Strengthening spatial reasoning: elucidating the attentional and neural mechanisms associated with mental rotation skill development

© 2020, The Author(s). Spatial reasoning is a critical skill in many everyday tasks and in science, technology, engineering, and mathematics disciplines. The current study examined how training on mental rotation (a spatial reasoning task) impacts the completeness of an encoded representation and the ability to rotate the representation. We used a multisession, multimethod design with an active control group to determine how mental rotation ability impacts performance for a trained stimulus category and an untrained stimulus category. Participants in the experimental group (n = 18) showed greater improvement than the active control group (n = 18) on the mental rotation tasks. The number of saccades between objects decreased and saccade amplitude increased after training, suggesting that participants in the experimental group encoded more of the object and possibly had more complete mental representations after training. Functional magnetic resonance imaging data revealed distinct neural activation associated with mental rotation, notably in the right motor cortex and right lateral occipital cortex. These brain areas are often associated with rotation and encoding complete representations, respectively. Furthermore, logistic regression revealed that activation in these brain regions during the post-training scan significantly predicted training group assignment. Overall, the current study suggests that effective mental rotation training protocols should aim to improve the encoding and manipulation of mental representations

Anomalous enhancements of low-energy fusion rates in plasmas: the role of ion momentum distributions and inhomogeneous screening

Non-resonant fusion cross-sections significantly higher than corresponding theoretical predictions are observed in low-energy experiments with deuterated matrix target. Models based on thermal effects, electron screening, or quantum-effect dispersion relations have been proposed to explain these anomalous results: none of them appears to satisfactory reproduce the experiments. Velocity distributions are fundamental for the reaction rates and deviations from the Maxwellian limit could play a central role in explaining the enhancement. We examine two effects: an increase of the tail of the target Deuteron momentum distribution due to the Galitskii-Yakimets quantum uncertainty effect, which broadens the energy-momentum relation; and spatial fluctuations of the Debye-H\"{u}ckel radius leading to an effective increase of electron screening. Either effect leads to larger reaction rates especially large at energies below a few keV, reducing the discrepancy between observations and theoretical expectations.Comment: 6 pages, 3 figure

Least squares filtering and testing for geodetic navigation applications

Civil Engineering and Geoscience

The Influence of Long-Term Memory on Working Memory Accuracy

The current research examined if representations in LTM necessarily aid working memory (WM) performance and if increasing interference in LTM limits facilitation from LTM on WM. Remembering multiple objects from the same semantic category can create interference in LTM that may decreases the accessibility of LTM representations during a WM task. In two experiments, participants completed an initial study phase in which objects were categorically (i.e., semantically) related or unrelated. Participants then completed a change detection task that included both previously studied and unstudied objects. In Experiment 1, an object changed into another object from a novel category. We found no evidence of facilitation from LTM on WM performance. However, eye-tracking analyses suggested evidence of facilitation on encoding, through shorter dwell times on studied objects compared to unstudied objects. Furthermore, we found no effect of semantic-relatedness on accuracy or dwell times. Change detection was similarly accurate when the studied objects were all from different categories, as when the studied objects were from the same categories, demonstrating that interference in LTM did not affect WM. In Experiment 2, we attempted to increase reliance on LTM representations by increasing difficulty and interference in the WM task. The changed object on the post-change array came from the same category as the pre-change object. Like in Experiment 1, we did not find any evidence of LTM facilitation on WM performance. Once again, we found shorter dwell times on studied objects compared to unstudied objects. Additionally, as in Experiment 1, there was no effect of interference in LTM on WM performance. Change detection accuracy was similar between semantically-related objects and semantically-unrelated objects. Overall, the results from the current study demonstrate that LTM representations were not used to improve WM performance, but may have been used to facilitate the encoding processes

The Processing of Task-Relevant and Task-Irrelevant Information in Working Memory

Researchers have aimed to better understand the capacity limits and boundaries of working memory (WM) for decades. With a growing body of literature, researchers have started to direct their focus to identifying and understanding specific processes of WM. Information enters WM and is processed differently based on bottom-up (i.e., feature-driven) and top-down (i.e., task-driven) processes. Specifically, the current dissertation aimed to better understand how task-relevant and irrelevant information is maintained, selection, and prioritized in WM. In Chapter 1, we explored how the maintenance of task-relevant information in WM impacts the maintenance of task-irrelevant information. During a hybrid search task, participants were occasionally tested for their memory of distractors in the search array. Results suggest that the amount of task-relevant information maintained in memory does not impact the maintenance of task-irrelevant information. The goal of Chapter 2 was to better understand how information is selected into WM and how task-relevancy and stimulus features impact selection. In a change detection task, participants were presented with arrays containing repeated features and required to search for one type of feature change, while ignoring the other. ERP results confirmed that the task-irrelevant feature was not selected during comparison in WM. Finally, in Chapter 3, the prioritization of information in WM was tested by using a retro-cue change detection task. Here, we reported an unreliable retro-cue effect (RCE) across five experiments. These results suggest that how information and cues are encoded can impact the ability to prioritize task-relevant information. Overall, the current dissertation advances our knowledge of the specific processes involved in WM