Biology Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/2749
Browse
12 results
Search Results
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 Effect of spatial working memory depletion on cerebral cortical dynamics of cognitive-motor performance(2020) Shaw, Emma Patricia; Gentili, Rodolphe J; Neuroscience and Cognitive Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Prior work has validated the use of resource depletion to directly probe the role of specific cognitive functions on human performance. Specifically, intensive recruitment of cognitive resources to successfully perform a task has been shown to result in performance decrements and decreased neural activation on subsequent tasks. Much of this work, however, was not conducted within the context of cognitive-motor performance and/or did not examine the underlying brain dynamics. Therefore, this study examined the effects of depleted spatial working memory (SWM) resources, critical for spatial information processing, on performance and brain dynamics (attentional reserve and cognitive-motor effort). Performance and electroencephalography were collected as thirty-five individuals, randomly assigned to an experimental or control group, with minimal prior videogame experience completed a cognitive-motor task at an easy and a hard level of difficulty before and after undergoing SWM resource depletion (experimental) or non-depletion (control). The SWM depletion protocol required intensive mental rotation, while the non-depletion protocol did not. Attentional reserve was assessed via the novelty-P3 component of the event-related potential and cognitive-motor effort was assessed via spectral power within the theta, low- and high-alpha frequency bandwidths. The results revealed both groups exhibited similar performance improvement on the cognitive-motor task post- compared to pre-SWM depletion/non-depletion. This was accompanied with a more efficient engagement of attentional resources (decreased novelty-P3) and a refinement of cortical activity (low-/high-alpha synchrony), which may reflect a practice effect. Furthermore, the control group exhibited theta synchrony under the hard compared to the easy level of challenge across all cortical regions regardless of when the cognitive-motor task was performed. This adaptive response, however, was absent within the frontal and temporal cortical regions (important for working memory, attentional control and visuospatial processes) for the experimental group post-SWM depletion. Additionally, the experimental group, post-relative to pre-SWM depletion, exhibited temporal theta desynchrony and synchrony during the hard and easy level of challenge, respectively. These findings collectively suggest intensive cognitive task performance has a combined neurocognitive benefit (i.e., practice effect) and cost (i.e., lack of adaptive response due to depleted resources) during subsequent cognitive-motor performance requiring similar cognitive processes as that of the depleting task.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 INFLUENCE OF MOTIVATION ON EMOTION REGULATION AND MOTOR PERFORMANCE: EXAMINATION OF A NEURO-AFFECTIVE MODEL(2016) Tan, Ying; Hatfield, Bradley D; Neuroscience and Cognitive Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Mental stress is known to disrupt the execution of motor performance and can lead to decrements in the quality of performance, however, individuals have shown significant differences regarding how fast and well they can perform a skilled task according to how well they can manage stress and emotion. The purpose of this study was to advance our understanding of how the brain modulates emotional reactivity under different motivational states to achieve differential performance in a target shooting task that requires precision visuomotor coordination. In order to study the interactions in emotion regulatory brain areas (i.e. the ventral striatum, amygdala, prefrontal cortex) and the autonomic nervous system, reward and punishment interventions were employed and the resulting behavioral and physiological responses contrasted to observe the changes in shooting performance (i.e. shooting accuracy and stability of aim) and neuro-cognitive processes (i.e. cognitive load and reserve) during the shooting task. Thirty-five participants, aged 18 to 38 years, from the Reserve Officers’ Training Corp (ROTC) at the University of Maryland were recruited to take 30 shots at a bullseye target in three different experimental conditions. In the reward condition, $1 was added to their total balance for every 10-point shot. In the punishment condition, $1 was deducted from their total balance if they did not hit the 10-point area. In the neutral condition, no money was added or deducted from their total balance. When in the reward condition, which was reportedly most enjoyable and least stressful of the conditions, heart rate variability was found to be positively related to shooting scores, inversely related to variability in shooting performance and positively related to alpha power (i.e. less activation) in the left temporal region. In the punishment (and most stressful) condition, an increase in sympathetic response (i.e. increased LF/HF ratio) was positively related to jerking movements as well as variability of placement (on the target) in the shots taken. This, coupled with error monitoring activity in the anterior cingulate cortex, suggests evaluation of self-efficacy might be driving arousal regulation, thus affecting shooting performance. Better performers showed variable, increasing high-alpha power in the temporal region during the aiming period towards taking the shot which could indicate an adaptive strategy of engagement. They also showed lower coherence during hit shots than missed shots which was coupled with reduced jerking movements and better precision and accuracy. Frontal asymmetry measures revealed possible influence of the prefrontal lobe in driving this effect in reward and neutral conditions. The possible interactions, reasons behind these findings and implications are discussed.Item The Impact of Motor Learning on Motor