Department of Psychology
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This collection contains research from members of the Department of Psychology at George Mason University.
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Item Who is Most Vulnerable to Social Rejection? The Toxic Combination of Low Self-Esteem and Lack of Negative Emotion Differentiation on Neural Responses to Rejection(Public Library of Science, 2014-03-04) Kashdan, Todd B.; DeWall, C. Nathan; Masten, Carrie L.; Pond, Richard S., Jr.; Powell, Caitlin; Combs, David; Schurtz, David R.; Farmer, Antonina S.People have a fundamental need to belong that, when satisfied, is associated with mental and physical well-being. The current investigation examined what happens when the need to belong is thwarted—and how individual differences in self-esteem and emotion differentiation modulate neural responses to social rejection. We hypothesized that low self-esteem would predict heightened activation in distress-related neural responses during a social rejection manipulation, but that this relationship would be moderated by negative emotion differentiation—defined as adeptness at using discrete negative emotion categories to capture one's felt experience. Combining daily diary and neuroimaging methodologies, the current study showed that low self-esteem and low negative emotion differentiation represented a toxic combination that was associated with stronger activation during social rejection (versus social inclusion) in the dorsal anterior cingulate cortex and anterior insula—two regions previously shown to index social distress. In contrast, individuals with greater negative emotion differentiation did not show stronger activation in these regions, regardless of their level of self-esteem; fitting with prior evidence that negative emotion differentiation confers equanimity in emotionally upsetting situations.Item Passive listening to preferred motor tempo modulates corticospinal excitability(Frontiers Media, 2014-04-24) Michaelis, Kelly; Wiener, Martin; Thompson, James C.Rhythms are an essential characteristic of our lives, and auditory-motor coupling affects a variety of behaviors. Previous research has shown that the neural regions associated with motor system processing are coupled to perceptual rhythmic and melodic processing such that the perception of rhythmic stimuli can entrain motor system responses. However, the degree to which individual preference modulates the motor system is unknown. Recent work has shown that passively listening to metrically strong rhythms increases corticospinal excitability, as indicated by transcranial magnetic stimulation (TMS). Furthermore, this effect is modulated by high-groove music, or music that inspires movement, while neuroimaging evidence suggests that premotor activity increases with tempos occurring within a preferred tempo (PT) category. PT refers to the rate of a hypothetical endogenous oscillator that may be indicated by spontaneous motor tempo (SMT) and preferred perceptual tempo (PPT) measurements. The present study investigated whether listening to a rhythm at an individual’s PT preferentially modulates motor system excitability. SMT was obtained in human participants through a tapping task in which subjects were asked to tap a response key at their most comfortable rate. Subjects listened a 10-beat tone sequence at 11 log-spaced tempos and rated their preference for each (PPT). We found that SMT and PPT measurements were correlated, indicating that preferred and produced tempos occurred at a similar rate. Crucially, single-pulse TMS delivered to left M1 during PPT judgments revealed that corticospinal excitability, measured by motor-evoked potentials (MEPs), was modulated by tempos traveling closer to individual PT. However, the specific nature of this modulation differed across individuals, with some exhibiting an increase in excitability around PT and others exhibiting a decrease. These findings suggest that auditory-motor coupling induced by rhythms is preferentially modulated by rhythms occurring at a preferred rate, and that individual differences can alter the nature of this coupling.Item Spatial memory deficits in a mouse model of late-onset Alzheimer’s disease are caused by zinc supplementation and correlate with amyloid-beta levels(Frontiers Media, 2014-10-22) Flinn, Jane M.; Bozzelli, P. Lorenzo; Adlard, Paul A.; Railey, Angela M.Much of the research in Alzheimer’s disease (AD) that uses mouse models focuses on the early-onset form of the disease, which accounts for less than 5% of cases. In contrast, this study used a late-onset AD model to examine the interaction between increased dietary zinc (Zn) and the apolipoprotein E (ApoE) gene. ApoE ε4 is overrepresented in late-onset AD and enhances Zn binding to amyloid-β (Aβ). This study sought to determine if elevated dietary Zn would impair spatial memory in CRND8 mice (CRND8), as well as mice who carry both the mutated human amyloid precursor protein (APP) and ApoE ε4 genes (CRND8/E4). Mice were provided with either lab tap water or water enhanced with 10 ppm Zn (ZnCO3) for 4 months. At 6 months of age, spatial memory was measured by the Barnes maze. CRND8 mice exhibited significant memory deficits compared to WT mice, as shown by an increased latency to reach the escape box. For the CRND8/E4, but not the