Abstract
The syndrome of Anosognosia for Hemiplegia (AHP) can provide unique insights into the neurocognitive processes of motor awareness. Yet, prior studies have only explored predominately discreet lesions. Using advanced structural neuroimaging methods in 174 patients with a right-hemisphere stroke, we were able to identify three neural systems that contribute to AHP, when disconnected or directly damaged: the (i) premotor loop (ii) limbic system, and (iii) ventral attentional network. Our results suggest that human motor awareness is contingent on the joint contribution of these three systems.
Highlights
Motor awareness allows individuals to have insight into their motor performance, a fundamental aspect of self-awareness
The regression computed on the lesion sites (Figure 1a) indicated the involvement of grey matter structures previously associated with Anosognosia for Hemiplegia (AHP) (Moro et al, 2016), such as the insula, the temporal pole (t = 4.77; p=0.003), and the striatum (t = 4.68; p=0.003) as well as a very large involvement of white matter (t = 4.98; p=0.002)
Our results suggest a major role of white matter disconnection in AHP that, when combined to the direct grey matter lesions, reveals that AHP is a tripartite disconnection syndrome involving disruptions in tracts and structures belonging to three systems: the pre-motor loop, the limbic system and the ventral attentional network
Summary
Motor awareness allows individuals to have insight into their motor performance, a fundamental aspect of self-awareness. Following brain damage, some patients may fail to acknowledge their contralesional paralysis, even after this has been repeatedly demonstrated to them. This refractory (delusional) unawareness of motor impairments is termed anosognosia for hemiplegia (AHP, Babinski, 1914). The syndrome is usually reported in right hemisphere lesions, in more recent years the possibility of motor awareness deficits following left hemisphere lesions has been advanced (Cocchini et al, 2009). The syndrome is reported to be relatively frequent after right hemisphere damage in the very acute phase after lesion onset (32% rate) but this usually resolves in the first weeks (18% rate within the first week and 5% rate at 6 months; Vocat et al, 2010). Studying AHP offers unique opportunities to explore the neurocognitive mechanisms of motor awareness
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