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The study examined the effects of lesions of the thalamic nucleus medialis dorsalis (MD) made by neurotoxin in three cohorts ofrats to help understand the contribution of this nucleus to learning and memory. The lesions typically provided comprehensive damage to . MD, while the use of an excitotoxin helped to minimise damage to fibres of passage or adjacent fibre tracts. This excluded one confounding influence that may have been present in some previous studies. Some MD lesions also affected the anterior thalamic nuclei, and this additional damage led to spatial memory impairments, helping to confirm the value of results from rats with lesions confined to MD. Whilst the groups with MD lesions were largely unimpaired on non-spatial tests of visual recognition and discrimination, they were impaired on a configural discrimination task. The MD lesions did not impair spatial nonmatching to sample in aT-maze, nor the acquisition or performance over delay conditions of the standard radial maze task. There were impairments, however, when the radial maze was rotated during the delay, requiring a strategy shift. Similar impairment was found when a matching, rather than non-matching, strategy was required on the T-maze task and also when only some arms were rewarded on the radial arm maze task for reference memory measurement. No impairment was seen when the T-maze matching task was reversed to the non-matching variant, emphasising the lesion rats' preference for preexisting rules. In addition, some evidence was found that MD lesions brought about increased activity, but had no effect on conditioned place preference. The study concludes that MD damage in rats does not directly cause memory deficits. The influence that MD damage has on memory is, however, similar to that associated with damage to prefrontal cortex causing deficits in rule-switching ability, a higher order frontal lobe function.

The primary purpose of the experiments presented in this report was to study systematically the geographic site-name, associative memory of male and female college students (predominantly White and middle class) for locations that varied in distance: local, national, and international sites. In the first experiment, participants were to match listed names of campus buildings and local cities with their marked locations on maps. In the second experiment, under a site-name memory, a site-name/map-aid memory, and a map-aid/name-aid memory (site-name associative memory) condition, participants were to recall or match as many of the 50 US states and the 25 largest US cities as they could. In the third experiment, the participants were to match a listed grouping of the world's largest bodies of water and continents, a set of countries, and the world's largest cities, with their marked locations on maps. In the first experiment, men matched significantly more local cities than did women; in the second experiment, men recalled significantly more of the cities under the site-name/map-aid and the map-aid/name-aid memory conditions than did women; and in the third experiment, men matched significantly more sites on all three maps than did women. The absence of gender differences for campus buildings and states may have been a product of the participants having had extensive opportunities to learn these sites. That men displayed greater knowledge of cities and international sites suggests that they have a greater interest in geography than do women. Because of the limitations of the methodology used, the gender differences favoring men could not be interpreted as primarily a product of nature or of nurture, and thus it was concluded that they were a joint product of nature and nurture.

Some computer users employ large displays, 6 or more monitors, in order to view a large amount of data on a single desktop at one time.  This layout can be useful when the user is performing tasks in which they must view several different information sources at a time.  For example, a user may be writing a paper in which they may be simultaneously typing a document, reading another paper, and view a spreadsheet.  After the task is completed, the user may close all of the windows, however sometime later they may want to view a document associated with that task.  A possible scenario is for the user to know that they were viewing an important document in their top left monitor, but they cannot remember which document.  SpatialHistory looks to allow a user to recall which windows and documents were open at a certain time spatially.  The user may query a particular region of a large display and SpatialHistory will report the windows that were open in that area.  Through a user study, we conclude that i) some users organize their large displays in a spatial manner placing certain types of documents and windows in certain places and that ii) our tool has the potential to help users recall previously viewed windows based on a spatial memory of their desktop. / Master of Science

Conventional theories of diencephalic amnesia have focused on a single thalamic region as a critical factor in the origins of anterograde amnesia. A more contemporary view is that different thalamic regions might contribute in unique ways to normal diencephalic functioning and therefore provide distinct contributions to the learning and memory. This study directly compared the effects of AT and MT lesions on a spatial pattern separation task, a spatial working memory task and a conditioned place preference task. AT lesions but not MT lesions produces deficits on the spatial working memory task on a cheeseboard. No group AT, MT or control rats acquired a conditioned place preference on the AT/MT lesion conditioned place preference task. Furthermore, this study determined the effect of systematic procedural variations on control rats in a conditioned place preference control task. The only variation that acquired a condition place preference was a separate arms conditioned place preference with one pre-exposure and three training trials. The results of this study provide new information regarding the role of thalamic lesions in spatial memory and suggests a revision of the current theories regarding learning and memory to incorporate the thalamic involvement that has been highlighted

