Mirror Neuron Dysfunction In High Functioning Autism

Background:

Deficits in the mirror neuron system (neurons which respond to executed and observed actions) have been linked to HFA. It is believed mirror neurons may contribute to the difficulty autistic subjects have understanding other actions and intentions. To date, only an unpublished dissertation by Montgomery (2007) has investigated mirror neuron deficits in communicative gestures (i.e. a waving hand), and no research has investigated directive hand gestures (i.e. a pointing hand) in an autistic sample. Directive hand actions may be important due to the deficit in joint attention (the ability to co-ordinate attention between another person and an object) which pervades all autism spectrum disorders.

Objectives:

            Using functional MRI (fMRI), the present study compared age-matched typically developing (TD) subjects to HFA subjects. Subjects were required to attentively observe four different video tasks while undergoing fMRI. The first and second tasks utilized measures of mirror neuron activity which were hand-object interactions (i.e. a person picking up a mango) and hand-mouth interactions (i.e. a person bringing a banana to their mouth). The third and fourth tasks utilized communicative gestures (i.e. a waving hand) and directive actions (i.e. a hand motioning to stop). This study hypothesized that HFA subjects would demonstrate reduced activity in mirror neuron regions in all tasks by comparison to neurotypicals.

 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.  Further, an assessment was made by a clinical psychologist as to each subject’s diagnosis or lack of one. Subjects were placed in a 3 Tesla MRI scanner where they observed the four different mirror neuron tasks. Following data collection, a blood-oxygen-level-dependent (BOLD) analysis was performed to compare fMRI activity between HFAs and neurotypicals in mirror neuron regions (inferior frontal gyrus & inferior parietal lobule).

Results:

            Data analysis is only preliminary at present; however, HFA subjects have a reduced BOLD response in the inferior frontal gyrus by comparison to TD subjects. In TDs, BOLD activity in the inferior frontal gyrus is stronger for the robust mirror neuron tasks (hand and mouth) than for the social tasks (social and communicative). In HFA subjects the pattern of activity is less clear. Preliminary analyses suggest a small amount of activity in the inferior frontal gyrus for the robust tasks, but activity is near absent in the social and communicative tasks. 

Conclusions:

            On the basis of preliminary analyses this research appears to support the literature that mirror neurons regions are less active in HFA subjects by comparison to controls. Of particular interest, mirror neuron activity seems to be particularly reduced for communicative and directive actions.