Spinocerebellar ataxias (SCAs) are a group of autosomal dominantly inherited degenerative diseases. As the pathological process probably commences years before the first appearance of clinical symptoms, preclinical carriers of a SCA mutation offer the opportunity to study the earliest stages of cerebellar dysfunction and degeneration.
To study the earliest stages of cerebellar dysfunction an eye blink test is performed in 18 preclinical carriers of a SCA3 mutation and 16 healthy, age-matched controls. The participants were presented with repeated pairings of an auditory tone with a supraorbital nerve stimulus with a delay interval of 400 ms.
Preclinical carriers acquired significantly less conditioned eyeblink responses than controls and learning rates were significantly reduced. This motor learning defect was, however, not associated with the predicted time to onset.