The purpose of this study was to examine how mental disturbance induced by electro-convulsive shock will recover as time elapses.
The subjects studied were mental patients, who were not greatly disturbed and capable of cooperating in test situation.
A total of 24 subjects were used.
Prior to shock, case histories were obtained from each subject in individual interviews. Name, age, birth-place and significant past events were recorded. Electro-convulsive shock was then administered producing a state of unconsciousness. After shock, in order to determine whether or not the subjects were capable of recalling past experiences, we again interviewed them, and tested retention details. Recovery-time was also measured. The latter period refers to the time that the subjects need to correctly respond to the examiner's questions. Recovery speed was calculated by using the inverse number of the recoverer-time.
Eeperimental results were as follows :
After shock treatment, the reflex movement to pain stimulus recovered first, acknowledgement of their names and response to calling followed. Next, recognition of their surroundings, figure perception, and recognition of left and right and up and down recovered.
In due time, distance perception recovered, and about this stage the patients showed recognition of absolute spatial direction. Memory of past experiences also recovered.
All types of visual perception did not recover at the same time, vls. the recovery-period varied according to the difference of visual functions. Fig. 2 shows their course of recovery.
The recovery proceess of life history (events of the past) display notable characteristics, namely older memories recovered more quickly than newer ones.
This is shown in Fig. 1. The abscissa indicates the time-passage from past to pretsent and the ordinate, the recovery-speed. Five typical patients were used for this figure.
To explain the above mentioned results, we proposed a hypothesis of “memory stratum”. We suppose that perception and memory activity, which shows an hierarchical structure, depend on the stratum structure of the cerebral cortex. Self-awareness, such as awareness of the name which formed in childhood is assumed to be localized at the bottom stratum, memory of past events, near the bottom stratum, and perception of the environment, in the upper parts of the cortex. In other words the surface of the cortex represents consciousness of the present, the bottom stratum the self-awareness, and the intermediate stratum, the activity of past memories.
It seems that electric shock disturbes the surface or the upper parts of the cerebral cortex most markedly, while its effect apparently weakens as the bottom stratum is reached. The difference of recovery-speeds substantiates this hypothesis.