Hypothesis III. Tourette syndrome is only one of several causes of a developmental basal ganglia syndrome

Tourette syndrome (TS) is a hereditary condition characterized by the presence of chronic, multiple motor tics and is commonly associated with obessive-compulsive behavior, attentional and executive dysfunction, and aggressive behavior. A wide range of other genetic and environmental conditions that interfere with normal basal ganglia developmental processes can produce a clinical syndrome that we call the developmental basal ganglia syndrome (DBGS), and which closely resembles TS. Failure to distinguish TS from other causes of DBGS has probably hampered research efforts aimed at clarifying the neurobiological mechanisms, localizing the genetic defect, assessing therapy, and establishing accurate prevalence rates for TS.

Characteristics of children and adolescents with mental retardation and frequent outwardly directed aggressive behavior

Two interrelated cross-sectional studies were conducted to expand earlier findings about correlates of outwardly directed aggressive behavior in children with mental retardation. In Study 1 we compared children with mental retardation, 27 with and 23 without aggression. Aggression was best predicted by concurrent self-injurious behavior (SIB). In Study 2 we examined the likelihood that aggression was predicted by concurrent SIB and other nondestructive maladaptive behaviors in an archival cohort of 701 children younger than 21 with IQs below 70. Self-injurious behavior significantly predicted outwardly directed aggression for all children regardless of age. Additional predictors besides SIB showed only minimal improvements in model R2 values. Results were discussed in light of recent research proposing a common basis for aggression and SIB.

Apparent motion: evidence of the influence of shape, slant, and size on the correspondence process

Four stimulus elements configured as a notional diamond were flashed in pairs to elicit apparent motion. When the elements were identical (4 Zs), the direction of apparent motion was ambiguous. When the elements were pairs of different letters (Cs and Os, Es and Zs), letters of different sizes (Zs and zs), or oppositely oblique lines, the direction of apparent motion tended to be between identical elements. This was true, however, only for an initial, brief observation period. Subsequently, the direction of apparent motion tended to be determined by the direction of motion perceived at first, regardless of the character of the elements. This quickly established directional set (within 10 sec) largely swamped any tendency to resolve correspondence in terms of a feature of the stimulus. It appears to be based on spatial rather than retinal or egocentric coordinates.

Motion aftereffects associated with pursuit eye movements

Contrary to an earlier report [Anstis and Gregory, Q. Jl exp. Psychol. 17, 173-174 (1965)], we find that the sustained retinal motion caused by tracking a moving target over a stationary grating does not result in a motion aftereffect (MAE) which is equivalent to that resulting from comparable retinal motion caused by actual motion of a grating. The MAE associated with tracking generally occurs in elements falling on areas not previously exposed to retinal motion. It is in the same direction as the previous retinal motion in the display and is apparently an induced MAE caused by a weak, below threshold MAE in the elements stimulating areas that were previously exposed to retinal motion. Based on an analysis of eye movement records, we do not believe that the weakness of the tracking MAE is primarily a function of the poor quality of the tracking eye movements. Other possible reasons for the weakness of the MAE are suggested.