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Lashley’s concepts of “Mass Action” and “Equipotentiality”
These two inter-related terms were used in opposition to theories based on localization of function.
Lashley conducted experimental studies which suggested to him that the behavioural effects of removing a given amount of neocortex in rats did not depend on where the cortex was removed from. On the other hand he found a correlation between total lesion size and the extent of behavioural deficit. Thus he suggested that the cortex acted as an integrated whole (Mass Action) and that any particular small region of cortex was able to contributed equally towards the performance of a wide variety of tasks (Equipotentiality)
Lashley, K.S. (1929) Brain Mechanisms and Intelligence. University of Chicago Press
Lashley, K.S. (1950) In search of the engram. In Symposia of the Society for Experimental
Biology (No IV): Cambridge University Press.
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