Dissociation (neuropsychology)

In neuropsychology is meant by a (simple) dissociation which, marked mostly by failure of an isolated neurological (often cognitive ) function made ​​, separation of a neurological process into sub-processes. Some famous cases of Oliver Sacks has described. Thus, there are patients who can not name a household item, if they only see it. Only when they can perceive it with other senses, for example, by touching or sniffing them the designation falls again. The well-studied patient DF has the task to insert a card into a slot, not solve; only when she was told that she should the card " as in a letter box " stuck, it succeeded. From this the conclusion was drawn that there are two separate capacities to assess an orientation (which could not DF ) and on the other hand, an action visually check (which she succeeded ).

A double dissociation (the term goes back to Teuber, 1955) allows the detection of the independence of two different dissociation. This proof is based on two patients ( or patients groups) that different brain damage ( lesions) have suffered and show exactly opposite clinical pictures. While one patient impairments in a task A shows, but can cope with task B difficulty, the other patient shows impairments in task B, but A task can easily tackle. This proves that the two tasks have to be processed by two independently functioning and processes that are localized in different brain areas. About the localization of the lesions conclusions can be closed on the place of processing.

Easier to understand the distinction between single and double dissociation Parkin gives the following example: If the color TV, the color, it can be concluded that the image transmission and the color information are separate processes, but do not have to be fully independent ( simple dissociation, because they can not be independent: it can not turn the image and get the color remain ). If you have two TVs, one with an image fails, the other one has no sound, so it is concluded that these two functions are independent of each other ( double dissociation).

Lately is also spoken in the context of functional imaging of dissociations when distinctly different patterns of activity in different tasks will be found. This type of dissociation is, however, weaker as it refers only to different processes, but whose independence can not be proven.