The current study investigated the effects of environmental cues on foraging behavior of Madagascar hissing cockroaches using a maze. By placing the subjects in the maze and have them freely roam around; familiarizing themselves with the maze they gradually spent more time where reinforcement was available. As a mean of measurement, the reinforcers were then removed and the maze was flipped 180 degrees. The results were that the subjects allocated majority of their time in the area of the maze where reinforcers were previously available, and when reinforcers had a different spatial location they went to the location where it had been previously. Implications and limitations are discussed.

Navigating to a previously seen target without vision was unaffected by a 30-sec delay period at the beginning of the walking task. This study investigated whether a 60-sec delay, with or without a cognitive task, would modify the accuracy of reaching an 8-meter target. Thirty young adults participated. The delay, located at 0, 4, or 7 meters, was either to wait, or to count backwards. Kinematic data of distance travelled, distance-to-target, angular deviation, and body rotation from participants’ final position were recorded with a 3-D motion analysis system. Navigation precision was not significantly different with or without a delay, and whether or not the delays contained a cognitive task. However, comparisons among delays revealed a significant effect of delay position with larger distance errors occurring at the 0-meter delay in the 16 participants who walked at least 7 meters, suggesting that a delay at the beginning was more disruptive for navigation accuracy than when it occurred closer to the target.

The work presented in this thesis investigates whether primitive pallial brain circuits such as those found in teleost fish may also encode complex information such as spatial memory despite its circuitry being “simpler” than those found in species with much larger brains such as primates and rodents. Previous behavioral studies have already shown that most teleost fish are capable of spatially orienting themselves and remembering past food locations. Behavioral studies combined with selective brain lesions and related anatomical studies have identified a hippocampal-like region in the fish’s pallium; however, it is unknown whether the neurons located in this structure can also perform cortical-like computations as those found in the mammalian hippocampus. Consequently, this thesis will first present an anatomical characterization of the intrinsic circuitry of this hippocampal-like structure, followed by an in vitro electrophysiological characterization of its constituent neurons. Surprisingly, we have found that this hippocampal-like structure possesses many features reminiscent of the mammalian cortex, including recurrent local connectivity as well as a laminar/columnar-like organization. Furthermore, we have also identified many biophysical properties which would describe these hippocampal-like neurons as sparse coders, including a prominent after-hyperpolarizing potential and an adapting spike threshold with slow recovery. Since this particular dynamic spike threshold mechanism has not been thoroughly characterized in the mammalian hippocampus, we have further investigated the dynamic threshold in the major rodent hippocampal cell types. We have found that only a subset of excitatory neurons displayed this dynamic spike threshold on the time scale that was observed in teleost pallial cells, which allowed us to discuss its potential role in encoding spatial information in both species. Nevertheless, the fact that this teleost hippocampal homologue possesses characteristics that are both akin to the cortex and hippocampus suggest that it may perform computations that, in a mammalian brain, would require both structures and makes this ancestral structure a very interesting candidate to study the mechanism(s) underlying spatial memory.

Visuospatial memory supports cognitive functioning and guides one’s navigation through the environment. Spatial processing allows individuals to remember procedural sequence of steps to achieve a certain goal. It plays a vital role in learning, reasoning, problem solving and language comprehension. Additionally, aerobic fitness enhances cognitive functions such that children that have higher levels of aerobic fitness and motor skills also have better attention, spatial memory, and school achievement. The current study measured spatial memory in children (2nd – 5th grade) to assess developmental differences. Moreover, the study investigated whether spatial memory and running speed were related. It was hypothesized that the data will reconstruct the classic serial position effect and there will be developmental differences in spatial memory performance. Furthermore, participants’ running speed will be negatively associated with their performance on the spatial memory task. That is, the faster their running time, the higher their spatial memory score. Two tasks were presented to children as part of a larger project. The first was a visual-spatial memory task that was presented on a computer using an eye-tracker. The second was a 100-ft shuttle run. Fifty-one children (M age = 104 months, SD = 25.05; 27 female) were introduced to the spatial memory task with a story about a dog walker who lost a puppy. The task had three periods: presentation, retention, and recall. During the presentation period, participants saw the puppy appear in five spatial positions. Next, participants had the opportunity to see all of the positions the puppy visited as teal boxes reappeared in the same locations and remained on the screen for ten seconds. Lastly, during the recall period, participants were asked to recall the order that the puppy visited the five positions. The percentage of correctly recalled items was the dependent measure. A mixed analysis of variance was conducted on percent correct with item position (1st, 2nd, 3rd, 4th, 5th) as a within-subject factor and participant grade (2nd, 3rd, 4th, 5th) as a between-participant factor. There were main effects of sequential position, F(4, 188) = 10.46, p< .001, h2 = .18 and grade, F(1, 47) = 5.32, p= .003, h2 = .25. The extent of serial position effect was comparable across grade levels, with no sign of floor or ceiling effect in any group. Overall, older participants had a higher percentage correct recall than younger participants. Additionally, across grade-levels, first-item primacy and last-item recency effects were apparent. Furthermore, there was a significant association between running speed and spatial memory performance, r= -0.396, p= .004. In summary, the results of the current study suggest that the serial position effect is present by 5-years of age and that children’s memory for spatial locations improves with age. Moreover, children with higher percentages of recalled items on the spatial memory task had faster times on the shuttle run. Future research should consider other measurements of physical activity (e.g., strength, agility, coordination) to see whether physical activity, more broadly, relates to spatial memory performance in children.