Behavior and Cortical Dynamics in a Complex Stressful Social Environment(2016) Saffer, Mark Ian; Hatfield, Bradley; Neuroscience and Cognitive Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)An economy of effort is a core characteristic of highly skilled motor performance often described as being effortless or automatic. Electroencephalographic (EEG) evaluation of cortical activity in elite performers has consistently revealed a reduction in extraneous associative cortical activity and an enhancement of task-relevant cortical processes. However, this has only been demonstrated under what are essentially practice-like conditions. Recently it has been shown that cerebral cortical activity becomes less efficient when performance occurs in a stressful, complex social environment. This dissertation examines the impact of motor skill training or practice on the EEG cortical dynamics that underlie performance in a stressful, complex social environment. Sixteen ROTC cadets participated in head-to-head pistol shooting competitions before and after completing nine sessions of skill training over three weeks. Spectral power increased in the theta frequency band and decreased in the low alpha frequency band after skill training. EEG Coherence increased in the left frontal region and decreased in the left temporal region after the practice intervention. These suggest a refinement of cerebral cortical dynamics with a reduction of task extraneous processing in the left frontal region and an enhancement of task related processing in the left temporal region consistent with the skill level reached by participants. Partitioning performance into ‘best’ and ‘worst’ based on shot score revealed that deliberate practice appears to optimize cerebral cortical activity of ‘best’ performances which are accompanied by a reduction in task-specific processes reflected by increased high-alpha power, while ‘worst’ performances are characterized by an inappropriate reduction in task-specific processing resulting in a loss of focus reflected by higher high-alpha power after training when compared to ‘best’ performances. Together, these studies demonstrate the power of experience afforded by practice, as a controllable factor, to promote resilience of cerebral cortical efficiency in complex environments.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 EFFECTS OF AGING ON MIDBRAIN AND CORTICAL SPEECH-IN-NOISE PROCESSING(2016) Presacco, Alessandro; Andreson, Samira; Simon, Jonathan Z.; Neuroscience and Cognitive Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Older adults frequently report that they can hear what they have been told but cannot understand the meaning. This is particularly true in noisy conditions, where the additional challenge of suppressing irrelevant noise (i.e. a competing talker) adds another layer of difficulty to their speech understanding. Hearing aids improve speech perception in quiet, but their success in noisy environments has been modest, suggesting that peripheral hearing loss may not be the only factor in the older adult’s perceptual difficulties. Recent animal studies have shown that auditory synapses and cells undergo significant age-related changes that could impact the integrity of temporal processing in the central auditory system. Psychoacoustic studies carried out in humans have also shown that hearing loss can explain the decline in older adults’ performance in quiet compared to younger adults, but these psychoacoustic measurements are not accurate in describing auditory deficits in noisy conditions. These results would suggest that temporal auditory processing deficits could play an important role in explaining the reduced ability of older adults to process speech in noisy environments. The goals of this dissertation were to understand how age affects neural auditory mechanisms and at which level in the auditory system these changes are particularly relevant for explaining speech-in-noise problems. Specifically, we used non-invasive neuroimaging techniques to tap into the midbrain and the cortex in order to analyze how auditory stimuli are processed in younger (our standard) and older adults. We will also attempt to investigate a possible interaction between processing carried out in the midbrain and cortex.Item Electroencephalography (EEG) and measures of nociception in cattle(2013) Drnec, Kim Ann; Stricklin, William R; Simon, Jonathan Z; Neuroscience and Cognitive Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The first known bovine laser evoked potential (LEP), an EEG response to noxious laser heat stimuli, was measured in 2-3 year old Holstein cows (n=5). The amplitude of the bovine LEP correlated significantly (P<. 05) with behavior scores, the surrogate for self-reporting in human studies. Importantly, and comparable to human studies, the LEP occurs at a latency within which it is considered that cortical potentials reflect increasingly complex cognitive processes, rather than those that are reflexive and non-conscious. Differences between the bovine and human LEP were also determined, that cannot be fully explained at this time. The lack of standardization for large animal EEG-investigations is problematic regarding data sharing across labs. A proposed standard method, for collecting and processing EEG in cattle was developed and is presented. Compared to human studies, signal processing of bovine data required significantly more stringent rejection criteria for data analysis. For example, while wavelet denoising is often used in human EEG; it was found essential for extracting a bovine LEP. In addition, explicitly addressing whether of not cortical potentials were being recorded was necessary to provide foundational background knowledge of bovine EEG. To this end, EEG was recorded under conditions designed to simulate the suppression and excitation of the primary visual cortex, as is measured in humans using eyes-open and eyes-closed. The simulation contrasted a dark and light environment. I propose this protocol to be used in the future large animal studies to verify that cortical potentials are being measured before EEG data recording. My results