Impaired Cortico-Amygdala Functional Connectivity Can Drive Social Behavior Deficits in Synucleinopathies

Abstract The small molecule protein α-synuclein forms insoluble aggregates in a group of neurological disorders, including Parkinson’s disease and dementia with Lewy bodies (DLB), which are collectively called synucleinopathies. In PD and DLB, the amygdala has been identified as a particularly susceptible region in the brain for the deposition of Lewy-like α-synuclein aggregates. Though α-synuclein aggregation is closely associated with neurodegeneration, there is a poor correlation between neurodegeneration in the amygdala and the clinical features of PD/DLB. We hypothesize that, prior to neurodegeneration, α-synuclein aggregation disrupts functional cortical modulation of the amygdala circuits, leading to emotion dysregulation in synucleinopathies. In the present study, we combined electrophysiology, optogenetics, mouse model of synucleinopathies, and behavioral analysis to test this hypothesis. Using an α-synuclein preformed fibrils (PFFs)-based mouse model of synucleinopathies, we reported dynamic changes in the levels of α-synuclein pathology in the basolateral amygdala (BLA). Such dynamic changes of pathology associated with a decreased cortico-BLA connection strength prior to a significant loss of cortical axon terminals. In parallel to the reduced cortico-BLA connection, PFFs-injected mice manifested impaired social preference behavior. The impaired sociability of PFFs-injected mice could be rescued by chemogenetic stimulation of cortico-BLA inputs. Altogether, we presented a series of evidence to delineate key circuit events associated with α-synuclein pathology development in the amygdala circuits. The present work highlights the necessity of a thorough investigation of functional consequences of α-synuclein aggregation to advance our understand of pathophysiology of synucleinopathies and development of effective therapies.