Are specific proteins implicated in the learning process of imprinting?

Day-old chicks were exposed for 0.5 h to overhead lighting ('primed') and then imprinted by exposing them for 90 min to a rotating red box. The chicks were otherwise maintained in darkness. Immediately after training these chicks (n = 16), together with 16 primed and 16 dark-reared controls were killed. Samples from the left cerebral hemisphere were removed including (i) the intermediate and medial part of the hyperstriatum ventrale (IMHV), a region which is crucial for imprinting, (ii) the posterior neostriatum and (iii) the visual Wulst. The samples were incubated with [35S]methionine, processed for SDS slab gel electrophoresis and autoradiographs prepared. The optical densities of various bands were measured 'blind'. For no band was there a significant interaction (ANOVA) between brain region and experience. Optical density was correlated with approach activity during training, a measure of behaviour which correlates with the amount chicks learn. Only for IMHV were correlations significant: a negative correlation (P less than 0.01) for approximately 50 kDa band and positive correlation (P less than 0.001) for an approximately 80 kDa band. These results suggest that associated with training there is a reduction and an increase in the synthesis of proteins in IMHV.