How Do Children with and without Autism Perceive the Passage of Time?: fMRI Reveals Differences in Neural Systems Recruited for Time Perception

Background: Identifying the relative function of the primordial interval timing system (in the milliseconds to minutes range) is arguably important in those affected with autism; pathophysiological differences are beginning to be revealed (not only in autism, but related psychological conditions; e.g., schizophrenia, ADHD), and autistic interval timing differences have been found to correspond to certain diagnostic behavioral tendencies. It is generally found that individuals with autism tend to be less precise and more variable when timing relatively longer stimulus durations (e.g., over ~3+ seconds; compared to unaffected individuals). The timing of supra-second durations is well known to recruit cortico-striatal timing mechanisms in adults, but as yet how the autistic brain ‘keeps time’ is unknown. 

Objectives: To-date, there are no existing fMRI studies of interval timing in typical childhood, or in those children affected with autism. In our fMRI study, children (aged 8-13 years) with and without a diagnosis of autism completed a temporal ordinal comparison (time perception) procedure inside the magnet using supra-second durations ranging from 1-11-s.

Methods: During each trial in the temporal ordinal comparison procedure, a pair of stimulus durations (comprising a standard, S; and comparison, C) are presented in quick succession, and children were asked to judge whether C was ‘shorter’ or ‘longer’ than S. There were two versions of the task in which S was either (consistently) 2.2-s or 8.2-s. In both versions, the six C durations were shorter and longer incremental deviants of S (+/-12, 24, 36%). Our a-priori ROI mask included regions typically recruited during adult time perception tasks: the supplementary motor area; the middle frontal and pre-frontal, superior and inferior parietal, and middle and superior temporal gyri; sub-lobar regions (e.g., striatum, thalamus, insula) and cerebellum. 

Results: Data revealing group patterns and differences in neural activation during both S and C durations will be presented across our ROI. One particularly interesting group difference we observed corresponds to the apparent over-engagement of striatal timing mechanisms when those with autism are timing relatively shorter S and C durations—for instance unlike unaffected children, they revealed striatal activity during the 2.2-s but not 8.2-s standard duration; and tended to recruit the striatum across the comparison durations in the 2.2-s version of the task (ranging between 1-3-s). 

Conclusions: Children with autism show different patterns of activity in several brain regions known to be involved in temporal processing (compared to unaffected children), particularly cortico-striatal systems which are recruited (or ‘engaged’) at shorter durations than appears typical. This pattern suggests affected individuals may experience a subjective lengthening of relatively short durations, and/or, a proclivity to engage beat-based timing mechanisms.