Mass Action in Cerebral Function

Abstract

An important speculative discussion arising out of the author''s work on learning in the rat as affected by cortical lesions. The classical concept of specific anatomical localization of function in the cerebral cortex, while satisfactory for certain learned responses, e.g., those involving pattern vision, is completely inadequate for others, e.g., brightness discrimination, maze running. In cases such as the latter function is impaired in proportion to the mass of cortex destroyed quite irrespective of the location of the lesion. The activity of the cortex in such responses is called "mass action." The mass of cortex remaining intact also determines the degree of complexity possible in learned responses of more than one element. Learned responses are believed to be repeated, not through the mediation of identical neurons, but of definite patterns of excitation arising within a homogeneous cellular matrix in the cortex and acting upon motor centers. The nature of the action of a given cortical area, exerted on another cortical area or on subcortical nuclei, may be either (1) production of a preliminary integration, subthreshold for overt responses; or (2) activation of such preliminary set, perhaps with superimposition of additional patterns of excitation. Facilitation of the activity of lower centers by cortical activity may underlie the non-specific relation of cortical areas to the function of such centers.