People with autism perceive drastic illusory changes for repeated verbal stimuli

Functional coupling between auditory memory and verbal transformations

The ability to parse sound mixtures into coherent auditory objects is fundamental to cognitive functions, such as speech comprehension and language acquisition. Yet, we still lack a clear understanding of how auditory objects are formed. To address this question, we studied a speech-specific case of perceptual multistability, called verbal transformations (VTs), in which a variety of verbal forms is induced by continuous repetition of a physically unchanging word. Here, we investigated the degree to which auditory memory through sensory adaptation influences VTs. Specifically, we hypothesized that when memory persistence is longer, participants are able to retain the current verbal form longer, resulting in sensory adaptation, which in turn, affects auditory perception. Participants performed VT and auditory memory tasks on different days. In the VT task, Japanese participants continuously reported their perception while listening to a Japanese word (2- or 3-mora in length) played repeatedly for 5 min. In the auditory memory task, a different sequence of three morae, e.g., /ka/, /hi/, and /su/, was presented to each ear simultaneously. After some period (0-4 s), participants were visually cued to recall one of the sequences, i.e., in the left or right ear. We found that delayed recall accuracy was negatively correlated with the number of VTs, particularly under 2-mora conditions. This suggests that memory persistence is important for formation and selection of perceptual objects.

Excitation-inhibition balance and auditory multistable perception are correlated with autistic traits and schizotypy in a non-clinical population

Individuals with autism spectrum disorder and individuals with schizophrenia have impaired social and communication skills. They also have altered auditory perception. This study investigated autistic traits and schizotypy in a non-clinical population as well as the excitation-inhibition (EI) balance in different brain regions and their auditory multistable perception. Thirty-four healthy participants were assessed by the Autism-Spectrum Quotient (AQ) and Schizotypal Personality Questionnaire (SPQ). The EI balance was evaluated by measuring the resting-state concentrations of glutamate-glutamine (Glx) and ϒ-aminobutyric acid (GABA) in vivo by using magnetic resonance spectroscopy. To observe the correlation between their traits and perception, we conducted an auditory streaming task and a verbal transformation task, in which participants reported spontaneous perceptual switching while listening to a sound sequence. Their AQ and SPQ scores were positively correlated with the Glx/GABA ratio in the auditory cortex but not in the frontal areas. These scores were negatively correlated with the number of perceptual switches in the verbal transformation task but not in the auditory streaming task. Our results suggest that the EI balance in the auditory cortex and the perceptual formation of speech are involved in autistic traits and schizotypy.