UMD Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/3
New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a given thesis/dissertation in DRUM.
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Item Psychophysiological investigation of attentional processes during motor learning(2011) Rietschel, Jeremy Carl; Hatfield, Bradley D; Neuroscience and Cognitive Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)As one becomes more proficient at a motor task the attentional demand required to perform that task decreases. Behavioral evidence suggests that experienced individuals possess greater attentional reserve during task execution compared to novices, such that, they are better able to cope with additional, possibly unexpected, challenges. This advantage may be the result of streamlining the neural processes underlying motor planning and execution over the course of learning. Such psychomotor efficiency reduces the demand on cortical resources imposed by the primary task such that they are available for coping with challenge beyond that of the task. However, this hypothesis has not been tested. The aim of this study was to provide neurobiological evidence of the positive relationship between motor skill and attentional reserve. Twenty-one participants were randomly assigned to one of two groups, a group that learned a novel visuomotor distortion task, and a control group that performed the same task with no distortion (i.e., no learning). For the duration of the task, event-related brain potentials (ERPs) elicited by a set of novel stimuli were recorded. The dynamic modulation of ERP component amplitude was used as an index of attentional reserve. We predicted that component amplitudes would initially be diminished in the learning group relative to the control group, but that there would be a progressive increase in amplitude as a function of learning; by contrast, we predicted that ERP component amplitudes would remain relatively stable in the control group. Importantly, task performance, as measured by initial directional error, was initially worse in the learning group relative to control group and significantly improved over the course of exposure, whereas the control group's performance was stable. This suggests the visuomotor distortion task employed was successful in serving as a model of motor skill acquisition. Analyses of the ERPs elicited by the auditory probes revealed that the exogenous components, N1 and P2, were not different between the two groups and did not change over the course of learning suggesting that early sensory processing was comparable between the two groups. Notably, the novelty P3 component-an index of the involuntary orienting of attention--was initially attenuated in the learning group relative to the control group, but progressively increased in amplitude as a function of learning in the learning group only. This suggests that attentional reserve increased as a function of motor skill acquisition, such that greater attentional resources were available to process the auditory probes. The current study provides psychophysiological evidence that attentional reserve increases as a function of motor skill acquisition. Moreover, the metric developed for this study provides a means to assess cognitive/motor learning in both applied cognitive and clinical domains.Item Arousal and skilled motor performance: The mediating role of cerebral cortical dynamics(2006-08-16) Rietschel, Jeremy Carl; Hatfield, Bradley D; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Despite achievement of a highly skilled level of motor competence, elucidation of the multiple factors contributing to variability of motor performance remains somewhat enigmatic. The inverted-U hypothesis posits moderate levels of arousal as essential to optimal performance; this suggests that arousal may be a key player of this variability. The purpose of this study was to examine the psychophysiological concomitants of moderate as compared to low arousal. Specifically we hypothesized a decrease in coherence between the temporal lobes (T3-verbal-analytical processing & T4-visuo-spatial processing) and the motor planning region (Fz), accompanied by an increase in task performance. Fifteen college undergraduates (9 females, 6 males, mean age = 23.4, SD = 4.22) participated in two days of testing. Day one consisted of 340 trials of a novel visuomotor pointing task to achieve task competency. On the second day, EEG data were recorded during both a Performance Alone (PA) condition vs. a Social-Evaluation and Competition (SE&C) condition, which were counterbalanced. Coherence estimates were subjected to a 2 x 2 ANOVA comparing Condition x Hemisphere; post hoc testing was completed using paired-t tests. The arousal-manipulation check of the two experimental protocols (PA vs. SE&C) provided by the autonomic measures and self-reports indicated an increase from a low to moderate level of arousal during the SE&C condition. There was a statistical interaction between condition and hemisphere revealing reduced coherence during SE&C only between T4-Fz (t(14) = 3.084, p = 0.008). Additionally, there was a increase in motor performance (t(13) = 2.171, p = 0.049). Consistent with the inverted-U hypothesis and our predictions as stated for moderate arousal relative to performing alone, there was a subsequent increase in performance coupled with a decrease in coherence between the visuo-spatial and the motor-planning regions. In light of the significantly improved kinematics, the reduction in networking between these task relevant areas is seen as an adaptive refinement of cortico-cortical communication as one moves from low towards optimal arousal.