Successful Imitation of Atypical Biological Kinematics Following Observational Practice in Autism Spectrum Disorders.

Background: Although sensorimotor processes subserving automatic imitation are operational in autism spectrum disorders (henceforth autism) (Sowden et al., 2016), similar underlying processes function less effectively in a voluntary context where the goal is to observe and imitate biological kinematics performed by a human model (De Myer et al., 1972). This difficulty is suggested to be related to sensorimotor processing activity during direct perception-action matching of biological motion (Stewart et al., 2013). To this end, we used an observational practice (OP) protocol as it enabled the active contribution of the peripheral sensorimotor system during motor execution to be systematically controlled (limited) in an imitation context. Therefore, by controlling this contribution, and based on the automatic imitation work, we expect to show functional movement reproduction of biological kinematics in autism.

Objectives: (1) to examine the direct perception-action matching processes responsible for encoding biological motion during observational practice in autism.

Methods: Twenty autistic (mean age: 25(7); 2 female) and twenty matched non-autistic (mean age: 25(7); 2 female) adults volunteered for the study that was approved by the local ethics committee. Participants completed a 10-trial pre-test where they observed and physically imitated a point-light model displaying typical biological motion with a movement duration of 1700ms. During an observational practice phase, participants performed 30 trials where they only observed a point-light model displaying atypical biological motion with a duration of 1700ms. In a 10-trial post-test, participants were instructed to recall and execute the observed atypical stimulus on each trial. Eye movements were recorded during action-observation. Data for constant error (CE), variable error (VE), and percentage-time-to-peak-hand-velocity (tPHV) were analysed in separate 2 group (autism; control) x 2 phase (pre-test; post-test) mixed design ANOVAs. Percentage-time-to-peak-smooth-eye-velocity (tPSEV) data was submitted to a 2 group (autism; control) x 3 phase (pre-test, early-OP, late-OP) mixed design ANOVA.

Results: Both groups were more accurate at reproducing the observed movement duration following OP (CE: p < 0.05). However, the movements performed by the autism group were more variable (VE: p < 0.05). Importantly, both groups represented the observed atypical biological kinematics with tPHV (p < 0.05) reducing from pre-test (Autism: 41% ± 9; Control: 43% ± 8) to post-test (Autism: 31% ± 7; Control: 30% ± 13). Eye movement behaviour was similar for both groups (p > 0.05).

Conclusions: Although autistic participants performed more variable movements, they imitated the temporal duration of the observed model to a similar level of accuracy as matched-controls. Whilst previous research (Hayes et al., 2016) reported that autistic individuals show attenuated imitation of biological kinematics, the present findings indicated that autistic volunteers observed, encoded and successfully imitated a model displaying atypical biological kinematics following OP. Importantly, this shows that the lower-level perception-action processes responsible for encoding biological kinematics during the action-observation phase of imitation are operational. As the task-specific engagement of the peripheral sensorimotor system was controlled during OP, the aforementioned imitation difficulties in autism are likely to be underpinned by processes engaged to integrate efferent and (re)afferent sensorimotor information during trial-to-trial motor execution.