MEMORY is thought to consist of overlapping stages. In the first stage the essential process is believed to be the electrical activity of those nerve cells which participate in a learning procedure. In this stage memory can be destroyed by electroconvulsive shock which disrupts this selective electrical activity. The period when memory is vulnerable to electroconvulsive shock in the mammal varies greatly with a minimal value of less than one minute.1
The learning process also leads to changes of a permanent kind so that in man, for example, memory of an event in childhood may persist for life. Thus long-term memory appears to be a relatively stable condition reached as the outcome of events occurring in a period of consolidation. In this period electrical activity is transformed into a more permanent record. Halstead2 in 1951 suggested that the durability of memory may depend upon changes in neuronal nucleoprotein.