REPETITIVE AND TRANSIENT INCREASES IN HIPPOCAMPAL NEURAL CELL-ADHESION MOLECULE POLYSIALYLATION STATE FOLLOWING MULTITRIAL SPATIAL TRAINING

Polysialylated neurons, located at the inner border of the dentate gra nule cell layer, have been demonstrated to exhibit time-dependent chan ge in their frequency at 10-12 h following training in the Morris wate r maze, a spatial learning paradigm. Such a change was not observed in animals required to locate a visible platform or in those rendered am nesic with scopolamine. This frequency response was capable of rapid r eactivation following further training stimuli in a manner that was in dependent of circadian influence. These learning-associated modulation s in neural cell adhesion molecule (NCAM) polysialylation state did no t increase in magnitude despite improved performance, suggesting their activation is required for processing information rather than contrib uting to previously stored, task-associated memory. An increase in NCA M polysialylation appears to be a universal learning response to both spatial and nonspatial paradigms as similar time-dependent changes occ urred following training in a one-trial, step-through, passive avoidan ce response subsequent to water maze training.