Postural Perceptions and Eye Displacements Produced by a Resultant Vector Acting in the Median Sagittal Plane of the Head: 1. Responses along Three Axes by Stepwise Increasing ϕ with the Subject Heading Centripetally in an Erect and a Tilted Position

Abstract

Applying a previously described centrifuge-test method, the changes of position in space of an observed visual object were recorded by naïve subjects exposed in darkness to a resultant vector, acting in the sagittal plane of their heads, and systematically referred to the same plane of reference (frontal plane). Simultaneously, the torsional changes of the eye were determined by means of an IR filming procedure. A comparison was made between the two responses in two attitudes, i.e., one strictly vertical, and one with the same subject tilted outwards, in both cases facing the centre, in respect to a stepwise increasing force field with angular acceleration reduced to negligible quantities. This permits the conclusion that an (apparent) displacement of the target, which occurs chiefly in a headward direction, is generally associated with a countertorsion of the eye in the opposite direction, and that the ocular change is far inferior in size to the corresponding visual phenomenon. Marked discrepancies are often noted between the pattern of the two responses, which nevertheless remain in a certain relation to the direction and magnitude of the acting force. The results seem to demonstrate the contribution to the total input of the visual and non-visual cues in their repercussions on the consciousness.