Age-based model for metacarpophalangeal joint proprioception in elderly

Figures & data

Figure 1 Side view on the RCM mechanism of the robotic device used to induce passive movements around the MCP joint.

Note: The sequence of pictures shows one trial, during which two different flexion angles (A1 and A2) are presented.
Abbreviations: MCP, metacarpophalangeal; RCM, remote center of motion.

Figure 2 Resulting psychometric functions and PEST sequences of a representative subject.

Notes: (Top) Psychometric functions (thick lines) for both hands of subject S22 (67-year-old male). The size of the black dots indicates the number of presentations of a stimulus at a certain stimulus level (Δ stimulus). (Bottom) Corresponding PEST sequences for the same subject. The thick line represents the stimulus level at each trial.
Abbreviations: DL, difference threshold or limen; PEST, Parameter Estimation by Sequential Testing.

Table 1 Summary of the mixed-effects model analysis with the estimates and their SE predicting the log₁₀DL

Name	Estimate	SE	t-Value	DF	P-value	Confidence interval (95%)		Simulated LRT
						Lower	Upper	P-value
Fixed effects
(Intercept)	−0.857	0.678	−1.27	52	0.212	−2.217	0.503
Agea	0.014	0.005	2.74	52	0.008*	0.004	0.025	0.019*
Sexb	0.142	0.082	1.72	52	0.091	−0.023	0.307	0.115
Finger lengthc	−0.000	0.005	−0.09	52	0.928	−0.011	0.010	0.931
Trialsd	0.002	0.001	1.96	52	0.055	−0.000	0.004	0.085
Tested hande	−0.054	0.085	−0.64	52	0.527	−0.224	0.116	0.801
Measurementf	−0.010	0.083	−0.12	52	0.903	−0.177	0.157	0.724
Measurement*tested hande,f	0.083	0.124	0.67	52	0.507	−0.166	0.331	0.541
Random effects
Group	Name	SD
Subject	(Intercept)	0.048
Residual		0.213

Notes: The last column shows the P-values from the simulated LRT. The fixed effect age affected the DL significantly in increasing direction (*P<0.05).

a Baseline =0 years.

b Baseline = male.

c Baseline =0 mm.

d Baseline =0 trials.

e Baseline = dominant.

f Baseline = first.

Abbreviations: DF, degrees of freedom; DL, difference threshold or limen; LRT, likelihood ratio test; SD, standard deviation; SE, standard error.

Figure 3 Age–DL relationship.

Notes: Aging has a significant increasing effect on the DL (P<0.05). The DL of the dominant hand is indicated by an upward-pointing triangle and the DL of the nondominant by a downward-pointing triangle. Both assessments are connected through a gray vertical line for each subject. Black lines show the age-based DL model (thick line) ±SE (dashed lines) obtained from the mixed-effects model analysis.
Abbreviations: DL, difference threshold or limen; SE, standard error.