Matching Items (4)
Filtering by
- All Subjects: Motor Cortex
- All Subjects: Arm Configuration
- Creators: Dounskaia, Natalia
- Creators: Rahman, Qasim
- Member of: Theses and Dissertations
- Status: Published
Description
Motor behavior is prone to variable conditions and deviates further in disorders affecting the nervous system. A combination of environmental and neural factors impacts the amount of uncertainty. Although the influence of these factors on estimating endpoint positions have been examined, the role of limb configuration on endpoint variability has been mostly ignored. Characterizing the influence of arm configuration (i.e. intrinsic factors) would allow greater comprehension of sensorimotor integration and assist in interpreting exaggerated movement variability in patients. In this study, subjects were placed in a 3-D virtual reality environment and were asked to move from a starting position to one of three targets in the frontal plane with and without visual feedback of the moving limb. The alternating of visual feedback during trials increased uncertainty between the planning and execution phases. The starting limb configurations, adducted and abducted, were varied in separate blocks. Arm configurations were setup by rotating along the shoulder-hand axis to maintain endpoint position. The investigation hypothesized: 1) patterns of endpoint variability of movements would be dependent upon the starting arm configuration and 2) any differences observed would be more apparent in conditions that withheld visual feedback. The results indicated that there were differences in endpoint variability between arm configurations in both visual conditions, but differences in variability increased when visual feedback was withheld. Overall this suggests that in the presence of visual feedback, planning of movements in 3D space mostly uses coordinates that are arm configuration independent. On the other hand, without visual feedback, planning of movements in 3D space relies substantially on intrinsic coordinates.
ContributorsRahman, Qasim (Author) / Buneo, Christopher (Thesis director) / Helms Tillery, Stephen (Committee member) / Barrett, The Honors College (Contributor) / Harrington Bioengineering Program (Contributor)
Created2014-05
Description
Motor behavior is prone to variable conditions and deviates further in disorders affecting the nervous system. A combination of environmental and neural factors impacts the amount of uncertainty. Although the influence of these factors on estimating endpoint positions have been examined, the role of limb configuration on endpoint variability has been mostly ignored. Characterizing the influence of arm configuration (i.e. intrinsic factors) would allow greater comprehension of sensorimotor integration and assist in interpreting exaggerated movement variability in patients. In this study, subjects were placed in a 3-D virtual reality environment and were asked to move from a starting position to one of three targets in the frontal plane with and without visual feedback of the moving limb. The alternating of visual feedback during trials increased uncertainty between the planning and execution phases. The starting limb configurations, adducted and abducted, were varied in separate blocks. Arm configurations were setup by rotating along the shoulder-hand axis to maintain endpoint position. The investigation hypothesized: 1) patterns of endpoint variability of movements would be dependent upon the starting arm configuration and 2) any differences observed would be more apparent in conditions that withheld visual feedback. The results indicated that there were differences in endpoint variability between arm configurations in both visual conditions, but differences in variability increased when visual feedback was withheld. Overall this suggests that in the presence of visual feedback, planning of movements in 3D space mostly uses coordinates that are arm configuration independent. On the other hand, without visual feedback, planning of movements in 3D space relies substantially on intrinsic coordinates.
ContributorsRahman, Qasim (Author) / Buneo, Christopher (Thesis director) / Helms Tillery, Stephen (Committee member) / Barrett, The Honors College (Contributor) / Harrington Bioengineering Program (Contributor)
Created2014-05
Description
Navigation through natural environments requires continuous sensory guidance. In addition to coordinated muscle contractions of the limbs that are controlled by spinal cord, equilibrium, body weight bearing and transfer, and avoidance of obstacles all have to happen while locomotion is in progress and these are controlled by the supraspinal centers.
For successful locomotion, animals require visual and somatosensory information. Even though a number of supraspinal centers receive both in varying degrees, processing this information at different levels of the central nervous system, especially their contribution to visuo-motor and sensory-motor integration during locomotion is poorly understood.
This dissertation investigates the patterns of neuronal activity in three areas of the forebrain in the cat performing different locomotor tasks to elucidate involvement of these areas in processing of visual and somatosensory information related to locomotion. In three studies, animals performed two contrasting locomotor tasks in each and the neuronal activities were analyzed.
In the first study, cats walked in either complete darkness or in an illuminated room while the neuronal activity of the motor cortex was recorded. This study revealed that the neuronal discharge patterns in the motor cortex were significantly different between the two illumination conditions. The mean discharge rates, modulation, and other variables were significantly different in 49% of the neurons. This suggests a contextual correlation between the motor cortical activity and being able to see.
In two other studies, the activities of neurons of either the somatosensory cortex (SI) or ventrolateral thalamus (VL) were recorded while cats walked on a flat surface (simple locomotion) or along a horizontal ladder where continuous visual and somatosensory feedback was required (complex locomotion).
