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Biomedical subjects

A J Benson

Publications and source records attributed to A J Benson.

At least 37 records · Page 2Linked to original sources
PubMed1978

Voluntary movement control and adaptation to cross-coupled stimulation.

The rates at which protective adaptation was acquired to an incremental cross-coupled stimulus were compared under three conditions of movement control: 1) a passive condition in which the 45 degree lateral tilts of the subject's chair were controlled entirely by the experimenter (N = 12); 2) an active condition in which the same movements were achieved directly through the subject's own muscular effort (N = 12); and 3) an active-passive condition in which control was exercised indirectly through microswitches located on the chair arms (N = 12). Adaptation was measured by the rate of neutralization of the oculogyral illusion, as estimated from the apparent motion of a small, dimly illuminated target. The results supported the prediction that the passive condition would be the least effective mode for acquiring adaptation. An unexpected finding was that the active-passive condition proved to be the most efficient for the development of adaptation.

Adaptation, Physiological↗
PubMed1977

Incidence of salmonella infection in animals in England and Wales 1968--1974.

Of a total of 23,609 incidents of salmonella infection reported during the period 1968--74, 20,326 occurred in cattle, 1744 in poultry and other birds, 675 in sheep, 558 in pigs and 306 in other species of animals. Despite the large number of serotypes isolated (153), 88% of incidents were due to only two stereotypes: S. dublin (15,929 incidents of which 15,446 occurred in cattle ) and S. typhimurium (4842 incidents of which 3785 occurred in cattle and 732 in birds). S. choleraesuis was the third (314 incidents which with only 5 exceptions occurred in pigs) and S. abortusovis (243 incidents all in sheep) was the fourth most commonly isolated serotype. The following six serotypes were each recorded in more than 100 incidents: S. newport (177), S. agona (170), S. virchow (169), S. anatum (152), S. enteritidis (150) and S. montevideo (111). The other 143 serotypes accounted for only 5-8% of total incidents. The trends of annual incidence of salmonella infection in cattle, sheep, pigs, poultry and other birds during the 17-year period 1958-74 and the distribution of the main serotypes in the individual species of animals from 1968 to 1974 are discussed.

Animals↗
PubMed1973

Body sway induced by a low frequency alternating current.

A sine wave current stimulus, applied between electrodes placed about one ear and an indifferent electrode, produced a cyclical sway predominantly in the coronal plane. In 12 normal subjects, stimulus frequency (0.1-0.6 Hz) and intensity (+/-0.05 - +/-1.5 mA) had no significant effect on the amplitude of the postural response, but phase lag increased from 0.7 rad at 0.1 Hz to 3.8 rad at 0.6 Hz. Stimulation at 0.3 Hz, +/-1.0 mA evoked detectable responses in all but one of 50 normal subjects. Seven patients with end organ lesions all gave positive responses with the same test procedure. Likewise 13 out of 16 patients with destruction of the VIII nerve also gave positive responses. In the other 3 patients the response on the side of the lesion was absent, as it was in another 3 individuals with lesions of the vestibular nuclei. It was concluded that the sway induced by a low frequency alternating current is the manifestation of the stimulation of structures within the CNS central to the vestibular nerve or its end organ.

Electric Stimulation↗
PubMed1970

Response of semicircular canal dependent units in vestibular nuclei to rotation of a linear acceleration vector without angular acceleration.

1. Recent experiments have shown that rotation of a linear acceleration vector round the head can generate involuntary ocular nystagmus in the absence of angular acceleration. The present experiments examine the suggestion that adequate stimulation of the semicircular canals may contribute to this response.2. Decerebrate cats were located in a stereotaxic device on a platform, slung from four parallel cables, which could be driven smoothly round a circular orbit without inducing significant angular movement of the platform. This Parallel Swing Rotation (PSR) generated a centripetal acceleration of 4.4 m/sec(2) which rotated round the head at 0.52 rev/sec.3. The discharge frequency of specifically lateral canal-dependent neural units in the vestibular nuclei of cats was recorded during PSR to right and left, and in the absence of motion. The dynamic responses to purely angular motion were also examined on a servo-driven turntable.4. Without exception all proven canal-dependent cells examined (twenty-nine cells in nine cats) were more active during PSR in the direction of endolymph circulation assessed to be excitatory to the unit, than during PSR in the opposite direction.5. The observed changes in discharge frequency are assessed to have been of a magnitude appropriate for the generation of the involuntary oculomotor response induced by the same stimulus in the intact animal.6. The findings suggest that a linear acceleration vector which rotates in the plane of the lateral semicircular canals can be an adequate stimulus to ampullary receptors, though an explanation which invokes the modulation of canal cells by a signal dependent upon the sequential activation of macular receptors cannot be positively excluded.

Acceleration↗