The hippocampus plays an important role in the processing of spatial memory. During exploration, theta oscillations (4-12 Hz) are prominent in the hippocampus, whereas during sleep and rest irregular sharp wave/ripple (SWR) events occur spontaneously in the hippocampus and may support memory consolidation. To date, the ventral sub-region of the rodents hippocampus, has received less attention relative to the more accessible dorsal part. It has been suggested that spatial information decreases along the septo-temporal axis in favour of coding salient features and coordinated oscillatory activity might enable the binding of spatial and nonspatial information. The first goal of my research was to investigate how the spatial representation by dorsal and ventral neurons is organised by theta oscillations in the hippocampal network. The second goal was to investigate the role of the ventral hippocampus in spatial learning. Finally, the third goal examined to what extent the firing relationships established during spatial learning are replayed during subsequent sleep in the ventral CA1. I recorded the network activity of dorsal and ventral CA1 in rats performing a spatial memory task on the cheese board maze (Dupret et al., 2010). By using parallel multi-channel extracellular recordings in the dorsal and ventral portions of the hippocampus in behaving rats, I found that dorsal and ventral CA1 were theta coupled at particular times of the spatial learning. High coherence periods across the two regions were characterized by a strong speed-modulation of ventral theta oscillations, which was absent in other conditions. During sleep, it was found that SWR-related activity was presented in the ventral hippocampus as well, when the coordinated population activity established in spatial learning was reactivated within the two sub-regions. By contrast, reactivation across the two regions was observed outside the SWRs epochs. Overall, the data suggests that the ventral hippocampus might be involved in the processing of salient features of the environment such as rewards. On a temporal scale, this non-spatial information might be integrated to the spatial information provided by the dorsal hippocampus during theta oscillation. During sleep/rest periods, the coordinated communication of learned information might underlie the consolidation of memory traces.

Prenatal stress exposure (PNS) has detrimental effects on the offspring’s brain and behaviour and has been identified as an etiological factor in inducing cognitive function deficits in rodents and humans. The neural mechanisms are unclear, however reprogramming of the neuroendocrine stress axis, the hypothalamo-pituitary- adrenal (HPA) axis is hypothesised. A psychosocial stressor (residentintruder paradigm) was used to generate PNS rat offspring, making these studies clinically compatible. The hippocampus and the medial prefrontal cortex (mPFC) are critical in regulating cognitive function and also contribute to the negative feedback control of the HPA axis via corticosteroid receptors, including the mineralocorticoid receptor (MR) and the glucocorticoid receptor (GR). Here the Barnes maze was used to assess spatial learning and memory in male and female PNS offspring during adulthood under different scenarios, including basal and acute and chronic stress conditions. Under basal conditions, PNS was associated with reduced GR and MR mRNA expression in the medial prefrontal cortex (mPFC) and the hippocampus, respectively; suggesting inhibitory feedback control of the HPA axis may be compromised in PNS rats. Moreover, impaired spatial learning was observed in male PNS rats following acute restraint stress. Bilateral lesions of the prelimbic cortex and central administration of an MR antagonist in control rats suggested acute stress-induced learning deficits in PNS males were a result of impaired hippocampus-mediated inhibitory feedback control of the HPA axis. Conversely, a one-week variable stress regimen facilitated spatial learning in PNS rats and this was associated with elevated MR mRNA expression in the dentate gyrus. Moreover, facilitated learning in the PNS rats exposed to chronic stress could be blocked by central administration of an MR antagonist, indicating a facilitatory role of hippocampal MR in spatial learning. In summary, opposite effects of PNS on spatial learning were observed under acute and chronic stress conditions, in which hippocampal MR played a key role in regulating behavioural performance. The effect of age was also examined in PNS rats, and the findings from middle-aged (10-11 months old) rats indicated PNS may accelerate cognitive decline. Sex differences were also studied, with control females’ out-performing males under basal conditions in terms of spatial learning and behavioural flexibility; however following prenatal or chronic stress these sex differences were no longer detected. Furthermore, acute stress impaired spatial learning to a greater extent in females, and this might be attributed to greater HPA axis responses to stress in females compared with males. In conclusion, prenatal stress alters later cognitive performance, in a sex- and stress context-dependent manner. Hippocampal MR plays a critical role in mediating spatial learning, particularly during stress conditions.

