Cell-Type-Selective Cortical Pathology and Functional Deficits in Synucleinopathy.

Aggregates of α-synuclein (α-syn), a hallmark of synucleinopathies, accumulate in the cerebral cortex accompanied by the emergence of motor symptoms, which are associated with altered cortical neuronal activity. However, the mechanism by which α-syn pathology drives cortical network dysfunction, and how these alterations contribute to impaired motor execution and learning, remain unknown. Here, we adopted a multi-disciplinary approach to elucidate the pathophysiological characteristics in transgenic mice that express mutant human α-syn, with minimal nigrostriatal degeneration. In vivo two-photon imaging revealed distinct alteration patterns in excitatory and parvalbumin (PV)-expressing inhibitory cortical neurons accompanying fine motor deficits during learning. Cell type specific ex vivo whole-cell recording further revealed selectively altered intrinsic properties in excitatory but not PV neurons, consistent with the preferential accumulation of α-syn inclusions in excitatory rather than PV neurons within the same cortical region. These results indicate cell-type selective vulnerability in motor cortex of early stage synucleinopathy, leading to disrupted excitatory/inhibitory balance and dysregulated cortical plasticity, driving early-stage motor symptoms. This study provides evidence for selective vulnerability of excitatory neurons in cortical synucleinopathy.