Browsing by Department "Neuroscience"

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Open Access
Effects of HIV infection and cocaine dependence on brain activity during risky and ambiguous decision making
(2017-06-17) Hartley, Bennett
HIV infection can be characterized as a brain disease with 47 percent of infected patients experiencing neurocognitive disorders. MRI studies of HIV patients reveal alterations in gray and white matter. Individuals addicted to stimulant drug use like cocaine are at high risk for engaging in sexual behaviors that contribute to acquisition of HIV. Cocaine dependence and HIV infections each disrupt neural circuits that regulate executive functions involved in decision making. The present study investigated the effects of cocaine dependence and HIV infection on neural activity in response to the valuation of potential gains in the context of unknown and known risks. The study looked at 76 participants across four groups varying in HIV status and cocaine dependence. In an fMRI scanner, participants were presented with pairs of gambles and were required to choose their preference. The behavioral results show that there were no significant differences between groups in their likelihood to select uncertain choices and their reaction times. Imaging results demonstrate increased activation for ambiguous > risky decisions throughout the lingual gyrus and occipital cortex for all four groups. There is bilateral activation in the inferior (IFG) and middle frontal gyrus (MFG) for the control group, which is not seen in either cocaine-dependent or HIV-positive groups. Both cocaine-dependent groups show only left IFG and MFG activity, and the non-cocaine-using HIV-positive group shows no activation in the IFG or MFG. The control group seems overall to have broader activation than the other groups, demonstrated by increased cluster sizes. Analysis of group effects should be conducted to evaluate potential statistical differences between groups.
Open Access
Internal vs. External Attention and the Neurocognitive Processes of Subsequent Memory
(2018-04-25) Abiodun, Folasade
The capacity to store large amounts of information is increasingly relevant in today’s data-saturated society. Two subtypes of our attentional mechanisms are known as internal and external attention, and are respectively characterized by the way we externally attend to relevant sensory information and how we focus inwardly to process and generate mental interpretations of this information. The nature of both external and internal attention and their respective roles in the perception and mental consolidation of sensory information have become integral components of the discussion of learning mechanisms, illustrating the importance of both the initial presentation and subsequent reproduction of stimuli over the course of encoding. We aim to look at the correlation between these two subtypes of attention and successful encoding and retrieval by eliciting steady-state visually evoked potentials (SSVEP) – notable EEG spikes that coincide with the specific frequency of stimuli presentation – during a visual memory task. Improved memory performance was found to increase alongside with image vividness, and SSVEPs were shown to serve as a reliable marker of attentional diversion from external stimuli during internal visualization processes, with greater decreases in SSVEP power corresponding with subsequently remembered words in comparison to forgotten words. Using high temporally resolute EEG, we hope to uncover whether shifts in attentional loci reflect in differences in our memory performance.
Open Access
Potential consequences of adverse lifestyle factors on decision-making as modeled by the Drosophila melanogaster egg-laying process
(2023-04-14) Camacho, Sabrina
Studies have shown that lifestyle factors including impaired gut microbiome health, advanced maternal age, and a diet high in sugar may negatively impact cognitive functioning, but their effects on decision-making have not been thoroughly examined. This study aimed to describe the effects of these three factors on decision-making as well as to determine whether the mechanism behind these effects is metabolic or sensory. This was assessed using Drosophila melanogaster egg-laying chamber assays in which Drosophila were given two choices of substrate on which to lay their eggs: sucrose vs. plain or sucrose vs. sucrose. It was found that neither a reduced gut microbiome nor advanced maternal age influenced decision-making. A high-sugar diet resulted in increased sucrose preference. Neither a metabolic nor a peripheral sensory mechanism explained this phenotype, for ingesting just the nutritious element of sucrose nor just peripheral sensing of the sweet element of sucrose was sufficient to increase sucrose preference. An internal sensory mechanism using Gr43A neurons partially accounted for this phenotype, for the lack of internal sensor activity prevented the unfavorable assessment of sweetness, increasing the perceived value of sucrose. It can be concluded that a diet surpassing healthy sugar levels caused adverse changes in decision-making through a combination of metabolic and sensory mechanisms. This study fills the gap in research about whether lifestyle factors affect decision-making in humans and in Drosophila. The results of this study can be a motivator for people to adopt healthier diets and monitor their sugar intake.