Evidence of an inferior total-order planning strategy in patients with frontotemporal dementia

Frontotemporal lobar degeneration and social behaviour: Dissociation between the knowledge of its consequences and its conceptual meaning

Inappropriate social behaviour is an early symptom of frontotemporal lobar degeneration (FTLD) in both behavioural variant frontotemporal dementia (bvFTD) and semantic dementia (SD) subtypes. Knowledge of social behaviour is essential for appropriate social conduct. The superior anterior temporal lobe (ATL) has been identified as one key neural component for the conceptual knowledge of social behaviour, but it is unknown whether this is dissociable from knowledge of the consequences of social behaviour. Here, we used a newly-developed test of knowledge about long-term and short-term consequences of social behaviour to investigate its impairment in patients with FTLD relative to a previously-developed test of social conceptual knowledge. We included 19 healthy elderly control participants and 19 consecutive patients with features of bvFTD or SD and defined dissociations as performance differences between tasks for each patient (Bonferroni-corrected p < .05). Knowledge of long-term consequences was selectively impaired relative to short-term consequences in five patients and the reverse dissociation occurred in one patient. Six patients showed a selective impairment of social concepts relative to long-term consequences with the reverse dissociation occurring in one patient. These results corroborate the hypothesis that knowledge of long-term consequences of social behaviour is dissociable from knowledge of short-term consequences, as well as of social conceptual knowledge. Confirming our hypothesis, we found that patients with more marked grey matter (GM) volume loss in frontopolar relative to right superior ATL regions of interest exhibited poorer knowledge of the long-term consequences of social behaviour relative to the knowledge of its conceptual meaning and vice versa (n = 15). These findings support the hypothesis that frontopolar and ATL regions represent distinct aspects of social knowledge. This suggests that rather than being unable to suppress urges to behave inappropriately, FTLD patients often lose the knowledge of what appropriate social behaviour is and can therefore not be expected to behave accordingly.

Language, executive function and social cognition in the diagnosis of frontotemporal dementia syndromes

Frontotemporal dementia (FTD) represents a spectrum of non-Alzheimer's degenerative conditions associated with focal atrophy of the frontal and/or temporal lobes. Frontal and temporal regions of the brain have been shown to be strongly involved in executive function, social cognition and language processing and, thus, deficits in these domains are frequently seen in patients with FTD or may even be hallmarks of a specific FTD subtype (i.e. relatively selective and progressive language impairment in primary progressive aphasia). In this review we have attempted to delineate how language, executive function, and social cognition may contribute to the diagnosis of FTD syndromes, namely the behavioural variant FTD as well as the language variants of FTD including the three subtypes of primary progressive aphasia (PPA): non-fluent/agrammatic, semantic and logopenic. This review also addresses the extent to which deficits in these cognitive areas contribute to the differential diagnosis of FTD versus Alzheimer's disease (AD). Finally, early clinical determinants of pathology are briefly discussed and contemporary challenges to the diagnosis of FTD are presented.

Regional brain atrophy and impaired decision making on the balloon analog risk task in behavioral variant frontotemporal dementia

OBJECTIVE

The goal of this study was 2-fold, first, to compare decision making in behavioral variant frontotemporal dementia (bvFTD) patients and healthy adults using the Balloon Analog Risk Task (BART), and, second, to identify the regions of gray matter atrophy associated with bvFTD patients' BART performance.

BACKGROUND

Stimulus-reinforcement learning is required to evaluate the results of previously chosen actions to improve future decisions. Although there is a well established literature suggesting altered decision making in FTD patients and data from lesion studies suggest orbitofrontal cortex (OFC) involvement in decision making, there is very little research looking at the brain correlates of decision making in FTD populations specifically.

METHOD

Twenty-seven bvFTD patients and 19 age-matched and education-matched normal controls completed the BART. Voxel-based morphometry analysis was performed on the magnetic resonance imaging scans of a subset of patients.

RESULTS

Compared with healthy controls, the bvFTD patients did not learn and pumped less to inflate a balloon to receive a reward, indicating altered stimulus-reinforcement learning. The voxel-based morphometry analysis indicated that bvFTD patients' impaired BART performance was related to atrophy in the right lateral OFC.

CONCLUSIONS

The right lateral OFC is crucial for stimulus-reinforcement learning required for the adjustment of behavior under changing reward contingencies.