We found that the activity of all but one SI cells with receptive fields on the sole peaked before the foot touched the ground: predictably. Other cells showed various patterns of modulation, which differed between simple and complex locomotion. We discuss the predictive and reflective functionality of the SI in cyclical sensory-motor events such as locomotion.
We found that neuronal discharges in the VL were modulated to the stride cycle resembling patterns observed in the cortex that receives direct inputs from the VL. The modulation was stronger during walking on the ladder revealing VL’s contribution to locomotion-related activity of the cortex during precision stepping.
For successful locomotion, animals require visual and somatosensory information. Even though a number of supraspinal centers receive both in varying degrees, processing this information at different levels of the central nervous system, especially their contribution to visuo-motor and sensory-motor integration during locomotion is poorly understood.
This dissertation investigates the patterns of neuronal activity in three areas of the forebrain in the cat performing different locomotor tasks to elucidate involvement of these areas in processing of visual and somatosensory information related to locomotion. In three studies, animals performed two contrasting locomotor tasks in each and the neuronal activities were analyzed.
In the first study, cats walked in either complete darkness or in an illuminated room while the neuronal activity of the motor cortex was recorded. This study revealed that the neuronal discharge patterns in the motor cortex were significantly different between the two illumination conditions. The mean discharge rates, modulation, and other variables were significantly different in 49% of the neurons. This suggests a contextual correlation between the motor cortical activity and being able to see.
In two other studies, the activities of neurons of either the somatosensory cortex (SI) or ventrolateral thalamus (VL) were recorded while cats walked on a flat surface (simple locomotion) or along a horizontal ladder where continuous visual and somatosensory feedback was required (complex locomotion).
We found that the activity of all but one SI cells with receptive fields on the sole peaked before the foot touched the ground: predictably. Other cells showed various patterns of modulation, which differed between simple and complex locomotion. We discuss the predictive and reflective functionality of the SI in cyclical sensory-motor events such as locomotion.
We found that neuronal discharges in the VL were modulated to the stride cycle resembling patterns observed in the cortex that receives direct inputs from the VL. The modulation was stronger during walking on the ladder revealing VL’s contribution to locomotion-related activity of the cortex during precision stepping.
ContributorsNilaweera, Wijitha Udayalal (Author) / Beloozerova, Irina N (Thesis advisor) / Smith, Brian H. (Thesis advisor) / Dounskaia, Natalia (Committee member) / Vu, Eric (Committee member) / Arizona State University (Publisher)
Created2016
Description
Locomotion in natural environments requires coordinated movements from multiple body parts, and precise adaptations when changes in the environment occur. The contributions of the neurons of the motor cortex underlying these behaviors are poorly understood, and especially little is known about how such contributions may differ based on the anatomical and physiological characteristics of neurons. To elucidate the contributions of motor cortical subpopulations to movements, the activity of motor cortical neurons, muscle activity, and kinematics were studied in the cat during a variety of locomotion tasks requiring accurate foot placement, including some tasks involving both expected and unexpected perturbations of the movement environment. The roles of neurons with two types of neuronal characteristics were studied: the existence of somatosensory receptive fields located at the shoulder, elbow, or wrist of the contralateral forelimb; and the existence projections through the pyramidal tract, including fast- and slow-conducting subtypes.
Distinct neuronal adaptations between simple and complex locomotion tasks were observed for neurons with different receptive field properties and fast- and slow-conducting pyramidal tract neurons. Feedforward and feedback-driven kinematic control strategies were observed for adaptations to expected and unexpected perturbations, respectively, during complex locomotion tasks. These kinematic differences were reflected in the response characteristics of motor cortical neurons receptive to somatosensory information from different parts of the forelimb, elucidating roles for the various neuronal populations in accommodating disturbances in the environment during behaviors. The results show that anatomical and physiological characteristics of motor cortical neurons are important for determining if and how neurons are involved in precise control of locomotion during natural behaviors.
Distinct neuronal adaptations between simple and complex locomotion tasks were observed for neurons with different receptive field properties and fast- and slow-conducting pyramidal tract neurons. Feedforward and feedback-driven kinematic control strategies were observed for adaptations to expected and unexpected perturbations, respectively, during complex locomotion tasks. These kinematic differences were reflected in the response characteristics of motor cortical neurons receptive to somatosensory information from different parts of the forelimb, elucidating roles for the various neuronal populations in accommodating disturbances in the environment during behaviors. The results show that anatomical and physiological characteristics of motor cortical neurons are important for determining if and how neurons are involved in precise control of locomotion during natural behaviors.
ContributorsStout, Eric (Author) / Beloozerova, Irina N (Thesis advisor) / Dounskaia, Natalia (Thesis advisor) / Buneo, Christopher A (Committee member) / Santello, Marco (Committee member) / Arizona State University (Publisher)
Created2015