Concluding remarks
The discussion has shown that plasticity in the nervous system is now a topic that is actively investigated by physiologists and psychologists. When I gave the Ferrier Lecture on the subject 25 years ago it was little understood and what was known was mostly about the peripheral nervous system. We now also have a considerable body of knowledge about plasticity in the central nervous system, even in mammals, which is welcome both for its importance in medicine and for our understanding of the fundamental problems of neuroscience. The brain depends upon different channels responding to different items of information, so the key to understanding it is to find out how the channels become connected. The conference has shown that, as in all developmental problems, heredity and environment both play their part. Every aspect of the brain is ‘doubly dependent’, on genetic influences from within and environmental ones from outside. The capacity to respond during development is presumably itself programmed in the genome. Keating showed how adaptive changes are needed in Xenopus to make the receptors and the nervous system keep pace with the changing pattern of behaviour.