Assessment of the neurotransmitter dopamine through measurement of the dopamine metabolite homovanillic acid (HVA) in adult subjects with mental retardation and with high rates of body stereotypy (n=12), compulsive behaviors (n=9), or neither (n=12) found lowest HVA concentrations in the stereotypy group and highest in the compulsive group. (DB)

In response to a previous article proposing perceptual reinforcement of stereotyped movements in autistic and mentally retarded persons, it is argued that this theory fails to take into account biological findings and theory regarding pathological stereotyped acts. An alternative theory derived from neurological concepts is suggested. (Author/DB)

Interviews with parents of 30 school-age girls with fragile X syndrome (fraX) and 31 age- and IQ-matched controls concerning autistic behaviors found that girls with fraX had significantly more autistic behaviors than controls, but incidence of autistic behaviors was not correlated with IQ. Anxiety and posterior cerebellar area measures were also…

This analysis of nine young adult males with Down's syndrome found that subjects had great difficulty in completing a skilled motor-perceptual task. Compared to controls, they were much slower, less accurate, and achieved fewer target performances. These behavioral patterns were associated with movement-related brain macropotentials altered in…

Syntactic processing was explored in nine individuals who stutter (IWS). Grammaticality judgments and event-related brain potentials (ERPs) were obtained while participants read sentences, half containing verb-agreement violations, via computer or paper. Judgment accuracy of IWS for the online task, but not offline, was lower, especially for more…