Plasticity and adaptation.
Some of the brain's plasticity is thought to last throughout life. However, children show considerable ability to recover from serious brain trauma. There are studies of children who have had a large part of their cortex surgically removed, usually because of a tumour, and of another person who lived a fairly normal life, even though he was born with most of one hemisphere undeveloped.
There is considerable argument between those who suggest that the cortex is largely undifferentiated, and others, such as Fodor(1), who assert the existence of functional modules. The cortex is certainly not like a filing cabinet, with each memory stored in a neat single location. Notwithstanding studies that show strong activity in certain areas for specified tasks, storage and retrieval of memories seems to involve many diffuse areas at once.
As we have seen, there are certain specialised areas, such as the language units and the sensory and motor cortices. They seem to be generally positioned in the same part of the cortex from one person to another. On the other hand, Lashley(2) showed by experiments with rats that loss of parts of the cortex makes learning in general more difficult. It does not, however, inhibit particular kinds of learning and no particular neural circuits can be found for specific problems.
Bibliography and good reading.
- Fodor, J., (1996),The Modularity of Mind, Cambridge, Massachusetts: MIT Press.
- Lashley, (1929) uncited reference in Gross.R.D., (1987) Psychology: The Science of Mind and Behaviour (p391), Hodder and Stoughton.