Genetic approach to variability of memory systems: Analysis of place vs. response learning and Fos‐related expression in hippocampal and striatal areas of C57BL/6 and DBA/2 mice

Abstract

C57 and DBA mice were trained in a crossed maze to assess possible strain differences in place or response learning as a function of training duration (8 or 17 days) and extramaze cueing conditions. The first condition consisted of a diffuse visually cued environment (rich cueing). The second was the same plus an explicit visual cue marking the direction of the baited arm (rich cueing plus cue). The third was a featureless environment (poor cueing). During training, mice were released from the south arm and rewarded in the east arm. Probe trials on which mice were released from the north arm and allowed to choose either the east (place learning) or the west (response learning) arm were given either on the ninth (PT1) or the eighteenth (PT2) days. Strain x context differences in the activation of the dorsal hippocampus and the dorsolateral striatum were examined by analyzing Fos expression following each probe trial. Results first showed that C57 were essentially place-learners, whereas no learning modality was predominant in DBA, except on the PT2 run with the explicit cue available. Examination of Fos expression in C57 trained under "rich cueing" and "rich cueing plus cue" conditions revealed a strong and parallel increase of immunoreactivity in the hippocampus and dorsolateral striatum following PT1 that decreased under PT2. In that strain, the similar time-course variation of Fos expression in both areas suggests a simultaneous involvement of hippocampal- and striatal-based learning mechanisms, even if those controlled by the hippocampus were prevailing on those controlled by the dorsolateral striatum. In DBA mice, however, the absence of any preferential learning modality was associated with 1) a consistent hippocampal activation persistent across probe trials, and 2) a global superior activation of the dorsolateral striatum. Distinct patterns of Fos expression were therefore associated with every strain-specific learning modality. In each strain, however, each modality was found to be remarkably stable, whatever the training duration and the cueing conditions.

Congenic Mouse Strains Enable Discrimination of Genetic Determinants Contributing to Fear and Fear Memory

“…The D2 mice had far lower levels of fear related behaviour compared with B6, which is consistent with this strain having a fear memory deficit. This difference in behaviour is supported by literature indicating differences in hippocampal function and hippocampal protein kinase C (Paylor et al 1993;Bowers et al 1995), brain morphology (Ingram and Corfman 1980), and biochemistry (Fordyce and Wehner 1992;Bowers et al 1995) fos expression (Passino et al 2002) and electrophysiology (Wang and Chow 1994) between the two strains.…”

Enhanced procedural learning following beta-amyloid protein (1-42) infusion in the rat

“…First, in agreement with earlier reports that animal models of AD mainly show performance deficits in hippocampalmediated tasks, our AD rats were incapable to implement place learning following a short training period in the cross maze. However, contrary to rats with hippocampal inactivation [10] or mice with a genetic hippocampal dysfunction [14], that basically show no predominant learning modality under this condition, AD rats exhibited robust response learning. As place learning following short training strongly depends upon the presence of intra-and extra-maze cues, it could be that AD rats do not use, or pay no attention to, such cues thus excluding any possibility to implement allocentric spatial orientation.…”

Multimodal Sensory Integration and Concurrent Navigation Strategies for Spatial Cognition in Real and Artificial Organisms

“…C57BL/6 and DBA/2 mice present significant differences in hippocampal anatomo-functional properties (see Ref. [118], for details). In spatial navigation tasks, C57BL/6 mice tend to be more efficient than DBA/2 mice when (hippocampal-dependent) processing of contextual information is required, whereas DBA/2 mice tend to show better performances in tasks requiring the formation of simple stimulus-response associations.…”

“…In adult mice, the presence of intra-maze and extra-maze cues favors place learning, whereas a poor cueing environment favors stimulus-response learning [see Ref. [118], Fig. (6)].…”

“…Subjects could also count the visited arms either clockwise or counterclockwise, which corresponds to a more automated strategy. In the early phase [118]. (A) Schematic representation of a cross-maze with four identical arms (north, south, east, and west) and transparent Plexiglas high walls fixed on both sides of each arm.…”