APOE ε4 is the major genetic risk factor for Alzheimer’s disease, a dementia characterized by memory impairment and hippocampal atrophy. While associated with episodic impairment and reduced hippocampal volume in healthy aging, APOE ε4 has been related to increased episodic memory performance in young adults. The effect of APOE ε4 on hippocampal volume in young age is uncertain, with studies showing comparable or smaller volumes in ε4 carriers. This thesis aims to further explore the effects of APOE ε4 on episodic memory and hippocampal volume in young adults. In addition to episodic memory, spatial memory will also be assessed, as both these memory types are hippocampus-dependent. Furthermore, potential modulating effects of sex are assessed, as sex differences has been found in relation to APOE-related pathology, episodic and spatial memory and hippocampal volume. Study I examined the effects of APOE ε4 on episodic and spatial memory and hippocampal volume in young adults. Hippocampal volume was assessed by manual tracing of the hippocampal head, body and tail. Study II considered whole-brain structural covariance patterns of the anterior and posterior hippocampus. Furthermore, the association between these patterns and episodic and spatial memory performance was assessed. Study III investigated the effects of APOE ε4 on episodic and spatial memory and hippocampal volume in three different age groups. This was done in order to further explore the different effects of APOE ε4 on cognition and hippocampal volume seen in young and older age. In summary, APOE ε4 was positively associated with spatial function and episodic memory in young adults. Although there were no effects of APOE ε4 on hippocampal volume, structural covariance patterns of the anterior and posterior hippocampus differed as a function of APOE ε4 and sex. Thus, structural covariance may provide an early measure of APOE ε4-related effects on brain structure. Moreover, sex was found to modulate the effects of APOE ε4 to the disadvantage of women. This was seen in both age-related hippocampal volume effects and in structural covariance patterns in young adults, as well as in spatial memory performance across age groups.

Upon acquisition, memories undergo an initial stabilization, or consolidation, process after which they are generally resistant to interference. There is now an abundance of evidence that reactivation or retrieval of a consolidated memory opens up a window of time during which the memory can be strengthened, disrupted, or updated via a process of "reconsolidation". This dissertation is comprised of three experimental studies in rats aimed at investigating previously unexamined aspects of this dynamic memory process. The first study assessed whether spatial memories learned under positively-motivated conditions could be updated with new information following reactivation. Rats that learned a second spatial task in the same environmental context as a previously learned task intruded items from the second episode during recall of the first. This result suggests that the context reactivated the memory for the first task, triggering reconsolidation and updating of the memory. The second study used the memory updating effect obtained in the first study as a behavioral measure to investigate the effects of aging on reconsolidation. Unlike in the young rats, the context reminder did not lead to intrusions of the second learning episode during recall of the first. Older adult human participants in this study also showed a different pattern of results than what had been seen previously in young participants. Therefore, in humans as well as in rats, it appears that aging may lead to changes in spatial memory reconsolidation. The third study piloted an experiment to examine hippocampal network activity associated with the spatial memory reconsolidation task used in the first two studies. Preliminarily, we found that the context reminder manipulation was associated with more place field stability across some spatial tasks and that stability across certain tasks was positively related to our measure of memory updating. Additionally, we found evidence that the context reminder enhanced neural replay of some learning episodes. While preliminary, these results suggest that both place field stability and replay may play roles in this reconsolidation paradigm.

Conventional theories of diencephalic amnesia have focused on a single thalamic region as a critical factor in the origins of anterograde amnesia. A more contemporary view is that different thalamic regions might contribute in unique ways to normal diencephalic functioning and therefore provide distinct contributions to the learning and memory. This study directly compared the effects of AT and MT lesions on a spatial pattern separation task, a spatial working memory task and a conditioned place preference task. AT lesions but not MT lesions produces deficits on the spatial working memory task on a cheeseboard. No group AT, MT or control rats acquired a conditioned place preference on the AT/MT lesion conditioned place preference task. Furthermore, this study determined the effect of systematic procedural variations on control rats in a conditioned place preference control task. The only variation that acquired a condition place preference was a separate arms conditioned place preference with one pre-exposure and three training trials. The results of this study provide new information regarding the role of thalamic lesions in spatial memory and suggests a revision of the current theories regarding learning and memory to incorporate the thalamic involvement that has been highlighted

This study examined individual differences in spatial memory performance in 12-month-old infants using brain electrical activity and walking experience. Greenough's experience-expectant and experience-dependent model of development was used to examine EEG power values among infants with different levels of walking experience (non-walkers, novice, experienced). In accordance with this model, a trend was shown for novice walkers to have higher EEG power values than both non-walkers and experienced walkers only in the central region. Walkers were also found to score higher on an object retrieval (OR) spatial memory task than non-walkers, with amount of walking experience being inconsequential. In addition, infants who scored higher on the OR spatial memory task showed a trend for higher EEG power values in medial frontal, central and parietal areas than infants scoring lower on the OR task. This was not the case for the manual search spatial memory task (AB). There was no interaction among spatial memory performance, walking experience and brain electrical activity. The utility of OR as a spatial memory task that requires the integration of relevant perceptual-motor integration is discussed. / Master of Science