The role of the frontal cortex in memory: an investigation of the Von Restorff effect

Evidence from neuropsychology and neuroimaging indicate that the pre-frontal cortex (PFC) plays an important role in human memory. Although frontal patients are able to form new memories, these memories appear qualitatively different from those of controls by lacking distinctiveness. Neuroimaging studies of memory indicate activation in the PFC under deep encoding conditions, and under conditions of semantic elaboration. Based on these results, we hypothesize that the PFC enhances memory by extracting differences and commonalities in the studied material. To test this hypothesis, we carried out an experimental investigation to test the relationship between the PFC-dependent factors and semantic factors associated with common and specific features of words. These experiments were performed using Free-Recall of word lists with healthy adults, exploiting the correlation between PFC function and fluid intelligence. As predicted, a correlation was found between fluid intelligence and the Von-Restorff effect (better memory for semantic isolates, e.g., isolate “cat” within category members of “fruit”). Moreover, memory for the semantic isolate was found to depend on the isolate's serial position. The isolate item tends to be recalled first, in comparison to non-isolates, suggesting that the process interacts with short term memory. These results are captured within a computational model of free recall, which includes a PFC mechanism that is sensitive to both commonality and distinctiveness, sustaining a trade-off between the two

Characterizing and Mitigating Transient Noise in LIGO Observatories for Gravitational Wave Detection

The existence of gravitational waves is predicted by Albert Einstein\u27s Theory of General Relativity. Commonly referred to as ripples in spacetime , these waves are generated by some of the most violent and energetic processes in the universe. Despite their theoretical prediction over a century ago, it wasn\u27t until 2015 that the Advanced LIGO (aLIGO) interferometers in Hanford, WA and Livingston, LA directly detected gravitational waves for the first time, confirming Einstein\u27s theory and ushering in a new era of astrophysics. Detecting gravitational waves requires incredible precision. Because of the extreme sensitivity required, it is possible for the gravitational wave data to be contaminated by environmental and instrumental noise. For this reason, characterizing noise that can reduce the sensitivity, and therefore the astrophysical reach, of the detectors is very important. The focus of this dissertation is on characterizing and mitigating transient noise during the aLIGO third and fourth observing runs (O3 and O4, respectively). First, I discuss monitoring the physical environment around the Livingston detector, and how intentionally injecting noise into various parts of the detector tells us about the detector\u27s response to external disturbances, and how noise couples to it. Next, I studied the output of the tool Gravity Spy, which classifies transient noise based on its morphology in the main gravitational wave data channel. Finally, I discuss another study that dives into characterizing and mitigating noise due to a type of light scattering, called Fast Scatter, by studying seismic motion due to trains. In O3, Fast Scatter was the most common transient noise source at Livingston, which is correlated with increases in ground motion in the 1-6 Hz frequency band. Fast Scatter impacted the gravitational wave sensitivity from 10-100 Hz, which is where we are the most sensitive to the mergers of high mass binary black holes. This work identified a location at LLO and which narrow-band seismic frequencies due to trains contributed to increased Fast Scatter noise

Recruitment on Paper, Recruitment on the Web: An Examination of the Rhetorical Strategies used in each Medium

This study examines the rhetoric of college and university recruitment on paper and on the Internet. In particular, the centers on the difference between the two media in relation to their readers, writers, and final texts. A triangulated research approach was used: text analysis, interviews with writers and readers, and reader surveys that include open- and closed-ended questions. The printed and electronic recruitment materials of three peer institutions of the University of Nebraska at Omaha (UNO) formed the basis of the research. Those institutions included the University of Northern Iowa (UNI), the University of Texas at San Antonia (UTSA), and the University of the North Carolina at Charlotte (UNCC). The research revealed that writers of recruitment messages approach their tasks differently, depending on the medium they work in. Printed and electronic text, while essentially the same in content, is presented within the boundaries or possibilities of its medium

A study on the specificity of the association between hippocampal volume and delayed primacy performance in cognitively intact elderly individuals.

Delayed recall at the primacy position (first few items on a list) has been shown to predict cognitive decline in cognitively intact elderly participants, with poorer delayed primacy performance associated with more pronounced generalized cognitive decline during follow-up. We have previously suggested that this association is due to delayed primacy performance indexing memory consolidation, which in turn is thought to depend upon hippocampal function. Here, we test the hypothesis that hippocampal size is associated with delayed primacy performance in cognitively intact elderly individuals. Data were analyzed from a group (N=81) of cognitively intact participants, aged 60 or above. Serial position performance was measured with the Buschke selective reminding test (BSRT). Hippocampal size was automatically measured via MRI, and unbiased voxel-based analyses were also conducted to explore further regional specificity of memory performance. We conducted regression analyses of hippocampus volumes on serial position performance; other predictors included age, family history of Alzheimer's disease (AD), APOE ε4 status, education, and total intracranial volume. Our results collectively suggest that there is a preferential association between hippocampal volume and delayed primacy performance. These findings are consistent with the hypothesis that delayed primacy consolidation is associated with hippocampal size, and shed light on the relationship between delayed primacy performance and generalized cognitive decline in cognitively intact individuals, suggesting that delayed primacy consolidation may serve as a sensitive marker of hippocampal health in these individuals

Sequential Effects in Judgements of Attractiveness: The Influences of Face Race and Sex

In perceptual decision-making, a person’s response on a given trial is influenced by their response on the immediately preceding trial. This sequential effect was initially demonstrated in psychophysical tasks, but has now been found in more complex, real-world judgements. The similarity of the current and previous stimuli determines the nature of the effect, with more similar items producing assimilation in judgements, while less similarity can cause a contrast effect. Previous research found assimilation in ratings of facial attractiveness, and here, we investigated whether this effect is influenced by the social categories of the faces presented. Over three experiments, participants rated the attractiveness of own- (White) and other-race (Chinese) faces of both sexes that appeared successively. Through blocking trials by race (Experiment 1), sex (Experiment 2), or both dimensions (Experiment 3), we could examine how sequential judgements were altered by the salience of different social categories in face sequences. For sequences that varied in sex alone, own-race faces showed significantly less opposite-sex assimilation (male and female faces perceived as dissimilar), while other-race faces showed equal assimilation for opposite- and same-sex sequences (male and female faces were not differentiated). For sequences that varied in race alone, categorisation by race resulted in no opposite-race assimilation for either sex of face (White and Chinese faces perceived as dissimilar). For sequences that varied in both race and sex, same-category assimilation was significantly greater than opposite-category. Our results suggest that the race of a face represents a superordinate category relative to sex. These findings demonstrate the importance of social categories when considering sequential judgements of faces, and also highlight a novel approach for investigating how multiple social dimensions interact during decision-making

Reading Without Words: Eye Movements in the Comprehension of Comic Strips

The study of attention in pictures is mostly limited to individual images. When we ‘read’ a visual narrative (e.g., a comic strip), the pictures have a coherent sequence, but it is not known how this affects attention. In two experiments, we eyetracked participants in order to investigate how disrupting the visual sequence of a comic strip would affect attention. Both when panels were presented one at a time (Experiment 1) and when a sequence was presented all together (Experiment 2), pictures were understood more quickly and with fewer fixations when in their original order. When order was randomised, the same pictures required more attention and additional ‘regressions’. Fixation distributions also differed when the narrative was intact, showing that context affects where we look. This reveals the role of top-down structures when we attend to pictorial information, as well as providing a springboard for applied research into attention within image sequences