No abstract

Microbehavioural analysis of the human button-press response in a choice reaction time task enabled us to observe the traditional components of reaction time performance and also several additional indicators of psychomotor organization. The principal finding reported here is that in normal subjects stimulus conditions of varying difficulty differentially affect segments of the button-press response not ordinarily associated with cognitive demands of the task. This observation suggested the presence of a certain interaction between cognitive demands of the task and the subsequent motor output control. In a comparison of normal elderly and demented subjects, we demonstrated that the slower reaction times of the demented represent a virtual psychomotor disintegration. The apparent disintegration is interpreted as an inability of demented subjects properly to prepare, organize, and execute the response. The degree of disintegration is most evident during the motor time, which represents a transition between resting state and actual response completion.