Application timing of complex magnetic fields delineates windows of posttraining-pretesting vulnerability for spatial...

Male Wistar rats were trained in a two-session-per-day, non-matching-to-sample radial maze task. During the 2 hr interval between training sessions and testing sessions subjects were exposed for 60 min to either sham fields or to a low intensity (200 to 500 nT) electromagnetic (EM) complex pattern whose electrical (current) equivalent has been shown to elicit long-term potentiation (LTP) in hippocampal slices. This pattern was applied either immediately following the training sessions or immediately antecedent to the testing sessions. Exposures to the experimental field immediately following the training session were associated with an impairment in spatial memory as inferred by increased commissions of reference errors. Exposures immediately prior to the testing session were associated with decreased motivation as inferred by a reduction in speed of responding. These results suggest that the timing of the presentation of patterned magnetic fields may differentially affect the representations of habit strength and drive within the consolidating memory trace.