demonstrate that bovine EEG is a useful bovine cognitive science method, but more sophisticated signal processing techniques are needed to ameliorate issues of artifact. Lowered signal to noise ratios is considerably problematic for evoked response studies in large animals. Importantly, this research determined that a bovine LEP is measurable, and by analogy to human perceptual studies, I contend this demonstrates the cow experiences both the sensation and perception of noxious stimulus as painful.Item A PROGRAMMATIC RESEARCH APPROACH TO UNDERSTANDING THE IMPACT OF TEAM ENVIRONMENT ON CEREBRAL CORTICAL DYNAMICS AND ATTENTION(2012) Miller, Matthew Walker; Hatfield, Bradley D; Neuroscience and Cognitive Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation describes a programmatic research approach to understanding how team environments alter individuals' brain dynamics so as to produce variations in individuals' cognitive-motor performances. This research is of fundamental interest as humans frequently perform in team environments. Specifically, the central purpose of this research was to determine if adaptive team environments are conducive to efficient brain dynamics such that tasks are accomplished with minimal neural costs. The dissertation is comprised of four studies (papers), each of which makes a unique contribution to the dissertation's central objective. The first paper reports a positive directional relationship between cerebral cortical activation as well as networking and task load. The second paper describes a new neurophysiological method for indexing attentional reserve, which is positively related to the efficiency of cerebral cortical activation and networking. The third paper describes the development of a paradigm employed to investigate the impact of team environment on neurocognitive functioning. This study used non-physiological techniques to index neurocognitive functioning while participants performed a cognitive-motor task in various team environments. Results suggest that, relative to neutral environments, maintaining performance in maladaptive team environments comes at a neurocognitive cost, while adaptive team environments enhance performance without such a cost. The final study applied the neurophysiological methods described in the first two studies to the team environment paradigm employed in the third study to provide neurobiological evidence in support of the conclusions reached in the third paper. Additionally, the final paper provides insight into the neurobiological changes underlying the alterations in neurocognitive functioning and task performance reported in the third paper. Specifically, the final paper reports that, relative to neutral environments, maintaining performance in maladaptive team environments comes at the expense of the efficiency of cerebral cortical activation and attentional reserve, while adaptive team environments enhance performance without such costs. Additionally, the final paper suggests that adaptive team environments may generate more optimal states of arousal, leading to performance enhancement. By comprehending the impact of team environments on brain dynamics, humans performing as members of teams in a variety of settings may be better equipped to maximize their performances.Item Brain function underlying adaptive sensorimotor control in children with and without Developmental Coordination Disorder(2012) Pangelinan, Melissa Marie; Clark, Jane E; Neuroscience and Cognitive Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)One child in every classroom (6% of children) suffers from Developmental Coordination Disorder (DCD). Children with DCD exhibit marked impairments in movement planning and adaptive visuomotor behavior. However, few studies have investigated the brain functions that underlie behavioral difficulties exhibited by children with DCD. The overarching objective of this dissertation was to examine brain function using electroencephalography (EEG) both at rest and during the performance of visuomotor tasks of different levels of complexity (i.e. static vs. dynamic task environments) to determine if deficits in motor behavior are related to disrupted brain function in children with DCD. The first study revealed that the cortical activation patterns exhibited by children with DCD at rest were different than their typically developing (TD) peers, particularly for the left motor cortical region. Moreover, the activation patterns of children with DCD were similar to the patterns previously reported for young TD children, suggesting a "maturational lag" in brain activation specific to motor function. For the remaining studies, children performed line drawing movements on a computer tablet towards visual targets presented on a computer screen. These studies examined whether or not children with DCD exhibit different cortical activation patterns during the execution of goal-directed drawing movements. In Study 2, children performed simple drawing movements to stationary targets. The performance of children with DCD followed the same age-related developmental trajectory as TD children. However, children with DCD engaged motor planning and control brain areas to a greater extent throughout the movement compared to TD children, suggesting greater cortical effort to complete the task. For the last two studies, children performed drawing movements in dynamic environments in which visual stimuli cued participants to either abruptly stop ongoing movements (Study 3.1) or to modify movements online to displaced target locations (Study 3.2). Results from Study 3.1 demonstrated that children with DCD do not have difficulties inhibiting movements, a finding that may be attributed to similar cortical activation patterns as the TD children in response to stop signals. Study 3.2 revealed that children with DCD exhibit difficulties modifying movements online, which may be due to a lack of preparatory cortical activation in this group. Taken together, this dissertation provides evidence that disrupted cortical function both at rest and during movement planning may underlie differences in motor performance in DCD.