Task-specific changes in representation and connectivity between parietal and occipito-temporal areas following left hemisphere stroke

Recent studies highlight a critical role of the human lateral occipitotemporal cortex (LOTC) in action understanding, particularly in how we perceive and interpret movements and interactions with tools and bodies. This region, along with connected fronto-parietal areas, has been implicated in limb apraxia, a disorder that affects skilled movement after stroke.

In this study, we focused on whether there were any changes in brain activity or connectivity in areas involving the LOTC and its interconnected perceptuo-motor network after left hemisphere stroke, a common cause of limb apraxia.

We recruited 29 stroke patients and 19 age-matched healthy participants. Using functional neuroimaging, we asked participants to observe static photographs of familiar tools, bodies, non-tool objects, and scrambled images while performing a simple attention task (1-back task). The goal was to map the brain areas specifically involved in tool-related and body-related visual processing. Whole-brain analysis revealed activity changes related to tool and body stimuli in the LOTC and fronto-parietal regions. Interestingly, there were no significant differences in activation between stroke patients and controls based on the overall whole-brain analysis. However, deeper analyses revealed critical group-related differences. Using representational similarity analysis (RSA), we found that stroke patients showed reduced ability to discriminate between tools and non-tools within the right LOTC. Psychophysiological interactions (PPI) analysis further indicated increased connectivity between the left inferior parietal sulcus (IPS) and the left LOTC in stroke patients during tool-related tasks, a finding that correlated with their performance on meaningless imitation apraxia task.

Our findings suggest that limb apraxia after stroke is associated with altered representation of tools and functional connectivity in the perceptuo-motor network, particularly involving parietal and occipitotemporal regions. These results suggest perceptual deficits may be more relevant than previously reported in limb apraxia after stroke.

Highlights

• Consistent activations in the lateral occipitotemporal cortex (LOTC) were identified during tool and body localizer tasks in both stroke patients and healthy controls.

• Representational similarity analysis (RSA) revealed reduced discrimination between tools and non-tools in the right LOTC of stroke patients.

• Differential task-related functional connectivity was observed between the LOTC and intraparietal sulcus (IPS) regions in stroke patients compared to controls during the tools localizer task.

These findings provide insights into altered neural representations and connectivity underlying limb apraxia following left hemisphere stroke.