خیالپردازی درباره غیر ممکن: بازنمایی حرکتی در ناتوانی در ادراک بیماری برای همی پلژی

Abstract Anosognosia for hemiplegia (AHP) is characterised by poor insight or underestimation of hemiplegia after brain injury. Recent explanations of AHP have used an established ‘forward model’, which proposes that normal motor awareness involves comparing the predicted and actual sensory consequences of movements. These accounts propose that AHP patients may be able to form representations of their intended movements (i.e., motor representations), but fail to register discrepancy between intended and actual movements. A prediction arising from this proposal is that AHP patients are able to generate motor representations involving their hemiplegic limb(s). Our study provides the first direct examination of this prediction in patients with AHP. We used an existing ‘grip selection task’, which investigates motor representations by comparing how patients would grasp an object and how they actually grasp the same object. Eight right hemisphere stroke patients with AHP, 10 control patients (non-AHP), and 22 age-matched healthy volunteers (HVs) completed the task. Results showed that HVs outperformed both AHP and non-AHP patients in their motor representations for the hemiplegic limb; however, the performance of AHP and non-AHP patients did not differ significantly. Motor representations for the intact limb were lower than normal in AHP patients, whereas performance in non-AHP patients was midway between the AHP and HV groups. Findings suggested that the ability to form motor representations lie on a continuum, but that impaired motor representations for the paralysed limb cannot account for AHP. Distorted motor representations, in combination with other deficits, might contribute to the pathogenesis of AHP

2. Results Each group's AHP assessments, gender, age, MRC muscle power, MMSE, and NART score are summarised in Table 1. Eight patients fulfilled the criteria for AHP (4 males, 4 females) and AHP was absent in 10 control/non-AHP patients (8 males, 2 females). The proportion of males and females in each group did not differ (all ps > .10). The three groups were matched for age (p = .893), and both patient groups were matched in terms of the degree of hemiparesis (p = .282), length of time between stroke and participation in the study (p = .915), pre-morbid intelligence (p = .432), and current cognitive function (p = .310). However, compared with HVs, both AHP and non-AHP patients had significantly lower pre-morbid intelligence (p < .001 and .002 respectively) and current cognitive functioning (p < .001 and .008 respectively). Table 1. Summary of participant characteristics, AHP assessments, and grip selection task results. AHP patients (n = 8) Non-AHP patients (n = 10) HVs (n = 22) Gender (% male) 50.00a 80.00a 45.45a Age 65.50 (32.00)a 68.50 (34.00)a 68.50 (25.00)a Time since insult 8.00 (36.00)a 7.00 (77.00)a – MRC muscle power scorea 0.00 (2.00)a 0.50 (2.00)a – MMSE 24.00 (8.00)a 26.00 (7.00)a 29.00 (3.00)b NARTb 101.00 (29.00)a 103.00 (10.00)a 113.00 (31.00)b Verbal awareness scores Upper limb 1 (2) 0 (0) – Lower limb 1 (2) 0 (0) – Potential ability scores Monomanual actions 7 (8) 0 (2) – Bimanual actions 7 (6) 2 (4) – Locomotor actions 3 (10) 0 (3) – Grip selection task Left MI accuracy 79.69 (43.75)a 84.38 (71.88)a 92.19 (21.88)b Right MI accuracy 65.60 (53.10)a 84.40 (43.75)b 93.75 (31.25)b Note. Figures are group median (range) unless otherwise stated. Dashes indicate measure is not applicable. AHP = anosognosia for hemiplegia; non-AHP = non-anosognosia for hemiplegia; HVs = healthy volunteers. MRC = Medical Research Council; MMSE = Mini Mental Status Examination; NART = National Adult Reading Test. Different letters in the same row indicate significant differences between groups. a One AHP and two non-AHP patients did not complete this assessment. b One AHP and one non-AHP patient did not complete this assessment. Table options 2.1. Congruence between motor imagery and motor control Table 1 shows participants’ congruence scores for the left (hemiplegic) and right (intact) arm. The omnibus test of left MI accuracy scores showed that AHP patients had significantly lower congruence between MI and MC conditions than HVs, H(2) = 10.09, p = .006, and post hoc analyses showed that non-AHP patients were similarly impaired relative to HVs, U = 55.50, p = .049. There was no difference in the left MI accuracy of AHP and non-AHP patients (p > .10). Analysis of right MI accuracy scores revealed significantly lower congruence between MI and MC in AHP patients compared with HVs, H(2) = 13.32, p = .001. There were no other significant differences in MI accuracy between groups (all ps > .10). Finally, because NART and MMSE scores were significantly lower in both patient groups compared with HVs, the possible influence of these factors on MI accuracy was explored post hoc using Spearman's correlations. All correlations were non-significant (all ps > .05); however, there was a marginal correlation between MMSE score and left MI accuracy (rs = .30, p = .054).