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Abstract:
Abstract: In an ongoing test of the hypothesis that the
cerebellum is involved in monitoring and optimizing the acquisition
of information in various sensory modalities, we examined the
effect in humans of cerebellar degeneration on fine auditory
discrimination. Nine patients and nine matched controls performed
pitch and localization discrimination tasks measuring difference
thresholds. The patients had idiopathic, hereditary, or
paraneoplastic cerebellar degeneration, no other known neurological
conditions, and ataxias ranging from minimal to severe. Patients
and controls had mostly normal loudness thresholds; some had mild
hearing loss in the 4000-8000 Hz range. Subjects made forced-choice
discriminations between a 500 Hz standard and higher or lower
comparison tones. They also discriminated between a standard noise
burst presented to each ear simultaneously and left or right
localized comparison bursts (with non-zero interaural time
differences). All stimuli had suprathreshold loudness (80 dB).
Patients' difference thresholds for pitch and auditory localization
were on average five times that for controls (P < 0.005).
The degree of impairment was correlated with the severity of their
ataxia (+0.75), but uncorrelated with their auditory loudness
thresholds. Patients and controls did not differ on digit span
memory. These results suggest that the cerebellum has a fundamental
supporting role in the information processing necessary for fine
auditory discrimination.
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