Dual-task studies have shown higher sensitivity for stimuli presented at the targets of upcoming actions. Generally, movement outcome feedback is also obtained at action targets. This thesis examined whether attention is directed to action targets for the purpose of action selection, as previously concluded, or if attention is directed to monitor feedback about movement outcomes as supported by skilled-action research. Across seven experiments, participants executed either a pointing movement (Experiments 1 – 5) or a saccade (Experiments 6 and 7), while simultaneously identifying a discrimination target ('E' or '3') among distractors (2s and 5s). Action targets were generally cued by a central arrow. Discrimination target identification accuracy measured attention allocation. Crucially, movement accuracy feedback was presented at a spatially separate location from the action target. It was found that during the planning of goal-directed actions, attention is allocated to monitor movement outcomes, even if this information is provided at a spatially separate location from the action target. Attending the separate feedback location resulted in slower reaction times and less accurate pointing. Clear and consistent perceptual enhancement was also demonstrated at the action target location, even when no intrinsic or extrinsic feedback about the action could have been gained from attending there. Specific to saccades, it was found that attention is allocated before saccade execution to both the saccade goal and to the predicted future retinal location of feedback information. Lastly, perceptual performance is greater in general when participants perform the dual-task visually open-loop, that is without visual feedback from the moving hand. These results are novel in showing that attention appears to be required for action target selection, independently of the need to monitor expected locations of feedback.

In the influential perception-action model, the ventral visual system of the primate brain serves to obtain knowledge of objects in the environment, while the dorsal system serves to control actions in interaction with those objects. In recent years, criticism of the model has gained momentum following reports of evidence that involvement of the two systems may not principally depend on whether observers are engaged in action or perception tasks. This thesis appraises the perception-action model over the course of five experiments that test a number of the model’s central assertions. Evidence for an alternative functional characterization of the dorsal and ventral systems is obtained. Specifically, the evidence suggests that the dorsal system can be involved in both action and perception on the basis of fast egocentric information pickup, while the ventral system can be involved in both perception and action on the basis of slower allocentric information pickup. This raises the possibility that a more fundamental distinction pertains to the characteristics of information pickup by the two systems rather than to the behavioral functions subserved. The thesis develops a stance in which involvement of the two systems in the visual guidance of behavior is dependent on their operational characteristics in combination with the constraints of the task. The proposed relevant task constraints are: (i) whether tasks allow for egocentric and/or allocentric information pickup, (ii) the amount of time that is available for information pickup in a task and, possibly, (iii) whether stimuli are located within or outside functional space (the space that affords action for an observer). Whether a task requires an immediate or a delayed response is of less importance. It is argued that while the typical requirements of perception and action tasks bring about a tight coupling between perception and the ventral system and action and the dorsal system, this coupling is not invariant; perception can involve fast egocentric information pickup and action can involve slower allocentric information pickup. The findings are discussed in the context of higher-level theories of visual perception. It is proposed that the view of the dorsal and ventral visual systems that is suggested by the findings presented in this thesis corresponds better with ecological than with constructivist approaches to visual perception. / published_or_final_version / Human Performance / Doctoral / Doctor of Philosophy

Thesis (Ph. D.)--University of California, San Diego, 1981. / Vita. Includes bibliographical references (leaves 127-130).

Thesis (Ph. D.)--University of California, San Diego, 1981. / Vita. Includes bibliographical references (leaves 127-130).

The relationship between perinatal complications and sensory-motor functions was examined. Information from the Maternal Perinatal Scale (MPS) was used to predict factor scores of the Dean Sensory-Motor Battery (DSMB). Participants were 187 normal nonreferred children who were administered the DSMB while their mothers completed the MPS. Using MPS items as predictors, separate stepwise regression analyses for each DSMB factor found that 11 - 16% of variance could be accounted for in sensory-motor performance. At least three MPS items significantly contributed to the prediction of each DSMB factor. Predictors of Sensory and Simple Motor functions (DSMB Factor I) included maternal bleeding during pregnancy, delay between membrane rupture (water break) and onset of labor, and evidence of hypoxia. Evidence of hypoxia, maternal bleeding during pregnancy, and delay between water break and labor onset were predictive of Motor and Complex Sensory functions (DSMB Factor II). In addition, gender of the child joined maternal bleeding during pregnancy, amount of swelling during pregnancy, and mother's height in predicting Subcortical Motor functions (DSMB Factor III). Additional analyses using a canonical correlation confirmed the results of the regression analyses. A linear composite of sensory and motor variables was primarily defined by DSMB factors I and II. The linear composite of perinatal information was defined primarily by the same items that emerged as significant predictors of sensorymotor functions in the regression analyses. Most notably, a redundancy analysis indicated that about 20% of variance in DSMB factor scores could be accounted for by a linear composite of perinatal information. In general, sensory-motor performance decreased as severity of perinatal complications increased. Results were discussed in terms of the implications of using a normal non-referred population. More importantly, the present data suggested the possibility that 1) the relationship between perinatal complications and sensory-motor functions may exist on a continuum rather than the dichotomous diagnosis/no diagnosis, and 2) the synergistic influence of multiple perinatal complications may contribute to the manifestation of clinically significant behaviors. The role of sensory-motor functions as a foundation for more complex behaviors is also discussed. / Department of Educational Psychology

