Role of the Neocortex in Acquisition of Avoidance Conditioning

Abstract

AFTER a series of experiments which demonstrated that an impairment of maze learning resulting from the ablation of cortical tissue was proportional to the extent of the lesion and not dependent on its location, Lashley¹ postulated that all areas of the neocortex have a general or non-specific function in learning. This he called the mass action effect. Recently, mass action has received convincing support from investigations with cortical spreading depression (refs. 2–4 and unpublished work of R. B. Ross and I. S. Russell, and I. S. Russell, D. Kleinman and H. C. Plotkin), where it has been repeatedly demonstrated that functional hemidecorticated rats require two to four times as many trials as normal animals to learn an escape or avoidance response. The present investigation is an attempt to extend the knowledge of the mass action effect, which, until now, has remained a descriptive phenomenon rather than an explanation of the role of the cortex in behaviour. The hypothesis is that one of the important functions of the neocortex is that it is concerned with the encoding of the information input to the central nervous system. The intertrial interval was used as a means of manipulating this information input.