Impact of Prolonged Temporal Discrimination Threshold on Finger Movements of Parkinson's Disease

Abstract

Introduction: Sensory information is essential for the precise control of movement. Patients with Parkinson's disease (PD) have higher-order sensory dysfunctions including prolonged temporal discrimination threshold (TDT). However, the impact of prolonged TDT on parkinsonian motor deficits is uncertain.

Methods: This study includes 33 PD patients and 24 healthy controls. TDT values were measured in the index finger. Using coin rotation task (CRT), dexterous finger movement was assessed. Using an inertial sensor, the speed, amplitude, and frequency of finger tapping were measured. The impact of prolonged index finger TDT on two different finger movements was analyzed using the general estimating equation.

Results: Compared to healthy controls, TDT was prolonged in the PD patients. There was no impact of TDT on mean values or decrement for amplitude and speed, as well as mean values, decrement and variability of tapping frequency. However, prolonged TDT had a significant impact on the variability in amplitude (B = 436.905 × 10-4, Wald χ2 = 9.140, p = 0.014) and speed (B = 425.655 × 10-4, Wald χ2 = 9.876, p = 0.014) of finger tapping. There was a marginal correlation between TDT and CRT. In addition, CRT correlated with variability in amplitude and speed of finger tapping.

Conclusion: In PD, cutaneous temporal discriminative sensory dysfunction appears to be related to increased variabilities in the speed and amplitude of fast repetitive finger movements and disturbed finger dexterity.

Fig 1. Scatter plots showing the relationship between TDT values and finger movement-related parameters in PD group.

Slope-related parameters were transformed to positive values by adding a constant (+10). Open circles represent the left side hand and filled circles represent the right side hand. The fitted line represents the predicted mean response in the GEE model (predictor = TDT values, response = finger movement-related parameters), and the shaded area indicates 95% confidence interval. TDT = temporal discrimination threshold; CoV = coefficient of variance)

Fig 2. Scatter plots showing the relationship between TDT values and finger movement-related parameters in control group.

Slope-related parameters were transformed to positive values by adding a constant (+10). Open circles represent the left side hand and filled circles represent the right side hand. The fitted line represents the predicted mean response in the GEE model (predictor = TDT values, response = finger movement-related parameters), and the shaded area indicates 95% confidence interval. TDT = temporal discrimination threshold; CoV = coefficient of variance)

Fig 3. Scatter plots in the PD (A) and control (B) groups showing the relationship between CR scores and variabilities in amplitude and speed.

Open circles represent the left side hand, and filled circles represent the right side hand. The fitted line represents the predicted mean response in the GEE model (predictor = TDT values, response = variabilities in amplitude and speed), and the shaded area indicates 95% confidence interval. CR = coin rotation; CoV = coefficient of variance.