Neural cell adhesion molecules, learning, and memory in the domestic chick
The intermediate and medial hyperstriatum ventrale (IMHV) of the chick forebrain is a site of recognition memory for the learning process of imprinting. The results reported here demonstrate that neural cell adhesion molecules (NCAMs) play a time-dependent role in this recognition memory. Dark-reared chicks were trained, tested, and assigned a preference score as a measure of learning. Chicks with high preference scores were designated good learners and those with lower preference scores, poor learners. Controls were untrained. Tissue was removed, 9.5 hr or 24 hr after training, from the left and right IMHV, hyperstriatum accessorium, and posterior neostriatum. Three major NCAM isoforms (180, 140, and 120 kDa) were assayed. At 24 hr only, there was in left IMHV significantly more NCAM (for each isoform) in good learners than in the other 2 groups, and also a significant correlation between the amounts of NCAM and preference scores for all isoforms; the amount predicted by each regression line at preference score 50 (no learning) did not differ significantly from the mean value for untrained controls. There were no learning-related effects in either the hyperstriatum accessorium or the posterior neostriatum.