Browsing by Subject "Neuroimaging"
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Item Are icons pictures or logographical words? Statistical, behavioral, and neuroimaging measures of semantic interpretations of four types of visual information(2012-05) Huang, Sheng-Cheng; Bias, Randolph G.; Dillon, Andrew; Francisco-Revilla, Luis; Schnyer, David; Sussman, HarveyThis dissertation is composed of three studies that use statistical, behavioral, and neuroimaging methods to investigate Chinese and English speakers’ semantic interpretations of four types of visual information including icons, single Chinese characters, single English words, and pictures. The goal is to examine whether people cognitively process icons as logographical words. By collecting survey data from 211 participants, the first study investigated how differently these four types of visual information can express specific meanings without ambiguity on a quantitative scale. In the second study, 78 subjects participated in a behavioral experiment that measured how fast people could correctly interpret the meaning of these four types of visual information in order to estimate the differences in reaction times needed to process these stimuli. The third study employed functional magnetic resonance imaging (fMRI) with 20 participants selected from the second study to identify brain regions that were needed to process these four types of visual information in order to determine if the same or different neural networks were required to process these stimuli. Findings suggest that 1) similar to pictures, icons are statistically more ambiguous than English words and Chinese characters to convey the immediate semantics of objects and concepts; 2) English words and Chinese characters are more effective and efficient than icons and pictures to convey the immediate semantics of objects and concepts in terms of people’s behavioral responses, and 3) according to the neuroimaging data, icons and pictures require more resources of the brain than texts, and the pattern of neural correlates under the condition of reading icons is different from the condition of reading Chinese characters. In conclusion, icons are not cognitively processed as logographical words like Chinese characters although they both stimulate the semantic system in the brain that is needed for language processing. Chinese characters and English words are more evolved and advanced symbols that are less ambiguous, more efficient and easier for a literate brain to understand, whereas graphical representations of objects and concepts such as icons and pictures do not always provide immediate and unambiguous access to meanings and are prone to various interpretations.Item Functional neuroimaging of morphological processing in nonnative speakers of English(2012-12) Kim, So-Hee, Ph. D.; Meier, Richard P.; Sussman, Harvey M.The nature of morphological processing has been a focus of research in the cognitive neurosciences of language for decades, primarily because the systems underlying simple, word-level linguistic processes may also contribute to fundamental human cognitive capacities and brain functions (e.g., categorization, functional neural organization, and memory). To date, neuroimaging research has yet to demonstrate whether nonnative speakers of a language sort out and process morphologies in the same way that native speakers do. This study, therefore, is intended to identify neural mechanisms that have so far eluded detection. Using functional magnetic resonance imaging, this study adopts an event-related design to investigate the neural responses during English regular and irregular past tense verb generation by Korean nonnative speakers of English. A whole-brain analysis reveals that the processing of irregular verbs evoked greater neural activation than for regular verb processing, and distinctive regional differences of neural responses were found. Specifically, neural activation in regions of the middle and the superior temporal gyri in the right hemisphere was found to be relevant to regular past tense processing, whereas neural recruitment in regions of the inferior frontal gyrus, the supramarginal gyrus, the caudate, and the thalamus in the left hemisphere was found to be significant in irregular past tense processing in nonnative speakers of English. In particular, the results support claims for an inhibitory role of the caudate in prepotent responses and for a thalamic function controlling retrieval of specific items in language and memory. In addition, as reported in earlier studies with native speakers, the results showed increased activity in the frontal cortex and the cingulate cortex bilaterally during both regular and irregular past tense processing. In this study, however, the neural involvement of the cortices in both hemispheres was viewed as evidence for a more general cognitive control function induced by the experimental task rather than by their essential role in morphological processing, since the selective attention required for the rapid past tense generation task would itself entail such cognitive control. Taken together, the results shed further light on the cortical and subcortical representation of language in the human mind and brain.Item Herpes simplex-1 as an additive risk factor for cognitive decline in apolipoprotein E4 carriers(2015-08) Eagan, Danielle Erin; Haley, Andreana P.; Schnyer, David M; Maddox, Todd; Mumford, Jeanette; Sullivan, ChristopherThe identification of early, modifiable risk factors for cognitive decline presents the most promising opportunity for intervention. To date one of the most robustly replicated risk factors for the most common form of dementia, Alzheimer’s disease (AD), is the Apolipoprotein E4 (ApoE4) allele. Risk for sporadic and familial late onset AD increases nearly threefold for each E4 allele an individual carries. However some E4 carriers do not develop cognitive decline, and many non-E4 carriers do, highlighting the role of environmental variables in the progression to clinical symptoms. There is evidence that herpes simplex-1 (HSV-1), a common neurotropic viral infection with affinity for the same brain structures affected in AD, is an acquired risk factor that may compound the genetic risk associated with ApoE4. We examined the interaction between the ApoE4 allele and HSV-1 in cognitively normal middle-aged adults using neuropsychological testing and structural and functional neuroimaging. Neuropsychological assessments were used to determine cognitive differences between groups. Structural neuroimaging was used to measure group differences in bilateral hippocampal volumes, and cortical thickness in brain regions most likely to be affected by AD and HSV-1. Functional neuroimaging was used to examine differences in resting- state brain activity within the default mode network (DMN), a network known for alterations in functional connectivity during the progression from normal aging to AD. With regard to cognition we found that ApoE4 carriers performed significantly lower on tests of executive functioning when they were infected with HSV-1. HSV-1 infection alone also correlated with significantly lower full scale IQ (FSIQ). Within the structural domain we found that individuals with ApoE4 had significantly smaller bilateral hippocampal volumes compared to individuals without the virus, regardless of HSV-1 status. Within the functional domain we failed to find any group differences in functional connectivity within the DMN. Together these findings suggest that HSV-1 may contribute to cognitive changes linked to cognitive vulnerability, and that ApoE4 may contribute to structural brain vulnerability. Because these factors are identifiable prior to the onset of frank cognitive decline, antiviral intervention could be considered as a means of mitigating risk for cognitive decline.Item Neural correlates of emotion regulation : an fMRI study of big picture reappraisal(2013-08) Lantrip, Crystal Marie; Rude, Stephanie Sandra; Allen, Greg, doctor of clinical psychologyCognitive emotion regulation strategies can be used to counter the negative effects of life stress. In neuroimaging paradigms, many different types of reappraisal strategies have been used to promote cognitive coping with impersonal, emotion-evoking stimuli, but limited research has been done utilizing specific reappraisal strategies with real-life events. Big picture reappraisal is a specific emotion regulation strategy that offers a way of managing distress aiming to promote acceptance and cognitive coping. Big picture reappraisal instructions (experimental condition) were compared to distraction and rumination instructions (control conditions) resulting in activation in areas associated with cognitive control (orbital frontal cortex, superior parietal lobe, cerebellum lobule VI). Mood ratings collected after each of several condition prompts were significantly more positive in the distraction compared to the big picture reappraisal condition during the first third of the induction, but as the task progressed the effectiveness of distraction declined considerably. There were no significant condition differences in mood during the second and third segments of the induction.