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156 EFFECTS OF EARLY MALTREATMENT AND STRESSperformance in adulthood. However, the Morris water maze is a model of escapelearning that, by definition, involves an aversive component, which provides themotivation for escape. The water maze is an interesting task for the current discussionbecause it provides an opportunity to examine cognitive performance understressful conditions. In sequence, the animal must contend with (1) removal fromthe home cage, (2) transport to the testing area, (3) placement into the pool of water,murky at that, and (4) the uncertainty at each stage of testing. Initially, most animalsbehave in a manner similar to that of an open-field test, circling the perimeterand remaining close to the walls (i.e., thigmotaxis). There is little opportunityfor learning so long as the animal refuses to enter the center area of the swim mazewhere the platform is located. The tendency to remain close to the walls and reluctanceto enter the center area is commonly associated with a fear response tothe environment. Not surprisingly, thigmotaxis is significantly more prevalent inthe offspring of Low compared to High LG-ABN mothers. The difference in thigmotaxisis reversed with postweaning environmental enrichment (Bredy et al.,2003a,b). Moreover, Smythe and colleagues (Smythe et al., 1996, 1998) show thatblockade of hippocampal cholinergic input results in increased fear behavior underconditions of novelty. The effect is blocked with administration of acute benzodiazepine,an anxiety reducer. The offspring of Low LG-ABN mothers showdecreased hippocampal cholinergic innervation, which might well explain theincreased thigmotaxis and thus the impaired performance in the Morris water maze.The hippocampus is also implicated in processing information related to thediscrimination of novelty/familiarity (Habib & Lepage, 2000), and thus the actualnature of the behavioral differences between the offspring of High and LowLG-ABN mothers in settings such as the Morris water maze become difficult todisentangle. Rather than becoming lost in the debate over whether such differencesemerge due to alterations in emotional or cognitive function, which is clearlybeyond resolution at this time, it is probably best to simply restate the findings:The offspring of High and Low LG-ABN mothers differ in hippocampal developmentand plasticity, behavioral responses to novelty, and performance in testsof episodic learning and memory. Although the cause-effect relations embeddedwithin these findings remain to be determined, the important point concerns thepronounced maternal effect on cognitive performance under stressful conditions.Maternal Programming of Attentional SystemsPerformance on tests of object recognition or the Morris water maze also dependson the ability of animals to attend and process relevant stimuli. The medial prefrontalcortex (mPFC) plays a pivotal role in so-called executive functions, in whichinformation is processed on line through working memory. Neurons within themPFC are involved in maintaining task-relevant information “on line” for briefperiods (Fuster, 1997) and subserve processes of working memory and sustainedattention, both essential components for structuring goal-directed behaviors.