Department of Psychology
Permanent URI for this collection
This collection contains research from members of the Department of Psychology at George Mason University.
Browse
Browsing Department of Psychology by Subject "Memory"
Now showing 1 - 2 of 2
Results Per Page
Sort Options
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.