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Dissertation
Afferent regulation of force-field primitives during real limb behaviors
Doctor of Philosophy (Ph.D.), Medical College of Pennsylvania and Hahnemann University
Feb 2000
DOI:
https://doi.org/10.17918/00009329
Abstract
Spinal interneurons may be organized into functional assemblies that form building blocks for constructing limb movement. Understanding how such assemblies are recruited and used to construct limb behaviors and how sensory feedback supports the operation of these assemblies represent important areas of research. A mathematical framework, which describes the motor output of spinal circuits as a force field, has been developed using the frog as a model preparation. Force-field measurements describe the combined action of a stimulated interneuronal assembly, an activated muscle synergy and sensory feedback across the configuration-space of the hindlimb. A small number of invariant force-field structures and associated muscle synergies were organized in the frog's spinal cord. The invariant field structures were termed 'force-field primitives'. Microstimulation studies showed that force-field primitives could be combined by vector summation and scaled in amplitude to produce a larger range of force-field patterns. It was hypothesized that force-field primitives might form stable building blocks for constructing more complex, natural limb behaviors. The first part of this thesis tests whether a reflex behavior, which is organized at the level of the spinal cord, is constructed by a combination of force-field primitives. The behavior examined is the hindlimb to hindlimb wiping reflex. This behavior requires coordination of muscle activation and of joint torques at the hip and knee to accurately move the endpoint of the hindlimb to a target and to remove the target. Several methods were used to decompose this behavior and correction responses during this behavior into a combination of primitives: (1) natural observations of primitive deletions, (2) perturbations to evoke primitive deletions/additions, and (3) statistical decomposition techniques. The second part of this thesis tests whether sensory feedback regulates the operation of individual primitives, the temporal pattern of primitive activation, and functional aspects of the behavior. Several methods were used including (1) whole-limb and selective deafferentation, (2) selective (muscle vibration) and whole-limb perturbations, and (3) single unit recordings of sensory afferents. The results of this thesis provide strong evidence that reflex behaviors are constructed from primitives and that sensory feedback scales the amplitude and regulates the phasing of primitive activation.
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Details
- Title
- Afferent regulation of force-field primitives during real limb behaviors
- Creators
- William J. Kargo
- Contributors
- Simon F. Giszter (Advisor) - Drexel University, Medical College of Pennsylvania and Hahnemann University (1993-1996, 1998-2002)
- Awarding Institution
- Medical College of Pennsylvania and Hahnemann University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Medical College of Pennsylvania and Hahnemann University; Philadelphia, Pennsylvania
- Number of pages
- ix, 384 pages
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- Medical College of Pennsylvania and Hahnemann University (1993-1996, 1998-2002)
- Other Identifier
- 991021888831804721