Theory of mind impairment after right-hemisphere damage

Background: Some patients after right-hemisphere damage (RHD) show difficulty in Theory of Mind (TOM), namely, in the ability to attribute and reason about mental states of others and of themselves. Aims: This study explored TOM abilities of individuals with right-hemisphere brain damage. Methods & Procedures: We developed and administered a battery of TOM tasks (the aTOMia battery) to evaluate the TOM abilities of the right-hemisphere brain damaged participants in comparison to healthy control participants. The aTOMia battery included 8 types of TOM tasks. The participants were 25 Hebrew-speakers with RHD aged 25–65 years (mean 53), 8 women and 17 men; 22 of them had a right cerebrovascular accident, and 3 were surgically treated: 2 for tumours, and 1 for cavernoma. Outcomes & Results: The participants with RHD showed heterogeneity with respect to their TOM abilities—17 of them had TOM impairment (aTOMia), whereas 8 showed normal TOM. All patients, including the aTOMic patients, were able to use sentence embedding in their responses to the aTOMia tests items, indicating that their purely syntactic ability of embedding was intact (and did not underlie their aTOMia). Conclusions: Individuals with RHD form a heterogeneous group. Some of them, but not all, have aTOMia. Therefore, the TOM abilities of each individual with right hemisphere should be examined. Whereas purely syntactic abilities are not affected by aTOMia, such TOM impairment may have implications for everyday life, and for the use and comprehension of language during social interaction and in understanding and conveying information.