CRND8 mice, those given Zn water made significantly more errors than those on lab water. During the probe trial for the WT group, those on Zn water spent significantly less time in the target quadrant than those on lab water. These data suggest that increased dietary Zn can significantly impair spatial memory in CRND8/E4. WT mice given Zn water were also impaired on the 24-h probe trial when compared to lab water WTs. Within the CRND8/E4 group only, levels of soluble Aβ were significantly correlated with average primary latencies. Within the Zn-treated CRND8/E4 group, there was a significant correlation between insoluble Aβ and average primary errors. Levels of the zinc transporter 3, ZnT3, were negatively correlated with soluble Aβ (p < 0.01). These findings are particularly relevant because increased intake of dietary supplements, such as Zn, are common in the elderly—a population already at risk for AD. Given the effects observed in the CRND8/E4 mice, ApoE status should be taken into consideration when evaluating the efficacy of therapies targeting metals.Item Continuous Carryover of Temporal Context Dissociates Response Bias from Perceptual Influence for Duration(Public Library of Science, 2014-06-25) Wiener, Martin; Thompson, James C.; Coslett, H. BranchRecent experimental evidence suggests that the perception of temporal intervals is influenced by the temporal context in which they are presented. A longstanding example is the time-order-error, wherein the perception of two intervals relative to one another is influenced by the order in which they are presented. Here, we test whether the perception of temporal intervals in an absolute judgment task is influenced by the preceding temporal context. Human subjects participated in a temporal bisection task with no anchor durations (partition method). Intervals were demarcated by a Gaussian blob (visual condition) or burst of white noise (auditory condition) that persisted for one of seven logarithmically spaced sub-second intervals. Crucially, the order in which stimuli were presented was first-order counterbalanced, allowing us to measure the carryover effect of every successive combination of intervals. The results demonstrated a number of distinct findings. First, the perception of each interval was biased by the prior response, such that each interval was judged similarly to the preceding trial. Second, the perception of each interval was also influenced by the prior interval, such that perceived duration shifted away from the preceding interval. Additionally, the effect of decision bias was larger for visual intervals, whereas auditory intervals engendered greater perceptual carryover. We quantified these effects by designing a biologically-inspired computational model that measures noisy representations of time against an adaptive memory prior while simultaneously accounting for uncertainty, consistent with a Bayesian heuristic. We found that our model could account for all of the effects observed in human data. Additionally, our model could only accommodate both carryover effects when uncertainty and memory were calculated separately, suggesting separate neural representations for each. These findings demonstrate that time is susceptible to similar carryover effects as other basic stimulus attributes, and that the brain rapidly adapts to temporal context.Item The Effect of Zinc and Zinc Plus Copper on Memory(2009-07-16T15:20:33Z) Perez-Casillas, TizocTrace metals exist in low quantities in the human body. Zinc and copper are two trace metals that are essential in the body, yet they must be balanced; otherwise, negative side effects emerge. Zinc has an antagonistic effect on copper, in that an excess amount of zinc absorbed by the body causes a copper deficiency. Furthermore, previous studies have also shown that exposing rats to zinc given both prenatally to the mother and after birth leads to cognitive impairments in adult rats and increased levels of zinc in the rat temporal cortex and hippocampus, which can be rescued in part by adding copper to the diet (Flinn et al., 2005). This experiment examined the effect of giving zinc and zinc plus copper to adult rats in the drinking water. I raised forty-five rats on zinc (15), zinc plus copper (15), and lab water (15). Zinc and zinc plus copper were dissolved in the rats’ drinking water. The group of rats that had no metals added in the water was measured as a baseline (control). Previous experiments have shown that rats raised on zinc could not learn to extinguish a learned fear. The rats in this experiment were subjected to a fear-conditioning task, and I measured the duration of time to extinguish the learned fear. When dosed with zinc, the rats took the longest to extinguish the learned fear when a stimulus was no longer fearful. Since copper partly remediates the zinc effects, the rats dosed with zinc plus copper extinguished faster than the rats dosed solely with zinc and, in some cases, extinguished faster than the rats dosed exclusively on lab water. This experiment further elucidates the effects of zinc on cognitive abilities and the remediation of zinc’s effects when copper is present. From a larger perspective, this study emphasizes that an excess of indispensable minerals and nutrients, which are found in several food products, does not necessarily imply better human functioning.