One-year reliability of vibration sensitivity thresholds in human beings

Vibration sensitivity of the 3rd and 5th digits was evaluated in 36 female volunteers (between 22 and 36 years of age at the beginning of the study) previously screened for the absence of neurological disorders. Both fingers were tested in the same subjects on weeks 1, 2 and 52 in a balanced crossover design. Twenty-nine volunteers completed all 3 sessions. All participants gave their informed consent prior to participation. The test session was divided into trials. Each trial consisted of 2 sequential intervals, identified by a signal, and vibration was applied to the fingertip during either the first or the second interval. The subject was instructed to press the push button corresponding to the interval that contained vibration (two-interval forced-choice procedure). Vibration amplitudes were varied according to the up-down transformed rule for the estimation of the amplitude corresponding to 75% correct detection. Vibration sensitivity thresholds were stable as reflected by the lack of a trend over time, and by the compound symmetry of the variance-covariance matrix, which reflects stability of threshold variances as well as of intersession correlations over time. Reliability of vibration sensitivity makes this test potentially suitable for longitudinal evaluation of somatosensory functions.