The hippocampus is a brain region that can undergo tremendous plasticity in adulthood. The hippocampus is related to the formation of spatial memories in birds and mammals. In birds, plasticity in the hippocampus occurs when formation of such memories is directly relevant to survival or reproduction, such as for breeding or food caching. In reptiles, the homologues to the hippocampus are the dorsal and medial cortices (DC and MC). In several lizard, snake and turtle species, these structures have been related to spatial memory. Experimental investigations indicate that differences in DC volume are related to space use associated with differing foraging ecologies. Differences in MC volume have been associated with territory size-based mate acquisition strategies. Furthermore, territory size has previously been correlated with plasma testosterone (T) levels. Therefore, I hypothesized that neuroplasticity within the MC/DC is controlled by demands on spatial navigation and seasonal differences and that these changes may involve the action of T. During two experimental trials, male Western Fence Lizards (Sceloporus occidentalis) were placed into either large or small semi-natural enclosures and allowed to interact with a female and intruder males over the span of seven weeks. One trial was performed during the spring breeding season and the other during the summer non breeding season, to examine seasonal differences in plasticity. Blood samples were collected at initial time of capture and before sacrifice to measure plasma T. Immunostaining for doublecortin was used to determine the density of immature neurons in each region, and cresyl violet staining allowed for volume measurements of specific regions. MC cell layer neurogenesis was higher in lizards placed in large enclosures than those in small enclosures and higher in the summer than in the spring. DC volume was smaller in lizards held in large enclosures than those in small enclosures. The decreased DC volume seen lizards held in large enclosures may indicate a cost to the increased neurogenesis in the MC of lizards in the same enclosures. These results indicate a possible trade-off between DC volume and MC neurogenesis that allows for switching between the ability to solve novel spatial tasks using the DC while storing a cognitive map in the MC. During the spring, T had no relationship with MC volume, while during the summer this was negative, so effects of T on the MC may be seasonal.

This experiment explored whether a long-term aerobic exercise program may induce significant structural and functional changes in the hippocampus, an area of the brain that is important for spatial navigation and memory formation. Based on existing rodent studies, we hypothesize that exercise will cause a shift to allocentric processing, away from a less robust egocentric learning strategy. It is possible that exercise-induced relief of chronic stress, which contributes to improved hippocampal function, will increase reliance on allocentric spatial navigation. Neurogenesis, which occurs in the dentate gyrus region of the hippocampus, is another indicator of hippocampal function that may influence this shift to allocentric learning. The current study examines whether six weeks of aerobic exercise enhances allocentric processing in healthy young adults. Forty-nine young adults (35 female; age range 18-29 years) were randomly assigned to one of three groups: 1) High intensity interval training group, 2) Moderate intensity training group, or 3) Non-exercising control group. Hippocampus-dependent memory was assessed before and after the intervention on a Virtual Reality Water Maze task, and a high interference memory task, the Mnemonic Similarity Task (MST) which may be dependent on hippocampal neurogenesis. Levels of chronic stress and depression were measured using the Beck Depression Inventory II. It was expected that exercise would improve spatial memory performance on the water maze task, and that performance would improve in proportion to enhanced fitness levels. This improvement in spatial memory performance was expected to correlate with the two indicators of hippocampal function that were assessed in the current study—chronic stress and performance on the high interference memory task. Six weeks of regular aerobic exercise resulted in a 21.5% improvement in spatial memory performance on the water maze task, indicating improved hippocampus-mediated spatial memory function. Improvements displayed by high intensity exercisers were greater than those observed in the moderate intensity exercisers, suggesting that higher intensity exercise may be more effective in enhancing hippocampal function. Importantly, low responders to exercise exhibited a 30% improvement in water maze performance, suggesting that even minor fitness improvements can lead to significant cognitive gains. Chronic stress and depression, and performance on the MST were not significantly associated with changes in spatial memory performance; however trends observed may offer some explanation to the aforementioned changes in spatial memory. Findings from the current study have important implications for treatment options in populations that are currently, or at risk of suffering from impaired hippocampal function. / Thesis / Master of Science (MSc)

No description available.

