Sensation Of Changes Research Articles

Visual Sensations of Roll Rotation During Complex Vestibular Stimulation

In aviation, vestibular-induced spatial disorientation is a significant cause of accidents. Recreating flight-like vestibular stimuli in simulators might be a means for training pilots to respond adequately in disorienting situations. Due to the physical constraints of land-based simulators, the question arises whether a given illusion may be created in different ways. For instance, is it possible to induce sensations of tilt by rotary stimuli? The present study concerns the relationship between sensations of rotation and tilt during complex vestibular stimulation. The visual sensation of roll rotation was quantified by means of a velocity-matching procedure. In a large gondola centrifuge eight subjects underwent four runs (2 G, 2 min) with different heading positions (forward, backward, centripetally, and centrifugally). The inclination of the gondola persistently corresponded with the vector sum of the Earth gravity force and the centrifugal force (60 degrees at 2 G). Thus, the semicircular canal stimulus in roll was combined in different ways with stimuli in yaw and pitch, as well as with an increasing or decreasing G vector. The magnitude of the responses was only dependent on the roll component of the stimulus. The gain, defined as the ratio between the response and the roll stimulus, was 7-10%. The responses decayed with a time constant ranging from 4 to 5.5 s. The visual sensation of roll rotation reflects the roll plane canal velocity stimulus independently of other stimulus components. This is in contrast to earlier findings on the sensation of changes in position (roll tilt).

Magnitude of the Plan

The National Plan may involve deficit financing of 200 crores if no further foreign assistance is forthcoming. In the State Plan, the propor- tion of prospective items is even larger. Nonetheless, it is criticised that the finances of the plan are of a small order, the total increase in expenditure being stated by the Commission to be an increase of only 10 per cent of the current year's figures, as against an increase of 100 per cent which has taken place since 1947. It is argued that from such expenditure the "sensation of change", which the Prime Minister con- sidered necessary to transform the attitude of the people, cannot be expected.