Figure 2.

The relationship between genes, the brain and behaviour. (A) An obsolete view assuming isomorphism between the three levels. (B) A more recent view based on nonlinear relationships. Each gene α, β and χ has several allelic forms that can undergo alternative splicing as shown by the small arrows; genetic cascades are the vertical arrows. The resulting brain modules, A, B and C—consisting of one neuron or a set of neurons—interact as indicated by the vertical arrows. Each module, either alone or in combination with other brain modules, can produce differences in one or more behaviour patterns. The modification in behaviour regulates brain functioning and modulates gene expression, as illustrated by the lower curved arrows.