Yes / Early diagnosis of Alzheimer’s disease (AD) is essential if treatments are to be administered at an earlier point in time before neurons degenerate to a stage beyond repair. In order for early detection to occur tools used to detect the disorder must be sensitive to the earliest of cognitive impairments. Virtual reality (VR) technology offers opportunities to provide products which attempt to mimic daily life situations, as much as is possible, within the computational environment. This may be useful for the detection of cognitive difficulties. We develop a virtual simulation designed to assess visuospatial memory in order to investigate cognitive function in a group of healthy elderly participants and those with a mild cognitive impairment. Participants were required to guide themselves along a virtual path to reach a virtual destination which they were required to remember. The preliminary results indicate that this virtual simulation has the potential to be used for detection of early AD since significant correlations of scores on the virtual environment with existing neuropsychological tests were found. Furthermore, the test discriminated between healthy elderly participants and those with a mild cognitive impairment (MCI).

Sensemaking of large textual information is a cognitively intensive task. Prior work has shown the value of large 2D high-resolution-display spaces in supporting the sensemaking process, by providing a "Space to Think" in which analysts can organize information and externalize their thought process. In this paper, we investigate how analysts use 3D immersive spaces for the same task. To this end, we conducted a user study where participants were asked to solve an intelligence analysis task using an Immersive Space to Think (IST) in a 3D virtual environment using an HMD. The study results show that the concepts of Space to Think extend naturally to 3D immersive space and that the 3D space offers some additional opportunities. With immersive space, analysts i) organized in a surrounding virtual sphere, ii) exploited the depth dimension for encoding relevance, and iii) traded-off between physical navigation and occlusion. / Master of Science / Sensemaking of large textual information is a cognitively intensive task. Prior work has shown the value of large 2D high-resolution-display spaces in supporting the sensemaking process, by providing a "Space to Think" in which analysts can organize information and externalize their thought process. In this paper, we investigate how analysts use 3D immersive spaces for the same task. To this end, we conducted a user study where participants were asked to solve an intelligence analysis task using an Immersive Space to Think (IST) in a 3D virtual environment using an HMD. The study results show that the concepts of Space to Think extend naturally to 3D immersive space and that the 3D space offers some additional opportunities. With immersive space, analysts i) organized in a surrounding virtual sphere, ii) exploited the depth dimension for encoding relevance, and iii) traded-off between physical navigation and occlusion.

Neste projeto investigamos a memória para as informações visual e espacial armazenadas separadamente e de forma conjugada, utilizando o ruído visual dinâmico (RVD) como interferência seletiva. No experimento 1 foi estudado o efeito do (RVD) sobre o desempenho de uma tarefa de memória visual e de memória espacial em situações nas quais essas informações foram apresentadas separadamente. Os resultados mostraram efeito generalizado do RVD em ambas as tarefas de memória, o que levou-nos a questionar a validade da tarefa espacial. No segundo experimento foi realizada uma padronização dos estímulos e parâmetros experimentais desta tarefa. Como esperado, o ruído afetou somente a condição visual. Para verificar o efeito do RVD em uma tarefa de memória para a conjunção visuoespacial foi delineado um terceiro experimento no qual a memória para as características isoladas foi comparada com a memória para a conjunção, sob efeito do ruído. A hipótese era de que se o RVD afetasse a memória espacial em uma tarefa de conjunção visuoespacial, isto seria uma evidência de que aparência visual e posição espacial são armazenados de forma integrada, em uma representação única. Esta hipótese foi confirmada pelos resultados: o ruído afetou a conjunção de informações, independentemente de qual característica (se visual ou espacial) indicava a resposta de rejeição correta na tarefa de reconhecimento da conjunção. Este estudo mostrou evidências de que a memória para a informação isolada é diferente da memória para as informações integradas. Além disto, foi possível demonstrar que uma interferência específica ao armazenador visual (ruído visual dinâmico) afetou a memória para a conjunção visuoespacial. Este resultado é uma evidência de que é formada uma imagem visual da integração visual-espacial. Esta imagem é mantida na consciência, em um sistema que é vulnerável às interferências da percepção, como as ocasionadas pelo ruído visual dinâmico. / In this work we investigate visual and spatial memory information stored separately and combined, using the dynamic visual noise (DVN) as a selective interference. In the experiment 1 we studied the effect of (DVN) on the performance of a visual and spatial memory tasks in situations where these information was presented separately. The results showed an overall DVN effect in both memory tasks, which led us to question the validity of the spatial task. In the second experiment it was performed a standardization of stimuli and experimental parameters of this \"task\". As expected, noise affected only the visual condition. To investigate the DVN effect on a memory task with a visuo-spatial binding it was designed a third experiment in which memory for isolated features was compared with memory binding, under the effect of noise. The hypothesis was that if the DVN affects spatial memory in a visuo-spatial task combination, it would be evidence that the visual appearance and spatial position are stored in an integrated manner in a single representation. This hypothesis was confirmed by the results: the noise affected the binding of information, regardless of what feature (visual or spatial) indicated the rejection response in the task of correct recognition of binding. This study showed that memory for isolated information is different from memory for the integrated information. Moreover, it was demonstrated that a specific interference to the visual cache (dynamic visual noise) affect the memory for the visuo-spatial binding. This result is an evidence that it is formed a visual image of the visuo-spatial binding. This image is maintained in consciousness, in a system that is vulnerable to interference of perception, such as those caused by dynamic visual noise.