Distinguishing Self and Other In High Functioning Autism

Background:

            Rogers and Pennington (1991) proposed autistic subjects may have abnormalities in how they cognitively represent actions performed by the self and by others. Schutz-Bosbach et al. (2005) tested self and other representation in a sample of typically developing (TD) individuals, using the rubber hand illusion. Transcranial magnetic stimulation (TMS) was used to measure brain activity in motor regions when subjects (a) experienced an illusion that a confederates arm belonged to them (self condition), and (b) simply observed a confederates arm (other condition). They found that actions attributed to the self were associated with motor suppression, whilst actions attributed to another led to motor facilitation. This study provides evidence that the motor cortex represents actions attributed to self and other differently.

Objectives:

            The present study applied this paradigm to a sample of high-functioning autistic (HFA) subjects, to determine if they represented actions attributed to the self and other differently. It was expected that autistic subjects would have an atypical pattern of activation in the self and other conditions. Given that TD individuals have been found to have stronger motor activation when attributing an action to another person, it is possible this activity reflects mirror neurons. Thus, two hypotheses were proposed for this study. Firstly, that TD subject’s would demonstrate the same pattern of activity as Schutz-Bosbach et al. (2005) – stronger activity in the ‘other condition’ by comparison to the ‘self condition’. Secondly, that HFA subjects would have reduced or equal levels of activity in the other condition by comparison to the self condition - attributable to a faulty mirror system.

Methods:

            Subjects with a confirmed diagnosis of HFA were compared to TD (N=10 males in each group). All subjects were screened with tests on IQ, executive function, adaptive behavior, developmental history, and the AQ.  An assessment was made by a clinical psychologist as to each subject’s diagnosis or lack of one. Subjects then took part in three conditions; self (illusion elicited), other (illusion not elicited) and a baseline measure. In the self and other conditions, subjects observed the confederates finger making small contractions. In synchrony with the contractions, 20 motor evoked potentials (MEPs) were recorded from the subject’s right index finger.

Results:

            A mixed model ANOVA with group as the between subjects factor (HFAs and TD) and condition (self and other) as the within subjects factor was used for preliminary analyses. TD individuals have demonstrated stronger MEPs in the other condition by comparison to the self condition, whilst HFA subjects have demonstrated stronger MEPs in the self condition by comparison to the other condition. These findings have not reached significance due to an incomplete sample. 

Conclusions:

            Thus far control subjects have demonstrated the hypothesized trend (other condition providing stronger MEPs than self condition), supporting previous research by Schutz-Bosbach et al. (2005). HFA subjects have demonstrated the hypothesized trend (self condition providing stronger MEPs than the other condition), providing evidence of atypical self/other representation, which could be attributable to a disturbed mirror system.