General insight into the frequency and gravity of cognitive dysfunctions following stroke and its influencing factors is still lacking. With an extensive neuropsychological battery 229 patients who had suffered a stroke were assessed. More than 70% of the patients showed a marked slowness of information processing, whereas at least 40% of all patients had difficulty with memory, visuospatial and constructive tasks, language skills, and arithmetic. A significant effect was found for side and type of stroke, gender, and the presence of aphasia. No significant effect was found for cortical versus subcortical lesions, having one versus multiple strokes, having lowered consciousness on admission, the presence of risk factors, a paresis of the hand, or the interval between the stroke and the neuropsychological assessment.

The aim of the present study is to gain more insight into the mechanisms underlying mental practice. The question of whether a totally novel movement may be learned by mental practice was investigated. Healthy young adults had to learn the abduction of the big toe (dominant right foot) without moving the other toes or the foot. The subjects were divided into two groups: subjects who were absolutely unable to abduct their big toe ("absolute zero" group) and subjects who were able to abduct their toe to some extent but showed clear room for improvement ("already doing it" group). Two separate experiments were executed. In the first experiment, 37 absolute-zero subjects had to practice, mentally or physically, the target movement. In the second experiment 40 already-doing-it subjects had to improve their toe-abduction skill. The results showed that absolute-zero subjects could not acquire the toe-abduction movement by means of mental practice. Only subjects who physically practiced the target movement improved significantly. Subjects who had some experience in the task (already-doing-it subjects) improved significantly after mental practice as well as after physical practice. The results seem to indicate that it is more plausible to explain the learning effects of mental practice in terms of a "top-down" mechanism based on the activation of a central representation of the movement than in terms of a peripheral "bottom-up" mechanism based on the activation of muscles.

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