The majority of corticospinal projections in primates and all corticospinal projections in other mammals exert their influence by integrating into spinal interneuronal circuits. Interneurons therefore represent an evolutionarily conserved target through which the corticospinal tract achieves motor and sensory control. Here I describe the postnatal maturation of the corticospinal tract. I show work aimed at fractionating cortical projections by combining recently developed retrograde viral tracing strategies with genetic access to distinct spinal interneuron populations. Using a 3-D reconstruction pipeline, I discuss the cortical origins of the corticospinal pathway in mice. I then demonstrate the differential distribution of corticospinal inputs to three interneuron populations with divergent functional roles. These studies suggest that primary motor cortex contacts functionally diverse spinal interneurons whilst premotor and somatosensory cortical regions are more restricted in their postsynaptic targeting.

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Thesis (Ph.D.)--Auburn University, 2007. / Abstract. Includes bibliographic references (ℓ. 84-92)

Thesis (M. Sc.)--University of Canterbury, 2007. / Typescript (photocopy). Includes bibliographical references (leaves 74-77). Also available via the World Wide Web.

Thesis (Ph. D.)--University of Chicago, Committee on Neurobiology, August 1999. / Includes bibliographical references. Also available on the Internet.

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第21453号 / 医博第4420号 / 新制||医||1032(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 渡邉 大, 教授 浅野 雅秀, 教授 林 康紀 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

Unilateral Spastic Cerebral Palsy (USCP) is caused by an early brain lesion in which the Corticospinal Tract (CST), the primary pathway controlling upper extremity (UE) movements, is affected. The CST connectivity after early brain injury (i.e., an ipsilateral, contralateral, or bilateral connectivity) may influence treatment outcomes. Transcranial magnetic stimulation (TMS) is a common method to probe CST connectivity. However, TMS is limited to children without seizures. Mirror movements (MM), an involuntary imitation of movements by one limb during the contralateral limb voluntary movements, are common in USCP. MM may result when both UEs are controlled by the contralesional motor cortex. Here we investigated the relationship between MM and CST connectivity in children with USCP. We hypothesized that stronger MM were associated with an ipsilateral connectivity. Our secondary aim was to investigate whether the amount of MM was reduced after intensive therapy. Thirty-three children with USCP (mean age=9yrs 6mos; MACS: I-III) participated and were randomized to receive 90hrs of unimanual (n=16) or bimanual (n=17) intensive training. Assessments were measured at baseline and immediately after training. We used TMS and diffusion tensor imaging (DTI) to determine the CST connectivity. We used three approaches to quantify MM: 1) behavioral MM assessment during contralateral movements, including hand opening/closing, finger opposition, finger individuation, and finger walking, 2) involuntary grip force oscillations recorded by force transducer (FT) when the contralateral hand performed repetitive pinching, and 3) involuntary muscle contractions measured by electromyography (EMG) when the contralateral hand performed pinching. Results showed that strong MM (scores ≥3) in the more-affected hand while hand opening/closing were associated with an ipsilateral pathway (Fisher's exact test, p= 0.02). This association was not found in the remaining tasks (Fisher’s exact test, opposition, p≥ 0.99; individuation, p≥ 0.99; finger walking, p≥ 0.99). Involuntary GF oscillations were measured in a subset of 16 children. Presence of FT-measured MM in the less-affected hand (> 0.3N) was not associated with TMS-probed connectivity (Fisher’s exact test, p= 0.59). Nevertheless, presence of FT-measured MM was associated with DTI-assessed connectivity (Fisher’s exact test, p= 0.0498). Similarly, presence of EMG-measured MM in the more-affected hand was not associated with TMS-probed connectivity (Fisher’s exact test, p= 0.59). Nevertheless, presence of EMG-measured MM was associated with DTI-assessed connectivity (Fisher’s exact test, p= 0.03). The amount of MM did not change after training (p> 0.06 among all measures). In conclusion, strong MM in the more-affected hand while hand opening/closing may be indicative of an ipsilateral connectivity identified by TMS. Presence of MM measured by FT may be a predictor of DTI-assessed CST pattern. Findings of this study may help researchers and clinicians understand the relationship between the CST connectivity and its behavioral manifestation in children with USCP. Such relationship may further guide therapeutic strategies in a wider range of children with USCP.

Copies of author's previously published articles inserted. / Bibliography: leaves 193-228. / xvi, 235 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / The aim of this thesis is to provide evidence of a training related effect on neural control of a muscle in individuals who have long standing different patterns of use of their muscles. The study examines the motor unit (MU) discharge properties in first dorsal interosseous muscle of individuals who had experienced very different usage patterns of their hand muscles and explores the relationship between different muscle usage patterns and involuntary force fluctuations (tremor). It evaluates the importance of the shared branched-axon inputs to motor neurons in the production of common drive and investigates the relationship between different measures of MU sychronization. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physiology, 1997?

Thesis (Ph. D.)--University of Alabama at Birmingham, 2009. / Title from PDF title page (viewed Mar. 31, 2010). Additional advisors: N. Shastry Akella, James E. Cox, Gitendra Uswatte, Victor W. Mark. Includes bibliographical references (p. 50-60).

To investigate the roles of different dorsal spinal pathways in controlling movements in rats, I performed lesions of specific spinal pathways and measured the behaviour abilities of rats using different sensorimotor behavioural tests. The first experiment was designed to understand the contribution of sensory pathways traveling in the dorsal funiculus during locomotion and skilled movements using sensitive behavioural tests. I demonstrated that ascending sensory fibers play an important role during overground locomotion and contribute to skilled forelimb movements. The second experiment compared the differences in sensorimotor abilities caused by dorsal funicular lesions performed at two different levels of rat spinal cord. My results showed that the pathways present in the cervical and thoracic dorsal funiculus exert different functional effects over control of limb movement during locomotion. The third experiment investigated the compensatory potential of dorsal funicular pathways after dorsolateral funicular injuries in rats. My results showed that dorsal funicular pathways do not compensate for loss of dorsolateral pathways during the execution of locomotor tasks, though there is indirect evidence that rats with dorsolateral funicular lesions might rely more on ascending sensory pathways in the dorsolateral funiculus during skilled forelimb movements. Finally, the fourth experiment was designed to investigate the compensation from dorsolateral funicular pathways after injuries to pyramidal tract in rats. I demonstrated that pathways running in the spinal dorsolateral funiculus do provide compensatory input to spinal circuitry to maintain skilled reaching abilities after lesions of the pyramidal tract but these same pathways do not appear to compensate during either overground locomotion or skilled locomotion. Thus, this compensatory response is task-specific. These results highlight the fact that behavioural context determines the nature of compensation from spared pathways after spinal cord injuries.