[Synesthesia and autism spectrum disorder : journey on a sensory möbius strip]

In autism spectrum disorder, aphantasia-the absence of mental imagery-and synesthesia-the automatic interaction of sensory systems in response to an external stimulus-mark the extremes of a perceptual spectrum, like a Möbius strip. Synesthesia can link letters and colors, sounds and shapes, words and tastes, spatial mapping and proprioception. More common in this population, it has prompted research into its genetic, neurobiological, cognitive, perceptual and cerebral bases, revealing hyperconnectivity and convergences with sensory overloads of autism spectrum disorder (ASD). Stimuli can activate auditory, visual, olfactory, proprioceptive, nociceptive, or vestibular responses. A phenomenon at the heart of reality, it embodies the unique diversity of ways which people diagnosed with ASD translate and represent the sensory world.