No abstract

Eight patients with absent vestibular function categorized into four grades according to the disability they suffered from oscillopsia have been studied with a view to correlating its severity with the development of gaze stabilizing compensatory mechanisms. Eye movements were recorded while the following sinusoidal rotational stimuli were delivered: 1) trunk on head oscillation in the dark (COR); 2) head on trunk oscillation in the dark; 3) head on trunk and whole body (head and trunk) oscillation in the light in the presence of optic fixation. The COR was potentiated in all the patients regardless of their clinical status. Velocity gains (peak slow phase eye velocity/peak head velocity) during whole body rotation were significantly lower than head on trunk gains in the light in the better compensated patients. Since in the absence of vestibular function whole body rotation involves only the otokinetic system (OKN), this finding implies a depression of the OKN in these patients which can be corrected during head on trunk movements by virtue of a dynamic input from the neck. The results suggest that the processes of recovery from oscillopsia are dependent, in the main, upon the development of central mechanisms by means of which undesirable image movement across the retina is perceptually suppressed. Depression of OKN may be secondary to this perceptual rearrangement.

A variety of experimental situations are described concerning optokinetic nystagmus and tracking movements of the eyes, which have shown that in certain circumstances the peripheral retina can exert a powerful influence upon the resultant response. The teleological significance of the findings is discussed in the context of the mechanisms subserving ocular-following movements.

WHEREAS the technique of air conduction audiometry is well established, the basic principles of bone conduction audiometry are still far from being generally understood. In consequence, the tests are still too often inefficiently performed, and hence fail to provide the vital diagnostic information which is their purpose.As will be shown, this disappointing state of affairs is quite unnecessary, and requires for its correction no more than a rational standardization of our technical equipment and test procedures, whereby proper use is made of the considerable body of acoustic and physiological knowledge now at our disposal.An essential requirement with all bone conduction tests is the exclusion of the untested ear