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Cortex. 2017 Aug;93:107-118. doi: 10.1016/j.cortex.2017.05.009. Epub 2017 Jun 3.

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

Author information

1
Institute of Psychiatry, Psychology & Neuroscience, Department of Psychological Medicine, King's College London, London, SE5 8AZ, UK; Neuroscience and Aphasia Research Unit, Division of Neuroscience and Experimental Psychology, The University of Manchester, Manchester, UK. Electronic address: roland.zahn@kcl.ac.uk.
2
Neuroscience and Aphasia Research Unit, Division of Neuroscience and Experimental Psychology, The University of Manchester, Manchester, UK.
3
Neuroscience and Aphasia Research Unit, Division of Neuroscience and Experimental Psychology, The University of Manchester, Manchester, UK; Department of Neurology, Washington University School of Medicine, St. Louis, MO, USA.
4
Division of Neuroscience and Experimental Psychology, The University of Manchester, Manchester, UK.
5
Cognitive and Behavioral Neuroscience Unit, D'Or Institute for Research and Education (IDOR), Rio de Janeiro, RJ, Brazil.
6
Neuroscience and Aphasia Research Unit, Division of Neuroscience and Experimental Psychology, The University of Manchester, Manchester, UK; National Hospital for Neurology & Neurosurgery, Queen Square, London, UK.
7
Division of Neuroscience and Experimental Psychology, The University of Manchester, Manchester, UK; Department of Nuclear Medicine and Geriatric Medicine, University Hospital Essen, Germany.
8
Rehabilitation Institute of Chicago, Chicago, IL, USA; Department of Physical Medicine and Rehabilitation, Northwestern University, Chicago, IL, USA.

Abstract

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.

KEYWORDS:

Brodmann Area 10; Disinhibition; Frontal lobe; Impulsivity; Social behaviour

PMID:
28646671
PMCID:
PMC5542070
DOI:
10.1016/j.cortex.2017.05.009
[Indexed for MEDLINE]
Free PMC Article

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