Network Localization of Awareness in Visual and Motor Anosognosia

Abstract

ObjectiveUnawareness of a deficit, anosognosia, can occur for visual or motor deficits and lends insight into awareness itself; however, lesions associated with anosognosia occur in many different brain locations.MethodsWe analyzed 267 lesion locations associated with either vision loss (with and without awareness) or weakness (with and without awareness). The network of brain regions connected to each lesion location was computed using resting‐state functional connectivity from 1,000 healthy subjects. Both domain specific and cross‐modal associations with awareness were identified.ResultsThe domain‐specific network for visual anosognosia demonstrated connectivity to visual association cortex and posterior cingulate while motor anosognosia was defined by insula, supplementary motor area, and anterior cingulate connectivity. A cross‐modal anosognosia network was defined by connectivity to the hippocampus and precuneus (false discovery rate p < 0.05).InterpretationOur results identify distinct network connections associated with visual and motor anosognosia and a shared, cross‐modal network for awareness of deficits centered on memory‐related brain structures. ANN NEUROL 2023

Convergence of Visual and Motor Awareness in Human Parietal Cortex

“…Accordingly, the functional disconnection map common to both syndromes includes the DAN, involved in topdown control of spatial attention. 35,36 These findings suggest that anosognosia involves both modality-specific mechanisms, as also shown recently by Kletenik et al, 21 as well as attention-related supramodal mechanisms within the DAN.…”

“…This approach was driven by the difficulty of finding bilateral occipital controls. A similar strategy was used in the recent study on the same topic by Kletenik et al 21 Despite these important limitations, we feel that the new link between AS and the neural mechanisms associated with the neglect syndrome, as well as the evidence of a unique combination of modality-specific damage with common convergence on ventral and dorsal frontoparietal mechanisms, significantly advances our understanding of awareness mechanisms in the brain.…”

“…39 However, a recent study highlighted the precuneus as a convergence zone for anosognosia for vision and motor functions. 21 Instead, the convergence within the DAN involved bilateral prefrontal regions that are considered important for consciousness according to other theories. 40 The consistent finding of ventral and dorsal attention regions in severe visual and motor unawareness supports the close connection between attention and consciousness, not only in neurotypical individuals but also in brain-damaged patients.…”

“…The main limitation of this work is that it is based on an indirect analysis of the structural and functional correlates of local damage in both AS and AHP. This indirect "disconnection" approach was specifically developed to study rare syndromes in which it is hard to collect enough cases, 20,21,41 also being recently used to study the neurological correlates of anosognosia. 18,21 In our case, the AS lesions were manually drawn in 2D from pictures of published cases, converted into 3D space inside the MNI space, and compared with 3D lesions derived from MRI scans of occipital stroke patients.…”

“…This procedure is in line with previous studies using lesions drawn from the literature to compute disconnection patterns. 18,[20][21][22][23] For each 3D converted lesion, we calculated the number of voxels, which was used as covariate in subsequent analyses. See Figure 1 for an overview of the analytical strategy.…”