Analyzing theory of mind impairment in patients with behavioral variant frontotemporal dementia.

OBJECTIVE

Behavioral variant frontotemporal dementia (bvFTD) and theory of mind (ToM) have common neuroanatomical aspects. This pilot study analyzed the qualitative features of ToM relatively to the site of prefrontal atrophy, aiming to identify a neurobehavioral pattern of bvFTD.

METHOD

Fourteen bvFTD patients were compared with 14 healthy subjects with similar age, years of schooling, gender distribution, and social background. The faux pas task (FPT) measured the recognition and comprehension of faux pas (FP) and awareness of the factual details on 20 stories. Magnetic resonance assessed prefrontal atrophy.

RESULTS

The bvFTD patients were significantly impaired in FP recognition and comprehension and in attribution of non-existent FP. Qualitative analysis revealed five types of errors: misidentification of characters, misidentification of emotions, excessive cohesiveness to the factual context, delusional interpretations, and non-responses. The FPT recognition and comprehension scores were unrelated to story factual details or other neuropsychological performance. Conversely, the FP comprehension scores related to disease duration, the delusional errors to disease duration and prefrontal orbital atrophy, and the cohesiveness errors to age and prefrontal dorsolateral atrophy.

CONCLUSIONS

In bvFTD, ToM is characterized by misinterpretation of mental states and concrete thinking, which is related to disease severity and distinct areas of prefrontal atrophy. This neurobehavioral pattern may be a marker for bvFDT.