Relationship Between Body-Specific Attention to a Paretic Limb and Real-World Arm Use in Stroke Patients: A Longitudinal Study

Abstract

Learned nonuse is a major problem in upper limb (UL) rehabilitation after stroke. Among the various factors that contribute to learned nonuse, recent studies have focused on body representation of the paretic limb in the brain. We previously developed a method to measure body-specific attention, as a marker of body representation of the paretic limb and revealed a decline in body-specific attention to the paretic limb in chronic stroke patients by a cross-sectional study. However, longitudinal changes in body-specific attention and paretic arm use in daily life (real-world arm use) from the onset to the chronic phase, and their relationship, remain unknown. Here, in a longitudinal, prospective, observational study, we sought to elucidate the longitudinal changes in body-specific attention to the paretic limb and real-world arm use, and their relationship, by using accelerometers and psychophysical methods, respectively, in 25 patients with subacute stroke. Measurements were taken at baseline (T_BL), 2 weeks (T_2w), 1 month (T_1M), 2 months (T_2M), and 6 months (T_6M) after enrollment. UL function was measured using the Fugl-Meyer Assessment (FMA) and Action Research Arm Test (ARAT). Real-world arm use was measured using accelerometers on both wrists. Body-specific attention was measured using a visual detection task. The UL function and real-world arm use improved up to T_6M. Longitudinal changes in body-specific attention were most remarkable at T_1M. Changes in body-specific attention up to T_1M correlated positively with changes in real-world arm use up to T_6M, and from T_1M to T_6M, and the latter more strongly correlated with changes in real-world arm use. Changes in real-world arm use up to T_2M correlated positively with changes in FMA up to T_2M and T_6M. No correlation was found between body-specific attention and FMA scores. Thus, these results suggest that improved body-specific attention to the paretic limb during the early phase contributes to increasing long-term real-world arm use and that increased real-world use is associated with the recovery of UL function. Our results may contribute to the development of rehabilitation strategies to enhance adaptive changes in body representation in the brain and increase real-world arm use after stroke.

Keywords: accelerometer; body representation; body-specific attention; learned nonuse; recovery; rehabilitation; stroke; upper limb.

Figure 1

(A) The measurement of body-specific attention to the paretic hand. (B) Experimental conditions and definition of body-specific attention (each condition is circled by a solid line; dummy or paretic hand reaction time is circled by a dotted-line). These schematic views show the hand-L and hand-R conditions for patients with left hemiparesis. The patients placed their paretic hand either on the left side (hand-L) or right side (hand-R). In both conditions, the dummy hand was placed on the opposite side of the midline to the paretic hand. For patients with right hemiparesis, the paretic hand was placed to the left of the midline in the hand-L condition and to the right of the midline in the hand-R condition. We defined the amount of body-specific attention directed to the paretic hand as the average reaction time for when the visual target was presented on the dummy hand minus the average reaction time for when the visual target was presented on the paretic hand (body-specific attention = dummy hand − paretic hand). (C) Visual detection task. After the presentation of a fixation point, the visual target appeared randomly from 800 to 1,600 ms, on one of the two hands (paretic or dummy hand). Participants pushed the button only when a blue-filled circle appeared.

Figure 2

Upper limb function. (A) Fugl-Meyer Assessment (FMA). (B) Action Research Arm Test (ARAT). Upper limb function and ability to manipulate objects improved up to 2 months and were maintained up to 6 months (One-factor repeated-measures analysis of variance (ANOVA), multiple comparison procedure: Bonferroni correction. ^*p < 0.05, ^**p < 0.01).

Figure 3

(A) Real-world arm use (use ratio). The real-world arm use increased up to 1 month and improved slowly up to 6 months (one-factor repeated-measures ANOVA, multiple comparison procedure: Bonferroni correction. ^*p < 0.05, ^**p < 0.01). (B) Body-specific attention: longitudinal changes in body-specific attention were highly individual and not significant, but based on mean values, the body-specific attention was maximum at 1 month. The gray area represents the mean ± SD of the index of body facilitation effect in healthy controls.

Figure 4

Relationship between real-world arm use and body-specific attention. (A) There was a positive correlation between the changes in body-specific attention from baseline to 1 month and the changes in the real-world arm use from baseline to 6 months (r = 0.491, p = 0.013). (B) Additionally, there was a positive correlation between the changes in body-specific attention from baseline to 1 month and the changes in the real-world arm use from 1 month to 6 months (r = 0.649, p < 0.01). The blue dots represent individual patients.

Figure 5

Relationship between changes in body-specific attention, real-world arm use, and UL function as revealed by correlation analysis using longitudinal data. There was a significant positive correlation between the amount of change in body-specific attention from baseline to 1 month and the change in real-world arm usage from baseline to 6 months (r = 0.491, p = 0.013). Moreover, there was a significant positive correlation between the amount of change in body-specific attention from baseline to 1 month and the change in real-world arm use from 1 month to 6 months (r = 0.649, p < 0.01). The amount of change in real-world arm use from baseline to 2 months had a significant positive correlation with the amount of change in UL function over the same period (r = 0.40, p = 0.048). In addition, the amount of change in real-world arm use from baseline to 2 months had a significant positive correlation with the amount of change in UL function from baseline to 6 months (r = 0.43, p = 0.034). On the other hand, there was no correlation between body-specific attention and UL function. T: Time of measurement, BL: baseline, M: month, (ex. ΔT_BL-_6M: during the measurement period from baseline to 6 months).