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

The primary intent of this study was to explore fundamental questions about the role and relationship between motor (MI) and visual (VI) imagery within the context of estimating reach. Experiment 1 examined and compared VI and MI tasks under matched environmental conditions with the intent to explore the distinction and cooperation of the visual and motor systems in representing actions. The design of this experiment included an interference paradigm modified from Stevens (2005) in which six blocks of trials (conditions) were used: MI, VI, MI with visual interference, MI with motor interference, VI with motor interference, and VI with visual interference. Results indicated that MI was significantly more accurate than VI in regard to total error, distribution of error and mean bias (p <= .05). Significant increases in the number of errors and estimation bias were found when the modalities for the imagined task and the interference task were matched. The data showed that motor tasks interfered with the ability to MI, whereas visual tasks interfered with the ability to VI. Experiment 2 included a response-delay paradigm modified from Bradshaw and Watt (2002) in which eight blocks of trials were used: MI and VI conditions with no-delay and delays of 1-, 2- and 4 s. Overall, this experiment demonstrated that response-delay influenced accuracy of the MI (visuomotor) task, but not the VI (perceptual) task. That is, after a 4s delay, error in MI increased significantly. Interestingly, these results may indicate a crucial temporal constraint for the representation of distance, isolated in the visuomotor system. In view of both experiments, the findings are consistent with the notion of a distinction between vision for perception (VI) and vision for action (MI) as advanced by Goodale, Westwood & Milner (2004). In conclusion, VI seems to delineate relevant spatial parameters within the environment and then transfer the information to MI. At this point, information is computed in terms of biomechanical possibilities for a certain movement. In summary, just as perception and action are firmly linked, so too are MI and VI.

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Autism spectrum disorders (ASDs) affect 1 in every 88 U.S. children. ASDs have been described as neurological and developmental disorders impacting visual, motor, and visual-motor integration (VMI) abilities that affect academic achievement (CDC, 2010). Forty-five participants (22 ASD and 23 Typically Developing [TD]) 8 to 14 years old completed the Bender-Gestalt Test, Second Edition (BG II), Beery-Buktenica Developmental Test of Visual-Motor Integration, 5th Edition (VMI-V), NEPSY Second Edition (NEPSY-II), Test of Visual Perceptual Skills-3 (TVPS-3), Navon Task, Kaufman Test of Educational Achievement, Second Edition, Kaufman Brief Intelligence Test, Second Edition, Behavior Assessment Scale for Children, Second Edition, and Autism Spectrum Screening Questionnaire. Three hypotheses examined whether students with ASDs were more likely than TD peers to have: (1) a visual processing bias; (2) fine motor difficulties; and (3) VMI difficulties. Additional hypotheses analyzed the relationship between (4) local processing bias and fine motor difficulties on VMI ability and (5) local processing bias, fine motor difficulties, and VMI difficulties on academic achievement. A series oft-tests indicated the TVPS-3 (p=.72), Navon Task (p= .78), BG-II (p = .39), and VMI-V (p = .14) were not significantly different between groups. Students with ASDs demonstrated increased difficulty compared to TD students on the NEPSY-II (p = .01) and slower completion time on the Navon Task (p = .01). Regression analyses for VMI indicated the best predictors for the BG-II (p < .001) were the TVPS-3 and Navon Completion Time; the best predictor for the VMI-V (p< .001) was the TVPS-3. Regression analyses indicated that VMI-V predicted all domains of academic achievement. In addition to VMI-V, fine motor skills related to writing achievement, and BG-II related to math achievement. Based on the results, the speed of processing plays an important role on VMI skills and academic achievement, more so than the local processing bias. Although this study may have been impacted by homogeneity in the participants, it investigates a relationship between visual processing biases, fine motor difficulties, visual-motor integration and academic achievement that has received little attention in the literature. Findings can inform the development of more effective interventions for academic functioning for students with ASDs.

The spatiotemporal dynamics of ongoing beta band (15-30 Hz) cortical oscillations and the modulation of this neural activity by tactile input and movement provide insight into how the brain achieves proper sensorimotor processing. Earlier studies have shown that the synchrony of the cortical beta rhythms within and between central and peripheral neuronal populations is modulated during and following somatosensation or movement, and correlated with effective motor control. In addition, abnormal levels of beta oscillations in the basal ganglia are correlated with motor dysfunction in Parkinson’s disease. Numerous functional roles for the beta rhythm have been proposed – ranging from inhibition to the facilitation of long-range communication. However, the neural network that generates the sensorimotor beta rhythm and the functional significance of this activity have not been fully specified. Thus, I used magnetoencephalography to complete three studies of the beta rhythm in healthy right-handed adults. In the first study, I hypothesized that finger vibration at beta frequencies would generate stimulus-coherent neuronal firing in the neural network that generates the beta rhythm – thus revealing the nodes of this network. Data were analyzed for nineteen subjects (10 females). The coherent activity was revealed using a novel analysis technique that generated whole-brain maps of inter-trial synchrony during passive repetitive finger vibration at 23 Hz. These maps identified contralateral primary somatosensory cortex (SI), posterior parietal cortex, supplementary motor area and primary motor cortex (MI), and ipsilateral brainstem as nodes in the network. In the second study, I correlated changes in focused attention with modulations in beta band cortical responses to specify the functional significance of this activity. Data were analyzed for twelve subjects (7 females). With increased focused attention to the stimulus, I hypothesized that the beta band responses to finger vibration would be enhanced in areas involved in somatosensory processing. A transient increase in the magnitude of beta oscillations in MI (event-related synchronization) following vibration offset was significantly enhanced by attention, as compared to passive stimulation. In addition, attention caused the suppression of beta oscillations (event-related desynchronization, ERD) in ipsilateral SI beginning 1 second prior to vibration offset. Strong attention-modulation of the beta rhythm outside of contralateral SI implies that these changes are indicative of higher-order processing of afferent information. In the third study, I tested the hypothesis that synchrony between beta rhythms in contralateral MI and the relevant muscle supports effective neuronal communication. I correlated changes in task performance with corticomuscular coherence (CMC) during the sustained application of force to match a visually-presented target. Data were analyzed for eighteen subjects (9 females). As predicted, CMC in MI was significantly increased during improved performance in this task. This suggests that central-peripheral synchrony plays an important functional role in sustaining isometric muscle control. Concurrent beta ERD in bilateral SI and primary visual cortices during the contraction indicates the importance of afferent feedback in this task. Gender-related effects were not investigated in these studies. Beta band neuromagnetic responses to movement and somatosensation identify a pervasive neural network that is involved in processing the relevant properties of somatic input and regulating sustained motor output.

