Biology
Permanent URI for this communityhttp://hdl.handle.net/1903/11810
Browse
15 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 EEG EFFECTS OF EVENT MODELS IN STORY COMPREHENSION(2023) Rickles, Ben Bogart; Bolger, Donald J; Neuroscience and Cognitive Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Cognitive models can offer deep insights into how stories are comprehended. Models which follow event segmentation theory (EST) focus on the processing of brief episodes or events within a narrative and the boundaries between events. To test the brain mechanisms proposed by EST to occur at the event boundaries we looked at electroencephalographs (EEG) recorded from 49 participants as they were tasked with both listening to and recalling 9 blocks of ~ 6 minute-long audio clips in one of three conditions: single ordered stories, unrelated events from unrelated stories, or single stories in scrambled order. All stimuli were designed to contain event boundaries spaced at semi-regular intervals. Accuracy during an inference recognition task administered after each block was highest in the single ordered stories condition. Analysis 1 examined the effects of event boundary vs. local semantic context on evoked negativities (N400) related to lexical processing of each word. Effects of condition suggest that narrative structure affected lexical processing, more so than event-level structure and sentence-level semantic context. Analysis 2 Examined changes in alpha (8.5-12.5 Hz) and theta (4-8 Hz) band power of the EEG induced by the onset of the event boundary. Boundary-induced changes in both frequencies were recorded, in all conditions. The largest increases were recorded during the ordered stories over large portions of the scalp. How these findings relate to cognitive mechanisms suggested by event segmentation theory is discussed.Item BRAIN BASIS OF HUMAN SOCIAL INTERACTION: NEUROCOGNITIVE FUNCTIONS AND META-ANALYSIS(2023) Merchant, Junaid Salim; Redcay, Elizabeth; Neuroscience and Cognitive Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Social interactions, or the reciprocal exchange between socially engaged individuals, plays a central role in shaping human life. Social interactions are fundamental for neurocognitive development, and a key factor contributing to mental and physical health. Despite their importance, research investigating the neurocognitive systems associated with human social interaction is relatively new. Human neuroimaging research has traditionally used approaches that separate the individual from social contexts, thereby limiting the ability to examine brain systems underlying interactive social behavior. More recent work has begun incorporating real-time social contexts, and have implicated an extended network of brain regions associated with social interaction. However, open questions remain about the neurocognitive processes that are critical for social interactions and the brain systems that are commonly engaged. The current dissertation aims to address these gaps in our understanding through a set of studies using computational and data-driven approaches. Study 1 examined the relationship between social interaction and mentalizing, which is the ability to infer the mental states of others that is considered to be critically important for social interactions. Prior work has demonstrated that mentalizing and social interaction elicit brain activity spatially overlapping areas, but spatial overlap is not necessarily indicative of a common underlying process. Thus, Study 1 utilized multivariate approaches to examine the similarity of brain activity patterns associated with mentalizing outside of social contexts and when interacting with a peer (regardless of mentalizing) as a means for inferring a functional relationship between the two. Study 2 investigated brain regions commonly engaged across social interactive contexts using coordinate-based meta-analysis, which is an approach for aggregating findings across neuroimaging literature. This involved an exhaustive search strategy to find fMRI and PET studies that utilize social interactive approaches, and calculated spatial convergence across studies as a means to uncover brain regions that are reliably implicated during social interaction. The results from Studies 1 and 2 offer major advancements for a neuroscientific understanding of social interaction by demonstrating a functional link with mentalizing and through elucidating brain systems that are commonly reported in studies using social interactive approaches.Item Development of Motivational Influences on Monitoring and Control Recruitment in the Context of Proactive and Reactive Control in Adolescent Males(2020) Bowers, Maureen; Fox, Nathan A; Neuroscience and Cognitive Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Adolescence and the onset of puberty is a time period of physiological and behavioral changes that include a heightened reward sensitivity, but underdeveloped cognitive control. Cognitive control involves monitoring for salient stimuli and recruiting control to adapt behavior advantageously to reach a specific goal and is supported by the three domains of executive functioning (EF): inhibitory control, set-shifting, and working memory. Proactive control is engaged after an informative cue in preparation for an upcoming stimulus, while reactive control can be employed when preparation is not possible and you need to respond to a stimulus. Oscillations in the theta frequency (4-8Hz) during both cue presentation and stimulus presentation are implicated in proactive and reactive control processes. While reward has been shown to upregulate proactive control in adults, little work has assessed how reward influences theta oscillations during both proactive and reactive control throughout adolescence and pubertal development. Further, no work has sought to understand how EF abilities bolster reward-related changes in proactive or reactive control. Here, 68 adolescent males (Meanage=13.61, SDage=2.52) aged 9 – 17 years old completed a rewarded cued flanker paradigm while electroencephalogram (EEG) was collected. They also completed tasks from the NIH toolbox that tap the three EF domains. Behaviorally, reward hindered performance on proactive trials, particularly in mid-puberty, while enhancing performance on reactive trials. Reward was associated with increases in cue-locked theta power, but with overall reductions in cue-locked theta ICPS. Stim-locked theta power increased on reactive trials with increasing age, while stim-locked theta ICPS peaked in mid-adolescence for rewarded trials. Increased cue theta power was associated with