FREQUENCY-CHARACTERISTICS OF ACCOMMODATION IN A PATIENT WITH AGENESISOF THE POSTERIOR VERMIS AND NORMAL SUBJECTS

Aims-To clarify the cerebellar control of accommodation in humans, the frequency characteristics of accommodation were studied in a patient with agenesis of the posterior cerebellar vermis and four age matched normal subjects. Methods-Magnetic resonance imaging of the brain of th e 29 year old patient showed agenesis of the vermis and paravermis of lobules VIII-X and hypoplasia of the vermis and paravermis of lobules I-VII, the cerebellar hemisphere, and the cerebellar nuclei, The gain and phase lag of accommodative responses for sinusoidally modulated bl ur stimuli were calculated for the patient and four normal subjects. T he blur stimuli consisted of predictable simple sinusoids of 3.0 diopt res at a frequency of 0.05, 0.1, 0.2, 0.3, 0.5, or 1.0 Hz, Results-The frequency characteristics of accommodative responses in the patient h ave a larger phase lag and a smaller gain at higher frequencies than t hose in the four normal subjects. Conclusions-These findings suggest t hat the cerebellum contributes to the control of accommodation by impr oving the the frequency characteristics at high frequencies.