Visuospatial deficits after stroke: Towards better classification, diagnostics, and rehabilitation.

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Project Summary Non-primary visuospatial deficits are common after right-hemisphere (RH) injury, and they are known predictors of long-term disability after stroke. However, compared to impairments of language and motor function, they are less obvious and receive less attention in stroke research, diagnostics, and rehabilitation, resulting in underdiagnosis and undertreatment of RH stroke. Part of the problem is that these deficits and their neural bases are poorly understood, not least because of the heterogeneity of the tests used to assess them and a lack of agreement on their definition, which hamper comparison across studies. Based on our preliminary data and a review of the literature, we posit that these deficits, which are often subsumed under “spatial neglect”, reflect four core factors: lateralized perceptual-attentional, lateralized motor- intentional, non-lateralized attentional, and constructional. We further posit that they can be dissociated with appropriate assessments, are associated with different lesion sites, and respond to different treatments. To pave the way for better assessments and effective individualized treatments, the proposed research seeks to identify the core factors underlying visuospatial deficits, the assessments most sensitive and specific to them, their associations with functional outcomes after stroke, and their neural bases. SA1: Identify core visuospatial deficits and tests that are sensitive and specific to them and determine their association with long-term stroke outcomes. Assess long-term survivors of RH vs. LH stroke and matched Controls with a comprehensive battery of visuospatial tests. Use factor analysis to confirm that performance is better described by a model assuming multiple different rather than one unitary underlying deficit. Demonstrate that core deficits (captured as composite scores across battery subtests) are more severe in RH than LH stroke, and determine which best predict functional ability and self-reported quality of life. SA2: Identify neural bases of visuospatial deficits and their recovery. Acquire functional and anatomical magnetic resonance imaging (MRI) data from MRI-eligible participants of SA1. Using novel lesion-symptom and functional-anomaly mapping methods, test hypotheses regarding associations between specific lesion locations and deficits. Confirm that, in analogy to findings from aphasia research, stroke survivors with visuospatial deficits show increased contralesional task-evoked activation, and that it relates to performance. In addition to identifying the fundamental and dissociable components of visuospatial ability and their neural basis, the results will allow us to (1) improve RH stroke diagnostics of by identifying tests that are highly sensitive and specific to RH stroke, (2) provide more accurate outcome prognoses based on test results and lesion characteristics, and (3) customize rehabilitation based a patient’s visuospatial profile. They will also lay the basis for clinical trials evaluating noninvasive neurostimulation (rTMS, tDCS) for boosting rehabilitation of visuospatial deficits by modulating contralesional brain activation.