Richard D. Gilson

COMPARISON OF SUBJECTIVE RESPONSES TO SEMICIRCULAR CANAL STIMULATION PRODUCED BY ROTATION ABOUT DIFFERENT AXES

A procedure has been developed for obtaining reliable measures of sensation associated with semicircular canal stimulation. Theoretically these measures can be used along with measures of nystagmiis to estimate several vestibular response system parameters. In this experiment, responses produced by stimulation of the horizontal semicircular canals are compared with those produced by stimulation of the vertical canals. Group mean estimates of subjective angular displacement obtained from forty US Navy flight students were approximately accurate for stimulation of both horizontal and vertical canals. Significant individual differences were found within the group. From the responses obtained, mean estimates of vestibular system parameters were calculated. The method appears to be a practical means of measuring the K. (θ/Δ) parameter which has not been assessed in the past due to lack of a suitable method.

Effects of alcohol ingestion on tracking performance during angular acceleration.

Abstract : Most studies of the effects of alcohol on human performance involve static (absence of motion) situations. However, the addition of motion, involved in such activities as piloting an aircraft, might well produce impairments not usually obtained in static situations. The present study examined some of the effects of alcohol ingestion on visual tracking performance (eye-hand coordination) during angular acceleration. Following practice and base-line tests of tracking performance in both static (stationary) and dynamic (whole body angular acceleration) conditions, 10 subjects received orange juice which contained 2.0 ml of 100-proof vodka per kg of subject weight; another 10 drank orange juice with a few drops of rum extract added. Tests, conducted 1, 2, 4, 8, and 10 hours after drinking, were in total darkness with the exception of the visual display which was illuminated to recommended levels for cockpit instruments. Static tracking errors for Alcohol subjects were significantly higher than those of Control subjects only at the 4-hour session. However, Alcohol subjects made significantly more dynamic tracking errors than Controls during the 1-, 2-, and 4-hour sessions. These data suggest that eye-hand coordination may show little or no impairment following alcohol ingestion in static situations, yet may be seriously degraded during motion. (Author)

Nystagmus Responses During Triangular Waveforms of Angular Velocity About the Y- and Z-Axes.

Nystagmus slow phase velocity was measured during rotation stimuli consisting of short (12 sec) triangular waveforms of angular velocity. In one test series the horizontal semicircular canals were stimulated and in another test series the vertical canals were stimulated. The data were fit by equations derived from the assumption that the responses depend upon a cupula-endolymph system that responds like an over critically damped torsion pendulum. Mean long time constant (II/δ) values found for the horizontal and vertical canal responses were, respectively, 16 sec and 7 sec, consistent with previous findings, whereas “gain” constants found for the horizontal and vertical canals were, respectively, 8.0 sec and 5.4 sec. Procedures for quickly extracting these parametric values from nystagmus records are described and, for practical reasons, the effects of stimulus distortion on the estimates of parameters were also considered.