adult Attention Deficit Hyperreactivity Disorder Self-Report Scale (ASRS-v1.1)

These will be measured using the other subscales of the Sensory Processing Inventory (SP3D) that do not constitute the primary sensory hyperreactivity outcome described above.

Pittsburgh Sleep Quality Index (PSQI)

Psychophysical measurements of the contrast threshold will be made, which correspond to the minimum physical stimulus contrast that can be reliably detected by an observer. The test measures the increase in the threshold caused by introducing spatial inhibition of the target stimuli, which is a parameter that has been shown to correlate with GABA concentration in the brain (Yoon et al., 2010).

Psychophysical measurements of the motion duration threshold will be made, which correspond to the number of milliseconds an observer requires to detect whether a Gabor patch is drifting left or right. The test measures the increase in the threshold caused by spatial inhibition, which is a parameter that has been shown to differ in various patient groups, including autism (Foss-Feig et al. 2013).

A test based on presenting ambiguous visual stimuli that cause perceptual reversals; how frequently the perceptual reversals occur is measured and has been shown to be related to GABA levels (Mentch et al., 2019).

A test based on presenting ambiguous visual stimuli that cause perceptual reversals; the proportion of time for which the stimulus appears unclear rather than stable is measured and has been shown to be related to GABA levels (Mentch et al., 2019).

The Weber fraction is the percentage change in a physical quantity required for an observer to reliably detect that a change has occurred, and for a specific stimulus type it is generally a fixed percentage regardless of the magnitude of the stimuli. We will measure the Weber Fraction for visual size perception at four separate starting sizes, and the outcome measure derived from doing that will be a measurement of the stability/instability of the Weber Fraction across the four starting sizes. It has been reported that in autism the general finding of fixed Weber fractions across a range of physical stimuli does not hold (Hadad & Schwartz, 2019): we are taking the opportunity to replicate this finding.

Magnitude of the tilt illusion is a correlate of GABA concentration in the occipital cortex (Song et al., 2017).

Magnitude of the Ebbinghaus illusion is a correlate of gamma y-Aminobutyric acid (GABA) concentration in the parietal lobe (Song et al. 2017)