Thesis (Ph. D.)--University of Wisconsin--Madison, 1975. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 184-201).

The neurophysiological signals that are recorded in EEG (electroencephalography) and MEG (magnetoencephalography) originate from current flow perpendicular to the cortical surface due to the columnar organization of pyramidal cells in the cortical gray matter. These locations and directions have been used as anatomical constraints for dipolar sources in estimations of neural activity from MEG recordings. Here we extend anatomically constrained beamforming to EEG, which requires a more sophisticated forward model than MEG due to the blurring of the electric potential at tissue boundaries, but in contrast to MEG, EEG can account for both tangential and radial sources. Using computed tomography (CT) scans we create a realistic three-layer head model consisting of tessellated surfaces representing the tissue boundaries cerebrospinal fluid-skull, skull-scalp and scalp-air. The cortical gray matter surface, the anatomical constraint for the source dipoles, is extracted from magnetic resonance imaging (MRI) scans. EEG beamforming is implemented in a set of simulated data and compared for three different head models: single sphere, multi-shell sphere and realistic geometry multi-shell model that employs a boundary element method. Beamformer performance is also analyzed and evaluated for multiple dipoles and extended sources (patches). We show that using anatomical constraints with the beamforming algorithm greatly reduces computation time while increasing the spatial accuracy of the reconstructed sources of neural activity. Using the spatial Laplacian instead of the electric potential in combination with beamforming further improves the spatial resolution and allows for the detection of highly correlated sources. / by Vyacheslav Murzin. / Thesis (Ph.D.)--Florida Atlantic University, 2010. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2010. Mode of access: World Wide Web.

Examination of how the brain mediates emotional experience is now an area of significant and intense research interest. This is an important endeavour considering that emotion is a key component in vulnerability factors governing risk for mood and anxiety disorders. Recent neuropsychological and neuroimaging studies are also beginning to explore the effects of antidepressants on the processing of emotional stimuli in healthy participants to help understand the role of neurochemicals in affective behaviour more broadly. Unfortunately the literature is fraught with contradictions and complications resulting from the technique used, task instructions, selection of stimuli and gender differences. The aim of the current thesis therefore, was to investigate emotional processing in healthy participants and to examine the impact of serotonergic augmentation on this processing through the presentation of visual emotional stimuli and examination of self report, peripheral- and neurophysiological measures of emotional responsiveness. Seventy five images low in arousal content, selected from the International Affective Picture System (IAPS) and categorised as pleasant, neutral and unpleasant, were presented to participants in four experimental studies. Findings support previous literature suggesting that there is substantial overlap in frontal neural circuitry when the brain processes emotional images of different valence. Gender differences in the processing of visual emotional stimuli were also observed however suggesting the need for future studies to take such factors into account. In particular, females unlike males displayed right-sided, frontal, neurophysiological activations in response to unpleasant relative to neutral images. Emotional valence was also found to modulate heart rate (HR) thereby confirming the reliability and validity of the task-viewing paradigm. Augmentation of serotonin was found to suppress any differences in HR across the three differently valenced categories of images, while neurophysiological responses were potentiated during pleasant valence but suppressed during unpleasant valence. In summary, the studies included in this thesis provide evidence for neurophysiological modulation by emotional content and gender. In addition, the studies employ a more systems-based approach to the study of antidepressant action, through examination of the neurophysiological responses to visual emotional stimuli. This approach may lead to greater understanding of the functional consequences of neurochemical modulation on cortical networks involved in emotional processing.

Thesis (Ph.D.)--York University, 2004. Graduate Programme in Biology. / Typescript. Includes bibliographical references (leaves 292-305). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://wwwlib.umi.com/cr/yorku/fullcit?pNQ99265

published_or_final_version / Sports Science / Master / Master of Science in Sports Science