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Research paper
Atrophy in distinct corticolimbic networks in frontotemporal dementia relates to social impairments measured using the Social Impairment Rating Scale
  1. Kevin C Bickart1,
  2. Michael Brickhouse2,3,
  3. Alyson Negreira2,3,
  4. Daisy Sapolsky3,4,
  5. Lisa Feldman Barrett2,5,
  6. Bradford C Dickerson2,3
  1. 1Department of Anatomy and Neurobiology, Boston University School of Medicine, Boston, Massachusetts, USA
  2. 2Psychiatric Neuroimaging Research Program and Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts, USA
  3. 3Frontotemporal Disorders Unit, Department of Neurology, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts, USA
  4. 4Department of Speech and Language Pathology, Massachusetts General Hospital, Charlestown, Massachusetts, USA
  5. 5Department of Psychology, Northeastern University, Boston, Massachusetts, USA
  1. Correspondence to Dr Brad Dickerson, MGH Frontotemporal Disorders Unit, 149 13th Street, Suite 2691, Charlestown MA 02129, USA; bradd{at}nmr.mgh.harvard.edu

Abstract

Patients with frontotemporal dementia (FTD) often exhibit prominent, early and progressive impairments in social behaviour. We developed the Social Impairment Rating Scale (SIRS), rated by a clinician after a structured interview, which grades the types and severity of social behavioural symptoms in seven domains. In 20 FTD patients, we used the SIRS to study the anatomic basis of social impairments. In support of hypotheses generated from a prior study of healthy adults, we found that the relative magnitude of brain atrophy in three partially dissociable corticolimbic networks anchored in the amygdala predicted the severity of distinct social impairments measured using the SIRS. Patients with the greatest atrophy in a mesolimbic, reward-related (affiliation) network exhibited the most severe socioemotional detachment, whereas patients with the greatest atrophy in an interoceptive, pain-related (aversion) network exhibited the most severe lack of social apprehension. Patients with the greatest atrophy in a perceptual network exhibited the most severe lack of awareness or understanding of others’ social and emotional behaviour. Our findings underscore observations that FTD is associated with heterogeneous social symptoms that can be understood in a refined manner by measuring impairments in component processes subserved by dissociable neural networks. Furthermore, these findings support the validity of the SIRS as an instrument to measure the social symptoms of patients with FTD. Ultimately, we hope it will be useful as a longitudinal outcome measure in natural history studies and in clinical trials of putative interventions to improve social functioning.

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