Biology Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/2749
Browse
3 results
Search Results
Item HOW BILINGUALS' COMPREHENSION OF CODE-SWITCHES INFLUENCES ATTENTION AND MEMORY(2024) Salig, Lauren; Novick, Jared; Slevc, L. Robert; Neuroscience and Cognitive Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Bilinguals sometimes code-switch between their shared languages. While psycholinguistics research has focused on the challenges of comprehending code-switches compared to single-language utterances, bilinguals seem unhindered by code-switching in communication, suggesting benefits that offset the costs. I hypothesize that bilinguals orient their attention to speech content after hearing a code-switch because they draw a pragmatic inference about its meaning. This hypothesis is based on the pragmatic meaningfulness of code-switches, which speakers may use to emphasize information, signal their identity, or ease production difficulties, inter alia. By considering how code-switches may benefit listeners, this research attempts to better align our psycholinguistic understanding of code-switch processing with actual bilingual language use, while also inspiring future work to investigate how diverse language contexts may facilitate learning in educational settings. In this dissertation, I share the results of three pre-registered experiments with Spanish-English bilinguals that evaluate how hearing a code-switch affects attention and memory. Experiment 1a shows that code-switches increase bilinguals’ self-reported attention to speech content and improve memory for that information, compared to single-language equivalents. Experiment 1b demonstrates that this effect requires bilingual experience, as English-speaking monolinguals did not demonstrate increased attention upon hearing a code-switch. Experiment 2 attempts to replicate these results and establish the time course of the attentional effect using an EEG measure previously associated with attentional engagement (alpha power). However, I conclude that alpha power was not a valid measure of attention to speech content in this experiment. In Experiment 3, bilinguals again showed better memory for information heard in a code-switched context, with a larger benefit for those with more code-switching experience and when listeners believed the code-switches were natural (as opposed to inserted randomly, removing the element of speaker choice). This suggests that the memory benefit comes from drawing a pragmatic inference, which likely requires prior code-switching experience and a belief in code-switches’ communicative purpose. These experiments establish that bilingual listeners derive attentional and memory benefits from ecologically valid code-switches—challenging a simplistic interpretation of the traditional finding of “costs.” Further, these findings motivate future applied work assessing if/how code-switches might benefit learning in educational contexts.Item INTERACTIONS BETWEEN APPETITIVE AND AVERSIVE PROCESSING DURING PERCEPTION AND ATTENTION(2017) Padmala, Srikanth; Pessoa, Luiz; Neuroscience and Cognitive Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Although understanding brain mechanisms of appetitive-aversive interactions is relevant to our daily lives and has potential clinical relevance, our knowledge about these brain mechanisms is rudimentary. To address this gap in the literature, we conducted two functional MRI studies that investigated appetitive-aversive interactions during perception and attention in healthy adult human brain. In the first study, we probed how potential reward signaled by advance cues altered aversive distractor processing during a subsequent visual task. Behaviorally, the deleterious influence of aversive stimuli on task performance was reduced during the reward compared to no-reward condition. In the brain, at the task phase, paralleling the observed behavioral pattern, significant interactions were observed in the anterior insula and dorsal anterior cingulate cortex, such that responses during the negative (vs. neutral) condition were reduced during the reward compared to no-reward condition. Notably, negative distractor processing in the amygdala appeared to be independent of the reward manipulation. During the initial cue phase, we observed increased reward-related responses in the ventral striatum, which were correlated with behavioral interference scores at the subsequent task phase, revealing that participants with increased reward-related responses exhibited a greater behavioral benefit of reward in reducing the adverse effect of negative images. Furthermore, the ventral striatum exhibited stronger functional connectivity with fronto-parietal regions important for attentional control. These findings contribute to the understanding of how potential reward influences attentional control and reduces negative distractor processing in the human brain. In the second study, we investigated brain mechanisms underlying the joint processing of positive and negative emotional information during a passive viewing task. Specifically we focused on probing the pattern of appetitive-aversive interactions in brain regions sensitive to the valence and salience of emotional stimuli. In a subset of regions that were sensitive to stimulus valence, competitive interaction patterns were observed. Notably, in other valence-coding regions such as the ventro-medial prefrontal cortex no evidence for competitive interactions was detected. Conversely, in regions sensitive to salience, cooperative interaction patterns were observed. The findings of competitive and cooperative type interactions supported contextual modulation of emotional processing in the human brain.Item The effect of mental stress on brain dynamics and performance related to attention control during a vigilance task: An electroencephalographic investigation(2013) Russell, Bartlett Anne Healy; Hatfield, Bradley D; Neuroscience and Cognitive Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Anxiety can increase distractibility and undermine the quality of psychomotor performance. Models of attention processing postulate that anxiety consumes limited executive resources necessary for maintaining goal-oriented, "top-down" attention control and suppressing stimulus-driven "bottom-up" distraction. Attention Control Theory (ACT) predicts that anxiety adversely affects the efficiency, and particularly inhibitory components of executive, frontally mediated top-down attention control. We used two approaches for examining this model. First, though attention affects synchrony among neural structures, information regarding how human oscillatory patterns (measured with electroencephalography, EEG) change as state anxiety increases is limited. Second, while anxiety affects the balance between top-down and bottom-up mechanisms, to our knowledge no one has yet measured anxiety's effect on attention using a neural measure of top-down control in conjunction with more traditional bottom-up measures of attention capture (e.g., the P3 event related potential, or ERP). Purpose: Study 1 examines the oscillatory patterns (spectral dynamics) of the cortex in order to investigate whether frontal regions exhibit patterns of reduced efficiency and altered networking with posterior regions during threat of shock. In order to assess the relationship between top-down and bottom-up attention dynamics, Study 2 uses the same threat protocol to measure attention-directed top-down modulation of sensory signaling (steady-state visual evoked potential, or ssVEP modulation) and of bottom-up attention capture by discrete targets and distractors (Event Related Potentials, ERPs). Results: The spectral analyses in Study 1 suggest decreased processing efficiency and decreased frontal networking (coherence) with more posterior regions as anxiety increased. Reduced coherence, however, could indicate either increased or decreased top-down focus; Study 2 provides more insight. Neural responses to task-relevant targets (ERPs) diminished as threat increased, while responses to task-irrelevant distractors remained unchanged. Contrary to what ACT would predict, we observed an increase in attention modulation of an ssVEP frequency associated with amplifying the task-relevant signal and no change in an ssVEP associated with inhibiting task-irrelevant stimuli. These findings suggest top-down attention control increased under threat, but was not enough to prevent degraded processing of task-relevant targets coincident with reduced efficiency on task performance. Implications and suggestions for refining ACT are discussed.