Dissociation (neuropsychology)
In neuropsychology , a (simple) dissociation is the separation of a neurological process into sub-processes, usually indicated by the failure of an isolated neurological (often cognitive ) function.
Recently, the term dissociation has also been used in connection with functional imaging when clearly different activity patterns are found for different tasks. This type of dissociation is, however, much weaker, since it only points to different processes, but their independence cannot be proven.
Examples
Oliver Sacks has described some famous cases . There are patients who cannot name an everyday object if they only see it. Only when they can perceive it with other senses, for example by touching or sniffing, do they remember the name again. The well-examined patient DF could not solve the task of inserting a card into a slot; only when she was told to put the card "like in a mailbox" did she succeed. From this it was concluded that there are two separate abilities to assess an orientation (which DF could not) and on the other hand to visually control an action (which it did).
Double dissociation
A double dissociation (the term goes back to Teuber, 1955) enables the proof of the independence of two different dissociations. This evidence is based on two patients (or patient groups) who have suffered different brain damage ( lesions ) and show exactly opposite clinical pictures. While one patient shows impairments in task A, but can cope with task B without any problems, the other patient shows impairments in task B, but can cope with task A without any problems. This proves that the two tasks must be processed by two independently functioning processes that are located in different brain areas. The location of the lesions can be used to draw conclusions about the location of the processing.
To make it easier to understand the distinction between single and double dissociation, Parkin gives the following example:
If the color television fails, one can conclude that image transmission and color information are separate processes that do not have to be completely independent (single dissociation, because they cannot be independent: the image cannot fail and the color cannot be preserved). If you have two televisions, one of which has a picture loss and the other has a sound loss, you conclude that these two functions are independent of each other (double dissociation).
See also
swell
- ^ E. Bruce Goldstein: Sensation and Perception. 6th edition. Wadsworth et al., Thomson Learning et al. 2002, ISBN 0-534-63991-7 .
- ^ Alan J. Parkin: Explorations in Cognitive Neuropsychology. Blackwell, Oxford et al. 1996, ISBN 0-631-19472-X .