Neuroimaging studies have described the brain alterations in primary progressive aphasia (PPA) variants (semantic, logopenic, nonfluent/agrammatic). However, few studies combined T1, FDG-PET, and diffusion MRI techniques to study atrophy, hypometabolism, and tract alterations across the three PPA main variants. We therefore explored a large early-stage cohort of semantic, logopenic and nonfluent/agrammatic variants (N = 86) and of 23 matched healthy controls with anatomical MRI (cortical thickness), FDG PET (metabolism) and diffusion MRI (white matter tracts analyses), aiming at identifying cortical and sub-cortical brain alterations, and confronting these alterations across imaging modalities and aphasia variants. In the semantic variant, there was cortical thinning and hypometabolism in anterior temporal cortices, with left-hemisphere predominance, extending toward posterior temporal regions, and affecting tracts projecting to the anterior temporal lobes (inferior longitudinal fasciculus, uncinate fasciculus) and tracts projecting to or running nearby posterior temporal cortices: (superior longitudinal fasciculus, inferior frontal-occipital fasciculus). In the logopenic variant metabolic alterations were more extensive than atrophy affecting mainly the left temporal-parietal junction and extending toward more anterior temporal cortices. Metabolic and tract data were coherent given the alterations of the left superior and inferior longitudinal fasciculus and the left inferior frontal-occipital fasciculus. In the nonfluent/agrammatic variant cortical thinning and hypometabolism were located in the left frontal cortex but Broca's area was only affected on metabolic measures. Metabolic and tract alterations were coherent as reflected by damage to the left uncinate fasciculus connecting with Broca's area. Our findings provide a full-blown statistically robust picture of brain alterations in early-stage variants of primary progressive aphasia which has implications for diagnosis, classification and future therapeutic strategies. They demonstrate that in logopenic and semantic variants patterns of brain damage display a non-negligible overlap in temporal regions whereas they are substantially distinct in the nonfluent/agrammatic variant (frontal regions). These results also indicate that frontal networks (combinatorial syntax/phonology) and temporal networks (lexical/semantic representations) constitute distinct anatomo-functional entities with differential vulnerability to degenerative processes in aphasia variants. Finally, the identification of the specific damage patterns could open an avenue for trans-cranial stimulation approaches by indicating the appropriate target-entry into the damaged language system.

Apathy is frequently reported in Parkinson's disease (PD) patients under subthalamic nucleus deep brain stimulation (STN-DBS). The prevailing clinical view for apathy following STN-DBS is the reduction of dopaminergic medication. However, few clinical reports and recent experimental data suggested the pathogenicity of bilateral STN-DBS on motivation, challenging the leading opinion. Here, we investigate whether bilateralism of STN-DBS influences apathy outcome after STN-DBS, combining pre-clinical and clinical approaches. We assess the motivational effects of chronic unilateral STN-DBS in rats in the exact same conditions having highlighted a loss of motivation under bilateral STN-DBS. Clinical data are obtained by the follow-up of a cohort of parkinsonian patients undergoing unilateral STN-DBS and coming from the clinical center that described apathy related to bilateral STN-DBS itself.Despite an acute effect, which fades rapidly, unilateral STN-DBS did not induce a loss of motivation reminiscent to apathy in rats. In patients, apathy did not increase between the preoperative and the post-operative assessment. Together, those data demonstrate that bilateral but not unilateral STN-DBS can induce a loss of motivation in both rats and patients.This constitutes another evidence of the role of STN-DBS itself for apathy in PD.

No abstract

No abstract

No abstract