Imprinting and cortical plasticity: a comparative review.

Results of research on imprinting and developmental neurobiology of the visual cortex are compared to evaluate the evidence for or against a frequently hypothesized linkage of the two phenomena. The comparison reveals striking similarities. In both paradigms a sensitive period exists. Once this sensitive period is over, the storage of early influences from the environment remains stable throughout life. Storage of "natural" stimuli is facilitated by a certain preorganisation of the receiving brain areas. It is stated that the two phenomena are not directly linked, but are two expressions of a developmental process, which may be common for the organisation of the connectivity of single cells as well as for complex neuronal networks as they are likely to be involved in imprinting. This process is basically self-organizing, but can be influenced by superimposed controls. Differences of the stability of storage of external influences might be explained by the difference in the overall amount of morphological alterations, which is large in the young and small in the adult animal. This holds for both the modifiability in the visual cortex and imprinting.