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The dual process theory proposes that evaluative conditioning is a form of learning distinct from Pavlovian conditioning and that it displays different functional characteristics such as not being subject to modulation. However, when assessed online as opposed to post-experimentally, modulation of evaluative conditioning by context change has been found in a contingency reversal procedure. Reversal of evaluative learning was found to be faster when trained in a different context rather than in the original training context. The present study addressed the question whether context change or instructions would affect the rate of reversal of evaluative learning and whether reversal learning would accelerate across repetitions. A picture-picture paradigm was used to expose participants to CS-US pairs and contingency was reversed three times during the experiment. Participants were required to provide online causal judgements and valence ratings after each set of 10 training trials. Context change, but not instructions, displayed a trend in affecting reversal of evaluative learning with participants displaying faster learning on trials immediately subsequent to contingency reversal. Instructions affected the reversal of contingency judgements. There was no evidence of acceleration across repetitions for either measure or manipulation.

In episodic recognition memory, differentiation is the assumption that a study item's pre-existing memory trace is updated when additional study for that item is provided. The differentiation models commonly suppose that episodic memory encoding conforms to this process. Although these models have received considerable support within the literature, results inconsistent with their predictions have also been found. The present paper examined conflicting findings that resulted from study list strength manipulations with rhyming word stimuli and semantically related stimuli. As part of the investigation into this discrepancy, 79 university students participated in a computer-based recognition memory task. In this task, word categories of varying length (short vs. long) and word type (rhyming vs. taxonomic) were presented either five times or once within a mixed study list. Following study, an old-new response paradigm was used to examine recognition memory performance. Results from both the rhyming and taxonomic category stimuli were largely consistent with the previous findings in the literature, indicating that word type does appear to influence recognition memory, even within a mixed study list. These findings are interpreted primarily in terms of word type similarity predictions made by one of the differentiation models. Other possible explanations are also discussed.

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No description available.

The dual process theory proposes that evaluative conditioning is a form of learning distinct from Pavlovian conditioning and that it displays different functional characteristics such as not being subject to modulation. However, when assessed online as opposed to post-experimentally, modulation of evaluative conditioning by context change has been found in a contingency reversal procedure. Reversal of evaluative learning was found to be faster when trained in a different context rather than in the original training context. The present study addressed the question whether context change or instructions would affect the rate of reversal of evaluative learning and whether reversal learning would accelerate across repetitions. A picture-picture paradigm was used to expose participants to CS-US pairs and contingency was reversed three times during the experiment. Participants were required to provide online causal judgements and valence ratings after each set of 10 training trials. Context change, but not instructions, displayed a trend in affecting reversal of evaluative learning with participants displaying faster learning on trials immediately subsequent to contingency reversal. Instructions affected the reversal of contingency judgements. There was no evidence of acceleration across repetitions for either measure or manipulation.

Perspective taking, the main cognitive component of empathy, is considered within the psychological literature to be a significant part of human interaction. Despite extensive investigation into the outcomes of this construct, the process by which people take another's psychological point of view has received comparatively little attention. The purpose of this thesis is to investigate in three studies what the individual does when attempting to take the perspective of another person. The first study investigated the particular strategies which individuals use when engaging in perspective-taking behaviours. Dominant themes to emerge from this qualitative assessment of the perspective-taking process were the use of self- (e.g., switching places) and other-information (e.g., targets personal characteristics), of which the former appears to play the central role. Further elements of the perspective-taking process were also identified with the self-information theme. Of these, having experienced a situation similar to that of a target (similar past experience) was found to be a particularly strong aspect of the perspective-taking process and subsequently informed the rationale for the remaining two studies. In view of the findings from Study 1, the second study tested whether past experiences made it easier for participants to take the perspective of another person in a new, but similar situation and the extent to which other aspects, such as switching places with the target, made the perspective-taking process less effortful. Results revealed that similar past experience was the strongest predictor of the ease of the perspective-taking task. Moreover, the extent to which similar past experience increased ease of the perspective-taking process was moderated by the extent to which the participant reflected on that past experience. The final study in this thesis picked up the notion of reflection and examined whether increasing the extent to which an individual engages in self-reflection leads to a concomitant increase in the tendency to take another perspective and the ease with which this can be accomplished. After completion of an intervention program which had a strong focus on self-reflection and understanding of self, there was a noticeable trend for participants to improve on their capacity for self-reflection. The findings also revealed that individuals with a tendency to self-reflect in an insightful and non-ruminative manner demonstrated a similarly high level of general perspective-taking propensity and ease of perspective taking. The studies support the vital role of reflection on similar past experience to that of a target when engaging in perspective taking. This research underscores the importance of examining perspective taking as a process.