Atypical sensory sensitivity as a shared feature between synaesthesia and autism

Abstract

Several studies have suggested that there is a link between synaesthesia and autism but the nature of that link remains poorly characterised. The present study considers whether atypical sensory sensitivity may be a common link between the conditions. Sensory hypersensitivity (aversion to certain sounds, touch, etc., or increased ability to make sensory discriminations) and/or hyposensitivity (desire to stimulate the senses , or a reduced response to sensory stimuli are a recently introduced diagnostic feature of autism spectrum conditions (ASC). Synaesthesia is defined by unusual sensory experiences and has also been linked to a typical cortical hyper-excitability. The Glasgow Sensory Questionnaire (GSQ) was administered to synaesthetes and people with ASC. Both groups reported increased sensory sensitivity relative to controls with a large effect size. Both groups also reported a similar pattern of both increased hyper- and hypo-sensitivities across multiple senses. The AQ (Autism-Spectrum Quotient) scores were elevated in the synaesthetes, and one subscale of this measure (attention to detail) placed synaesthetes within the autistic range. A standard laboratory test of visual stress (the Pattern Glare Test), administered online, corroborated the findings of increased sensitivity to aversive visual stimuli in synaesthetes. We conclude that atypical sensory sensitivity is an important shared feature between autism and synaesthesia.

Tactile hypersensitivity and GABA concentration in the sensorimotor cortex of adults with autism

“…Consistently with previous studies using the GSQ [Takayama et al, ; Ward et al, ], adults with ASD reported more frequent tactile hypersensitivity experiences than NT adults. Given this higher self‐reported tactile hypersensitivity, we could have expected behavioral measurements of tactile sensitivity to show lower detection thresholds or lower frequency discrimination thresholds in the ASD group.…”

“…GABA concentration in the sensorimotor cortex has been correlated to tactile detection thresholds in children with ASD [Puts et al, ]. Note that measurements of tactile detection thresholds do not consistently show hypersensitivity in ASD [Mikkelsen et al, ], despite self‐reported tactile hypersensitivity in ASD [Takayama et al, ; Tavassoli, Miller, Schoen, Nielsen, & Baron‐Cohen, ; Tavassoli et al, ; Ward et al, ]. It is therefore worth investigating the correlations between self‐reported measures of tactile hypersensitivity and GABA concentration.…”

Individual differences in sensory sensitivity: A synthesizing framework and evidence from normal variation and developmental conditions

“…The same pattern, albeit with considerably higher scores, has been found when these measures have been given to special groups including autism and synaesthesia (e.g. Ward et al, 2017). The co-occurrence of hyper-and hypo-sensitivities is a puzzle.…”

“…'op art') can appear to shimmer or induce feelings of nausea. These kinds of atypical sensory sensitivities have been linked to a wide variety of conditions including migraine (Schwedt, 2013), autism spectrum disorder (Tavassoli, Hoekstra, & Baron-Cohen, 2014), ADHD (Bijlenga, Tjon-Ka-Jie, Schuijers, & Kooij, 2017), Tourette syndrome (Belluscio, Jin, Watters, Lee, & Hallett, 2011), and synaesthesia (Ward et al, 2017). One lady with autism describes her experiences thus: "the sensory overload caused by bright lights, fluorescent lights, colours, and patterns makes the body react as if being attacked or bombarded, resulting in such physical symptoms as headaches, anxiety, panic attacks or aggression" (p. 43 Williams, 1994).…”

Is Synaesthesia More Prevalent in Autism Spectrum Conditions? Only Where There Is Prodigious Talent

“…In synaesthesia too, Banissy et al (2009) found a relationship between the modality of synaesthetic experiences (e.g., sensations of colour) and sensory hypersensitivity in those same modalities (e.g., enhanced colour perception). Both synaesthetes and individuals with ASC self-report increased sensory sensitivity across several sensory domains compared to controls (Ward et al, 2017). Thus, atypical sensory experiences occur in both synaesthesia and autism, although whether this supports a direct causal explanation for any co-occurrence of these two conditions remains to be clarified.…”