Brain Function

This symposium on memory mechanisms did not stay as close to the relation between nucleic acid biochemistry and learning as its title and Magoun's excellent introduction might imply. Ribonucleic acids and the hippocampus hold joint sway. It is a questionable assumption that, in terms of known biochemistry, RNA has to be implicated to account for the stability of the trace. On one hand the argument taken one step further must implicate DNA-but then experience causes CNS mutations or teaches nothing that is not already in the genes! On the other hand, antibody-antigen, acid-base, or some type of triggered macromolecular interaction could well give products virtually incapable of enzymic degradation while having profound effects on patterns of ion fluxes. Nonetheless, the possibilities of growth processes at situation-specified neuro-anatomical loci, or even of experiential information coded in RNA structure, are well worth considering, and reviews of the genetic code (Nirenberg), CNS ultrastructure (Palay), and neural tissue culture electrical activity (Hild) provided a biophysical background against which activity and learning in specific systems were discussed. Long-lasting changes of electrical activity in ganglia (Luco for the cockroach) and the estimation of RNA concentrations and base ratios (Hyden; Kogan) have since 1962 become more adequately related to learning paradigms rather than mere neural activity. Planarian activity (John) and cerebral "mirror focus" changes (Morrell) have been subject to controversy and reinterpretation. In a novel and increasingly popular field, the ebb and flow of evidence and ideas during two or more years' further work must be expected to seriously outdate such delayed publications. Results of lesions and of electrical stimulation and recording were described by Feindel, Brazier, and Victor in man and in other species by Adey and Weiskrantz. They emphasized the importance of temporal paleoand neocortex in the active integration of past cognitive and emotional experience in its influence on future behavioral expression, which is not to say that these regions are the site of memory storage, especially in the case of limited perceptual or motor functions. Divisions of function were suggested, such as "read-in" lying ventrally in periamygdaloid tissue and "read-out" requiring the nondominant lateral cortex. The major areas and connections cited pointed up a system involving inputs from the amygdala and elsewhere to dorsomedial thalamic nuclei and frontal cortex, which in turn lead via the caudate and cingulum to the dorsal hippocampus, with output subcortically via the hippocampal gyri, or at least not via the fornices. Throughout the book it is apparent that critical attention must be paid to species differences and to the fullest possible psychological analysis of performance changes, as well as to the physiological, anatomical, and