This dissertation is comprised of three studies investigating the hypothesis that people who stutter (PWS) differ from people who do not stutter (PNS) in their motor skill learning abilities. The first study in this dissertation examined the ability to learn a novel sequential speech task following a 24-h retention period. Despite slower sequence durations compared to the PNS, PWS showed the ability to retain what they had learned for all measured variables on day one and following a 24-h consolidation period. The second study in this dissertation examined the ability to learn a sequential finger tapping task by observing the ability to produce the sequence under both tests of retention and interference. For tests of retention, PWS showed the ability to retain improvements in performance for all measured variables, albeit at slower speeds compared to PNS. For tests of interference, a significant interaction for reaction time and sequence duration revealed that PNS’ performance reached a relative plateau while PWS’ performance continued to show improvement. The third study in this dissertation investigated the extent to which individual differences in motor learning are associated with differences in stuttering treatment outcome. PWS participating in an intensive fluency treatment program were assessed for their working memory ability and their motor iii learning performance on a syllable reading and finger tapping task. Treatment success was measured at pre-treatment, post-treatment and six months follow-up using percent syllables stuttered, introspective clinical characteristics (OASES; Yaruss, 2010) and fluency effort. The relationship between motor learning and treatment outcome was examined using multiple regression analyses. Results did not support the hypothesis that the ability to learn a simple speech and nonspeech motor task is predictive of treatment outcome. Although treatment proved successful as evidenced by percent syllables stuttered and OASES scores, scores of fluency effort indicated that participants had not automated their newly learned fluency skills when speaking in everyday conversations. Together, these studies do not support the hypothesis of a motor learning deficit in PWS but rather support the assumption of limited motor abilities. Limited motor abilities are discussed as having implications to stuttering treatment outcome.

Simulation has not been extensively studied for teaching rehabilitation practitioners technical skills. The purpose of this study is to test the efficacy of an artificial hand as a teaching tool for orthosis-making. Thirty-four participants were randomized into three groups. The first group made five orthoses on a human hand, the second made five orthoses on a model hand, and the third made one orthosis on a human hand. A one-week transfer test consisted of all participants making one orthosis on a human hand. Their performance and orthoses were evaluated using a validated checklist and global rating scale. No differences were found between groups for process-related measures. The model hand group did better on final product measures and had a larger movement time than the other two groups. Practicing on artificial hands is a useful way of learning to make orthoses. Additionally, higher practice volume did not lead to better performance.

Vision is important for the control of upper limb movements (Woodworth, 1899). How and when vision is used during a limb movement continues to be debated. In this thesis, I examined the use of visual feedback as a function of retinal limb position. Individuals made rapid upper limb aiming movements to a target location and vision was provided when the limb was at varying degrees of retinal eccentricity. The temporal characteristics, endpoint accuracy and precision, as well as the spatial variability of the limb trajectories were recorded and analyzed. No relationship was observed between retinal limb positions and the use of visual feedback during the movements. These results suggest that the use of vision during limb movements is not directly tied to the neuroanatomy of the eye and challenges continuous models of upper limb control.

Vision is important for the control of upper limb movements (Woodworth, 1899). How and when vision is used during a limb movement continues to be debated. In this thesis, I examined the use of visual feedback as a function of retinal limb position. Individuals made rapid upper limb aiming movements to a target location and vision was provided when the limb was at varying degrees of retinal eccentricity. The temporal characteristics, endpoint accuracy and precision, as well as the spatial variability of the limb trajectories were recorded and analyzed. No relationship was observed between retinal limb positions and the use of visual feedback during the movements. These results suggest that the use of vision during limb movements is not directly tied to the neuroanatomy of the eye and challenges continuous models of upper limb control.

It is widely thought that emotional stimuli receive privileged neural status compared to their non-affective counterparts. This prioritization, however, comes at a cost, as the neural capacity of the human brain is finite; the prioritization of any one object comes at the expense of other concurrent objects in the visual array competing for awareness (Desimone & Duncan, 1995). Despite this reality, little work has examined the functional benefit derived from the perceptual prioritization of affective information. Why do we preferentially attend to emotional faces? According to evolutionary accounts, emotions originated as adaptations towards action, helping to prepare the organism for movement (Darwin, 1872; Frijda, 1986). The current dissertation examines this from the perceptive of visual neuroscience and motor cognition. Chapters 1 and 2 examine the mechanisms involved during the perceptual prioritization of emotional content in the context of action system modulation. Chapters 3 and 4 then directly examine emotions effect on oculomotor action output. Results across the studies are discussed in the context of evolutionary theories related to biological origins of emotional expression.