worse performance on proactive trials. On proactive trials, adolescents with low levels of inhibitory control experience more reward-related interference, while reward-related interference was mitigated by better set-shifting abilities only in younger and older adolescents. In conclusion, reward differentially impacts proactive and reactive control throughout adolescent development and EF influences the impact of reward on proactive control throughout adolescence.Item THE ACOUSTIC QUALITIES THAT INFLUENCE AUDITORY OBJECT AND EVENT RECOGNITION(2019) Ogg, Mattson Wallace; Slevc, L. Robert; Neuroscience and Cognitive Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Throughout the course of a given day, human listeners encounter an immense variety of sounds in their environment. These are quickly transformed into mental representations of objects and events in the world, which guide more complex cognitive processes and behaviors. Through five experiments in this dissertation, I investigated the rapid formation of auditory object and event representations (i.e., shortly after sound onset) with a particular focus on understanding what acoustic information the auditory system uses to support this recognition process. The first three experiments analyzed behavioral (dissimilarity ratings in Experiment 1; duration-gated identification in Experiment 2) and neural (MEG decoding in Experiment 3) responses to a diverse array of natural sound recordings as a function of the acoustic qualities of the stimuli and their temporal development alongside participants’ concurrently developing responses. The findings from these studies highlight the importance of acoustic qualities related to noisiness, spectral envelope, spectrotemporal change over time, and change in fundamental frequency over time for sound recognition. Two additional studies further tested these results via syntheszied stimuli that explicitly manipulated these acoustic cues, interspersed among a new set of natural sounds. Findings from these acoustic manipulations as well as replications of my previous findings (with new stimuli and tasks) again revealed the importance of aperiodicity, spectral envelope, spectral variability and fundamental frequency in sound-category representations. Moreover, analyses of the synthesized stimuli suggested that aperiodicity is a particularly robust cue for some categories and that speech is difficult to characterize acoustically, at least based on this set of acoustic dimensions and synthesis approach. While the study of the perception of these acoustic cues has a long history, a fuller understanding of how these qualities contribute to natural auditory object recognition in humans has been difficult to glean. This is in part because behaviorally important categories of sound (studied together in this work) have previously been studied in isolation. By bringing these literatures together over these five experiments, this dissertation begins to outline a feature space that encapsulates many different behaviorally relevant sounds with dimensions related to aperiodicity, spectral envelope, spectral variability and fundamental frequency.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 Language Science Meets Cognitive Science: Categorization and Adaptation(2017) Heffner, Christopher Cullen; Newman, Rochelle S; Idsardi, William J; Neuroscience and Cognitive Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Questions of domain-generality—the extent to which multiple cognitive functions are represented and processed in the same manner—are common topics of discussion in cognitive science, particularly within the realm of language. In the present dissertation, I examine the domain-specificity of two processes in speech perception: category learning and rate adaptation. With regard to category learning, I probed the acquisition of categories of German fricatives by English and German native speakers, finding a bias in both groups towards quicker acquisition of non-disjunctive categories than their disjunctive counterparts. However, a study using an analogous continuum of non-speech sounds, in this case spectrally-rotated musical instrument sounds, did not show such a bias, suggesting that at least some attributes of the phonetic category learning process are unique to speech. For rate adaptation, meanwhile, I first report a study examining rate adaptation in Modern Standard Arabic (MSA), where consonant length is a contrastive part of the phonology; that is, where words can be distinguished from one another by the length of the consonants that make them up. I found that changing the rate of the beginning of a sentence can lead a consonant towards the end of the sentence to change in its perceived duration; a short consonant can sound like a long one, and a long consonant can sound like a short one. An analogous experiment examined rate adaptation in event segmentation, where adaptation-like effects had not previously been explored, using recordings of an actor interacting with a touchscreen. I found that the perception of actions can also be affected by the rate of previously-occurring actions. Listeners adapt to the rate at the beginning of a series of actions when deciding what they saw last in that series of actions. This suggests that rate adaptation follows similar lines across both domains. All told, this dissertation leads to a picture of domain-specificity in which both domain-general and domain-specific processes can operate, with domain-specific processes can help scaffold the use of domain-general processing.Item Action and perception: Neural indices of learning in infants(2016) Yoo Chon, Kathryn Hye Jin; Fox, Nathan A; Neuroscience and Cognitive Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Early human development offers a unique perspective in investigating the potential cognitive and social implications of action and perception. Specifically, during infancy, action production and action perception undergo foundational developments. One essential component to examine developments in action processing is the analysis of others’ actions as meaningful and goal-directed. Little research, however, has examined the underlying neural systems that may be associated with emerging action and perception abilities, and infants’ learning of goal-directed actions. The current study examines the mu rhythm—a brain oscillation found in the electroencephalogram (EEG)—that has been associated with action and perception. Specifically, the present work investigates whether the mu signal is related to 9-month-olds’ learning of a novel goal-directed means-end task. The findings of this study demonstrate