ROBERT GALAMBOS 233 



CONCEPTS ABOUT THE BRAIN CHANCJE IN LEARNING^ 



The classical view holds that the neocortex is where the specific changes 

 accountable for new learned responses occur. I shall not list the arguments 

 in favour of this view ; the reader will instead find below several experi- 

 ments that raise objections to this generalization and others that may 

 provide concepts for our possible further enlightenment. 



1. There seems to be no universally accepted definition of learning. 

 'Learning' is common to octopus, cat and bee despite the large differences 

 in their neural apparatus. In particular the mammalian cerebral cortex is 

 obviously not needed since animals wholly deficient m this structure 

 display behaviour that by any reasonable detinition is 'learned'. 



2. Some mammalian habits can be abolished by decortication and then 

 be relearned. The pre- and post-operative CRs seem to be the same, and if 

 we make the plausible assumptitm that the cortex participated in the 

 original habit it is evident that the second one is mediated by extracortical 

 structures. 



3. The cortex, however, is clearly the site of a durable change in certain 

 other kinds of habits. This conclusion emerges, for example, from the 

 learning experiments in which the corpus callosum is sectioned at a 

 crucial state (Myers). These studies show that some essential event does 

 indeed occur in the cerebral hemisphere for habits involving visual 

 discriminations at least. 



4. Different amounts of neocortex seem to be required according to the 

 degree of complexity of the learning problem. If a two-tone pitch 

 discrimination and a three-tone pattern discrimination are taught to a cat, 

 removal of its auditory cortex abolishes both, and only the 'simple' pitch 

 discrimination can be relearned (Neft and Diamond). Some neural events 

 responsible for the 'complex' tone-pattern CR have been eliminated by 

 partial decortication but the necessaries tor a 'simple' CR remain. (What 

 is meant by simple vs. complex learning has not to my knowledge been 

 adequately defined.) 



5. Recent experiments on various neuronal aggregates within the brain 

 (e.g. the reticular and limbic systems), while suggesting remarkably 

 distinctive functions for each of them (e.g. attention, emotion), indicate 

 also that these separate cellular aggregates combine in some orderly way 

 to create the brain change that ultimately yields learned behaviour. 



1 Tliis section closely follows a portion of an unpublished niaiuiscript by R. Cialanibos and 

 C. T. Morgan, 'The Neural Basis of Learning", prepared in iyS7 for Hiiiulhook of Physioloiiy, 

 scheduled for publication in i960. 



