Topological Map of the Body in Post-Stroke Patients: Lesional and Hodological Aspects

Objective: It has been repeatedly hypothesized that at least 3 distinct types of body representations do exist: body schema, a representation derived from multiple sensory and motor inputs; topological map of the body, a structural description of spatial relations among the body parts; and body semantics, a lexical-semantic representation. Although several studies have assessed neural correlates of the topological map of the body in healthy participants, a systematic investigation of neural underpinnings of the topological map of the body in brain-damaged patients is still lacking. Method: Here we investigated the neural substrates of topological map of the body in 23 brain-damaged patients, both from a topological and an hodological perspectives, using Voxel Lesion Symptom Mapping and atlas-based track-wise statistical analysis. Besides neuroimaging investigation, consisting of T1-weighted and FLAIR sequences, patients underwent the frontal body-evocation subtest (FBE) to assess the topological map of the body. Results: The present results reveal a large-scale brain network involved in the topological map of the body assessed with FBE, encompassing both regions of primary elaboration and multisensory associative areas, in the temporal, parietal, frontal, and insular cortices. Hodological analysis revealed significant association between processing of the body topological map and the disconnection of the frontomarginal tract. Conclusions: These findings suggest that the topological map of the body is built up basing on both external and internal information that comes from the body and are constantly updated and integrated. The theoretical and clinical relevance of these results is discussed. General Scientific Summary The present study investigates the neural underpinnings of body representation in stroke patients. Both the topological and hodological approaches show that the knowledge about the spatial features of the body is based on the processing of different bodily information and their multisensory integration. Considering that a deficit in the topological map of the body was identified in patients affected by personal neglect, understanding the nature of such representation could be helpful in better define the clinical features of personal neglect and in designing possible rehabilitation trainings.