[Neuropsychologic characteristics of children with retarded mental development]

The neuropsychological study of 50 children with the diagnosis of mental retardation permitted to devide them into 2 groups according to the character and severity of disturbances. In the first group disturbances of some cortical functions are of a dynamical character, in the second group there is a stable insufficiency. The prevalence of the defect is different: in the first group phenomena of a dysfunction are observed in the zone of verbal tasks and in the second--in the verbal and nonverbal areas. The consideration of these results from the point of view of the conjugate brain activity allows one to state in the first group a dysfunction of the left (speech) hemisphere along with the normal development of the right hemisphere. In the second group there is a dysfunction of both hemispheres which points to a more expressed severity of disturbances. A special neuropsychological study of the functions of the frontal lobes protecting the highest forms of behaviour regulation demonstrates their different insufficiency in children with mental retardation. The first group shows impulsiveness and instability of an arbitrary control, the second group--enertness, perseveration in programming movements and actions. However, the anomaly of mental development in the second group of children may be related to mental retardation, since the marked defects are compensated by the possibility of holding intentions and capability of purposeful activity.