Vocate: Luria on PD, cerebroasthenia, oligophrenia

Evidence is then presented on how the directive function of speech is affected in three types of neural disorders: Parkinson's disease, cerebroasthenic syndrome, and oligophrenic children.
The sub-cortical area is damaged in Parkinson's disease, but the cortical motor centers are fully intact. The sub-cortical motor centers' damage causes muscles to exhibit a pathological perseverating tension soon after any initial movement, and thus involuntary action becomes impossible. However, movement can be tied to cortical control by requesting the patient to tap his finger once each time the interviewer says, "Now," and thereby controlled for longer periods. In addition, linking the movement more closely with the patient's speech system by imbuing it with a symbolic function also resulted in the patient demonstrating no difficulty in controlling his execution of movement (finger taps) in response to "How many wheels on a car?" or similar questions.
In cases of cerebroasthenic syndrome, the cortex exhibits a stimulational weakness because neural strength is weakened and equilibrium of the neural processes is impaired. In other words, the cortex itself is in a pathological state, rather than just the sub-cortical processes, as in Parkinson's disease. However, Luria found that the verbal response of a child with this syndrome suffered less than his motor processes. Khomskaya's experiments are presented as evidence that it is the inhibitory or semantic
aspect of speech that is still capable of directing the child's behavior because nonsense syllables or irrelevant utterances had no influence on the child's motor reactions.
The speech system is more drastically affected in cases of oligophrenia. This is a form of deep mental retardation that results from intrauterine or very early childhood damage to the brain, and:
It is particularly characteristic of these children that the dynamics of neural processes underlying speech activity are in their case impaired not less, but more than the dynamics of neural processes which are materialized in simpler sensorimotor reactions. ( Luria, 1959b, p. 458)