HUDSON HOAGLAND 
difficult to see any practical application of psycho-surgery in 
the future, to enable men deliberately to control each other’s 
behaviour in any socially significant way. 
There is however one field which may hold promise for 
constructive purposes. It is possible that agents may be found 
to facilitate learning, memory and recall. It would clearly be 
desirable to find chemical and pharmacological procedures to 
facilitate processes of education, even at the risk of their perver- 
sion for political purposes. 
CHEMICAL FACTORS IN LEARNING, MEMORY AND RECALL 
Experimental work of a variety of investigators, such as the 
classic studies of learning in the rat by Karl Lashley, together 
with clinical observations on man, have shown that specific 
memory traces are not well localized but are diffusely distri- 
buted over extensive brain areas. 
Retrograde amnesia, as seen in Korsakoff’s syndrome, and 
which may also result from head injury, cerebral anoxia, carbon 
monoxide poisoning and electro-shock therapy, indicates basic 
differences in the nature of recent and old memory traces. 
Advancing amnesia extends back gradually in time, obliterating 
memories progressively to more remote episodes, perhaps leav- 
ing only childhood experiences intact. There seems to be no 
relation between the importance of the memory retained and 
its loss. Recent memory, per se, is the more vulnerable, and 
recovery occurs in order of time with the more remote memories 
returning first. 
Recent evidence indicates that there are two quite different 
processes involved in establishing memory traces. There appear 
to be reverberating electrical circuits in patterns of action of 
many neurones in the early stages of the recording of informa- 
tion. Electrophysiological recording shows the presence of this 
kind of activity but this cannot account for the permanent sto- 
rage of the trace. Lorente de N6 has pointed out7 that “Apart 
from the wasteful nature of such a storage mechanism the 
assumption of circulating impulses cannot overcome the diffi- 
culty of explaining how memory can persist after severe shock 
310 
