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A Garfinkel

Publications and source records attributed to A Garfinkel.

59 records · Page 4Linked to original sources
PubMed1990

Spatial distribution of muscle fibers within the territory of a motor unit.

The spatial distribution of muscle fibers belonging to a motor unit was studied in the soleus (SOL) and tibialis anterior (TA) of adult cats to provide a detailed description of the spatial patterns which exist within the territory of a motor unit. Glycogen depletion of the motor unit was achieved through repetitive stimulation of either the intracellularly identified motoneuron or the functionally isolated motor axon. Muscle fibers belonging to the stimulated unit were identified in serial cross-sections, and in the cross-section which contained the most depleted fibers the centroid of each depleted fiber was determined. Subsequently, three spatial analyses, ie, a quadrat analysis, a point-to nearest neighbor analysis and an interfiber distance analysis, were used to determine if motor unit fibers were distributed randomly throughout the territory of the unit. Motor unit fibers tended to be localized within the muscle cross-section and were not evenly or homogeneously distributed throughout the territory. In general, the analyses suggested that motor unit fibers may be arranged in clusters or subgroups of varying size. The data demonstrate three different quantitative analyses for studying the organization of muscle fibers of normal motor units, which can be used for objective assessment and diagnosis of neuromuscular diseases.

Animals↗
PubMed1989

Qualitative dynamics of disordered human locomotion: a preliminary investigation.

A qualitative approach to the evaluation of disordered locomotion is introduced within the framework of dynamical systems theory. Exemplar phase plane and angle-angle plots of knee and ankle movements were constructed from limb trajectories of neurologically impaired individuals and qualitatively compared with similar plots, reflecting normal locomotion. In phase plane trajectories of normal locomotion, characteristics of spring-like dynamics dominated the loading and unloading phases whereas those of ballistic pendular dynamics were seen during swing. The overall squareness of the normal phase plane trajectories suggested precisely timed and narrowly focused controls. in contrast, phase plane records from hemiparetic subjects had markedly reduced segmental velocities, pronounced velocity reversals in both stance and swing, and a loss of overall squareness. Knee-ankle plots of normal locomotion revealed important features of intersegmental coordination such as coupled out-of-phase coordination in loading and unloading, a decoupled phase offset in early swing, and a kind of active partitioning in late swing in which one segment moved while the other remained constant. These intersegmental relations were absent or distorted in the hemiparetic angle-angle plots. It is suggested that this qualitative approach, together with electromyography and force dynamics, may allow the characterization of the movement disorders associated with given neuropathologies.

Journal Article↗
PubMed1988

Spatial distribution of motor unit fibers in the cat soleus and tibialis anterior muscles: local interactions.

The spatial distribution of muscle fibers belonging to a motor unit was studied in the soleus and tibialis anterior muscles of adult cats. Motor unit fibers were depleted of their glycogen through repetitive stimulation of the motoneuron or of the functionally isolated motor axon. Subsequently, the position of depleted muscle fibers was mapped on serial cross sections taken along the length of the muscle. A subset of fibers was selected from the cross section containing the largest number of motor unit fibers and 4 spatial analyses were performed. These analyses were designed to determine whether the muscle fibers belonging to a single unit were distributed in a random manner. To test whether the actual distribution was other than random, Monte Carlo techniques were used to simulate the random innervation of a muscle. From these simulations, a test statistic was calculated for comparison with the observed data. Adjacency and nearest-neighbor analyses revealed no tendency for grouping or dispersion of fibers belonging to a motor unit. However, measurement of the distances between all motor unit fibers revealed a greater tendency for grouping than spreading, suggesting the existence of some mechanism that restricts the absolute distribution and territory of a motor unit.

Animals↗
PubMed1983

A mathematics for physiology.

Nonlinear dynamics gives us a language within which to express the basic concepts of physiology. Form, qualitative change, oscillation, stability, and other biologically important notions find natural expressions in this new mathematical approach. An introduction to qualitative dynamics is sketched, its relevance to physiology is argued, and several examples of its usefulness in providing models and metaphors for describing brain activity are offered.

Animals↗