Anosognosia for Hemiplegia as a tripartite disconnection syndrome

Abstract

1The rare syndrome of Anosognosia for Hemiplegia (AHP) can provide unique insights into 2 the neurocognitive processes of motor awareness. Yet, prior studies have only explored 3 predominately discreet lesions. Using advanced structural neuroimaging methods in 174 patients with 4 a right-hemisphere stroke, we were able to identify three neural networks that contribute to AHP, 5 when disconnected: the (1) premotor loop (2) limbic system, and (3) ventral attention network. Our 6 results suggest that human motor awareness is contingent on the joint contribution of these three 7 systems. 83 Motor awareness allows individuals to have insight into their motor performance, a 9 fundamental aspect of self-awareness. However, following damage to the right hemisphere, patients 10 with left paralysis may show delusions of intact motor ability, or anosognosia for hemiplegia (AHP, 11 1). Hence, studying AHP offers unique opportunities to explore the neurocognitive mechanisms of 12 motor awareness. 13While early studies regarded AHP as secondary to concomitant spatial deficits such as hemineglect 14 2 caused by parietal lesions, more recent experimental and voxel-based, lesion-symptom mapping 15 (VLSM) results suggest that AHP is an independent syndrome. These earlier studies address AHP as 16 an impairment of action and body monitoring, with lesions to the lateral premotor cortex and the 17 anterior insula (3,4), affecting patients' ability to detect discrepancies between feed-forward motor 18 predictions and sensorimotor feedback. However, these hypotheses are insufficient to explain all the 19 AHP symptoms, such as patients' inability to update their beliefs based on social feedback or more 20 general difficulties experienced in their daily living (5,6). Indeed, others have suggested that AHP 21 can be caused by a functional disconnection between regions processing top-down beliefs about the 22

Welcoming back my arm: Affective touch increases body ownership following right hemisphere stroke

“…However, our exploratory VLSM using less restrictive criteria revealed that lesions in the insula and corpus callosum, and, resulted in significantly less increase in body ownership following other-affective touch. These findings are consistent with the proposed role of the insula in body awareness, as well as the importance of white matter tracts in self-awareness (Pacella et al, 2019) and body ownership (Moro et al, 2016;Martinaud et al, 2017) and warrant further study.…”

White matter variability, cognition, and disorders: a systematic review

“…the 'third variable problem'). While this question is beyond the scope of the current study, ideally, future research could explore another statistical framework to assess causal relationships between the variables (Pacella et al, 2019).…”

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