Abstract
The behavioral variant of frontotemporal dementia (bvFTD) is related to a variety of social misbehaviors, including criminal behavior (CB) due to deep changes in cognition, behavior, and personality. Recent work suggests that impairment in emotional processing, along with disinhibition, constitutes the necessary elements for CB in bvFTD. However, the underlying neurobiological mechanisms are still unclear. Therefore, we aim at investigating structural and functional brain changes related to CB in bvFTD using magnetic resonance imaging (MRI) with the German Consortium for Frontotemporal Lobar Degeneration (FTLD). Our study comprised 87 patients with bvFTD and 26 healthy controls recruited within different locations of the FTLD Consortium. A subset of 21 patients with bvFTD showed CB, including theft, physical violence, sexual assault, drug abuse, and violations against traffic law. Voxel-based morphometry was performed, generating gray matter density (GMD) images obtained from high-resolution T1-weighted MR images. In addition, surface-based morphometry was performed by reconstruction of cortical thickness using a projection-based thickness approach. Both GMD and cortical thickness were further analyzed in order to detect group differences between bvFTD with and without CB. Resting-state functional MRI was available for a subgroup of 56 patients with bvFTD, including 16 patients showing CB. On a behavioral level, CB in bvFTD was associated with a higher frequency of disinhibition, lower frequency of apathy, and better performance in verbal fluency. Comparing bvFTD with and without CB, we obtained reduced GMD and reduced cortical thickness in the temporal lobe, predominantly in the left hemisphere. Impairment in brain structure was correlated with the Frontal Systems Behavior Scale, particularly with disinhibition, in the left superior temporal gyrus in interaction with CB in bvFTD. Investigating functional MRI data, CB was associated with significant functional brain dysconnectivity, particularly between the left anterior superior temporal gyrus and widely distributed cortical regions, including areas in the vicinity of the precentral sulcus and the inferior frontal junction, related to executive functions. Our study revealed structural and functional brain differences between bvFTD with and without CB, showing CB-related reduced GMD and cortical thickness in the left temporal lobe, indicating disinhibition as the main driver for CB. Interestingly, brain degeneration in the temporal lobe is discussed with CB in bvFTD in the current literature, dominantly affecting the right hemisphere. Our study investigates specifically the neural correlates of CB in bvFTD with MRI, modifying this view. Further work is necessary to shed more light on the role of the temporal lobe in bvFTD with CB.