Abnormal activity patterns in premotor cortex during sequence learning in autistic patients

Abstract

Evidence for frontal abnormality in autism has accumulated in recent years. Our own studies have shown abnormal activation in prefrontal cortex during finger tapping and visuomotor coordination. Studies in healthy adults suggest reduced premotor and increased prefrontal activity during advanced learning stages. We examined hemodynamic changes during visuomotor learning in autistic patients. We studied eight high-functioning autistic patients and eight control subjects during learning of an 8-digit sequence over a period of 8 min, using functional magnetic resonance imaging. Autistic patients showed overall less prefrontal activation during late visuomotor learning; however, the main finding was a complementary one of enhanced activation in right pericentral and premotor cortex. In the autism group, Brodmann areas 3, 4, and 6 of the right hemisphere became more involved during late learning stages (trials 25-48), compared with early stages (trials 1-24). This effect was not seen in the control group. Our findings suggests that in autistic patients 1) primary sensorimotor and premotor cortex, which is normally predominant in early stages of visuomotor learning, plays an atypical role in later stages, even when learning is evident; and 2) handedness and side of execution interact with asymmetry of visuomotor learning activations, contrary to what is seen in normal adults.