Sensorimotor cortex forms prism adaptation memories in older adults and stroke patients

Abstract

Stroke is the largest cause of complex disability in adults. Approximately half of right-hemisphere stroke survivors suffer spatial neglect–an inability to voluntarily orient to people or objects in contralesional space. Neglect is a significant impediment to successful community reintegration. Prism adaptation (PA) is a promising behavioural intervention that can alleviate symptoms of spatial neglect. PA induces a leftward pointing bias–the prism after-effect (AE). In neglect, the prism AE generalises to improve other sensory, motor, and cognitive domains. Although the formation of an AE is a key index in neglect, we do not yet know where it is formed in the brain. Here, we used a novel computational fMRI-based approach to study, for the first time, the brain circuits that mediate the formation of PA in stroke survivors and age matched controls. Healthy individuals (n = 17) and stroke patients (n = 11) performed prism adaptation during fMRI. Temporal signatures of memory formation were extracted from the behavioural data using a state-space model and regressed against the fMRI data. This revealed that, in both groups, fMRI signal in left sensorimotor cortex correlated with the gradual formation of the prism after-effect during adaptation. This indicates that the sensorimotor cortex may be a useful target for neuromodulation that aims to improve the persistence of therapeutic prism after effects.