a relation between variations in mu rhythm activity and infants’ ability to learn a novel goal-directed means-end action task (compared to a visual pattern learning task used as a comparison task). Additionally, we examined the relations between standardized assessments of early motor competence, infants’ ability to learn a novel goal-directed task, and mu rhythm activity. We found that: 1a) mu rhythm activity during observation of a grasp uniquely predicted infants’ learning on the cane training task, 1b) mu rhythm activity during observation and execution of a grasp did not uniquely predict infants’ learning on the visual pattern learning task (comparison learning task), 2) infants’ motor competence did not predict infants’ learning on the cane training task, 3) mu rhythm activity during observation and execution was not related to infants’ measure of motor competence, and 4) mu rhythm activity did not predict infants’ learning on the cane task above and beyond infants’ motor competence. The results from this study demonstrate that mu rhythm activity is a sensitive measure to detect individual differences in infants’ action and perception abilities, specifically their learning of a novel goal-directed action.Item LONGITUDINAL SINGLE-UNIT RECORDING IN THE MACAQUE FACE PATCH SYSTEM: IDENTITY AND PLASTICITY IN THE ANTERIOR FUNDUS FACE PATCH(2015) Jones, Adam Patrick; Leopold, David A; Butts, Daniel A; Neuroscience and Cognitive Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Face perception, a fundamental component of primate social behavior, is supported by a network of specialized visual regions within the ventral visual stream of humans and macaques. Discrete regions, or “patches” within this network respond preferentially to face images over non-face object images, with the majority of visually responsive neurons within these regions responding selectively to faces. In recent years, the functional specialization of neurons within particular fMRI-defined face patches has been studied intensively. In this series of studies, we have investigated one such patch (AF) located in the anterior fundus of the superior temporal sulcus using a new method longitudinal of electrophysiological single unit recording, where individual neurons can be isolated and monitored for several months using chronically implanted electrodes. We made use of this unique opportunity to study the responses of face-selective neurons in two different ways. Our first approach was the longitudinal observation of neurons over time scales relevant to behavioral learning. By observing single-units longitudinally, over several weeks of natural visual experience, as well as throughout the course of an intensive face-learning paradigm, we asked whether individual neurons would change their response selectivity. In the case of the learning paradigm, we asked whether there might be changes in face-selective neural responses that occur while the animal gradually acquired greater sensitivity for the distinctive features of novel face stimuli. For this, we taught the animal to recognize individual monkeys and humans using morphed faces of diminished identity levels. We found AF neurons were remarkably stationary in their responses over time scales of weeks and months, and even for periods as long as one year. Even during periods of intensive training using the stimuli for which the neurons appeared specialized, AF neurons demonstrate very limited change in their response patterns and selectivity. In our second approach- taking advantage of the fact that the neural response selectivity is unchanging across sessions- we accumulated neural responses to a large number of visual stimuli presented over multiple sessions, which allowed for both a broader sampling of the visual stimulus space and an enhanced sensitivity to the preferences of low-firing rate neurons. In this approach, we focused on visual responses to faces, asking how a conjunction of identity, species, viewing angle, and spatial scale shaped single-unit responses in face patch AF. Neurons in AF showed selective responses to each of these manipulations to different degrees. Within the domain of faces, most striking determinants of neural firing were face scale and the systematic, norm-based tuning for face identity. Many neurons were also strongly selective for macaque faces over human faces. Other factors, such as 3-dimensional face rotation, were less important. In addition to insight into the functional compartmentalization of the face-processing network, these results from face patch AF also provide a unique view into the relationship between high-level neural selectivity in the brain and the inherent trade-off between stability and plasticity that accompanies learning-induced changes in behavior.Item Interactions between appetitive and aversive processing in the human brain(2014) Choi, Jong Moon; Pessoa, Luiz; Neuroscience and Cognitive Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The brain mechanisms underlying anxiety/stress and motivation have been investigated extensively. However, they were mainly investigated independently of each other. Even though some studies discussed interactions between these two mechanisms, our understanding of the interaction between anxiety/stress and motivation is still limited. Motivation can be divided into two aspects. One is appetitive motivation to win appetitive outcome, and the other is aversive motivation for avoiding aversive outcome. Accordingly, in current functional MRI study, it was investigated how appetitive/aversive motivational processing would be influenced by anxiety/stress. In the first experiment I investigated interactions between threat and reward processing during anticipation of electric shock and monetary reward. Analysis of skin conductance data during a delay phase revealed competitive interaction between threat and reward processing. Analysis of imaging data during a delay phase also revealed the interaction effect in several regions, including midbrain/ventral tegmental area, caudate, putamen, bed nucleus of the stria terminalis, anterior insula, middle frontal gyrus, and dorsal anterior cingulate cortex. In the second experiment, the interaction between threat and reward/punishment processing was investigated. Analysis of imaging data during a delay phase revealed competitive interaction between threat and reward processing in left caudate. However, responses in the same site did show interaction between threat and punishment processing. Taken together, the findings in two studies suggest competitive processes of threat and reward, and independent processes of threat and punishment.