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Biomedical subjects

A J Benson

Publications and source records attributed to A J Benson.

6 recordsLinked to original sources
PubMed1978

Coriolis cross-coupling effects: disorienting and nauseogenic or not?

Nausea and disorientation are sometimes produced by head movements during turning maneuvers in aircraft. These responses are usually attributed to Coriolis cross-coupling stimulation of the vestibular system, although it has been indicated recently that many turning maneuvers of aircraft have insufficient angular velocity to generate such effects. The purpose of the present study was to further distinguish conditions in which Coriolis cross-coupling effects are disorienting and nauseogenic from conditions in which they are neither.

Adult↗
PubMed1978

Vision during angular oscillation: the dynamic interaction of visual and vestibular mechanisms.

A review is presented of the dynamic behaviour of two oculomotor control systems--the vestibulo-ocular and pursuit reflexes--responsible for the spatial and temporal stabilization of the image of an observed object on the fovea of the retina, and mathematical models adduced in which the contribution of physiological components of the systems can be identified. With angular oscillation of the head below 1-2 Hz, retinal information is used to maintain unity gain of the head/eye system, but at higher frequencies stabilization is determined primarily by vestibular inputs. When the observed target moves with the head, as in a head-mounted display, the suppression of inappropriate vestibulo-ocular responses is dependent upon the dynamic performance of the pursuit system. With such a display, impairment of visual acuity may be detected at frequencies of oscillation as low as 0.5 Hz.

Humans↗
PubMed1978

Visual-vestibular interaction in the control of eye movement.

Three experimental conditions have been used to investigate the extent to which inappropriate reflex eye movements of vestibular origin can be suppressed by visual feedback. First, the ability to read digits in a display which moved with the head was assessed during angular oscillation about the yaw and pitch axes of the body. Performance decrement was observed at frequencies above 0.2 Hz in pitch and 1.0 Hz in yaw, being greater at higher stimulus velocity levels. A second experiment revealed that the performance decrement was associated with eye movements relative to the head, which increased with the frequency of stimulation. Finally, the response of the pursuit reflex was investigated under similar experimental conditions. The results indicated that the breakdown in the pursuit reflex and in the suppression of the vestibulo-ocular reflex occurred over the same frequency band, implying the similarity of the mechanisms responsible for suppression and pursuit.

Aerospace Medicine↗
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↗