In Parkinson's disease, global social maladjustment and anxiety are frequent after subthalamic nucleus (STN) stimulation and are generally considered to be linked with sociofamilial alterations induced by the motor effects of stimulation. We hypothesized that the STN is per se involved in these changes and aimed to explore the role of STN in social and anxogenic-like behaviors using an animal model.
Nineteen male Wistar rats with bilateral lesions of the STN were compared with 26 sham-lesioned rats by synchronizing an ethological approach based upon direct observation of social behaviors and a standardized approach, the elevated plus maze (EPM). Comparisons between groups were performed by a Mann–Whitney–Wilcoxon test.
Lesioned rats showed impairments in their social (P = 0.05) and aggressive behaviors with a diminution of attacking (P = 0.04) and chasing (P = 0.06). In the EPM, concerning the open arms, the percentage of distance, time, inactive time, and entry were significantly decreased in lesioned rats (P = 0.02, P = 0.01, P = 0.04, and P = 0.05). The time spent in non-protected head dips was also diminished in the lesioned rats (P = 0.01).
These results strongly implicate the STN in social behavior and anxogenic-like behavior. In human, as DBS induces changes in the underlying dynamics of the stimulated brain networks, it could create an abnormal brain state in which anxiety and social behavior are altered. These results highlight another level of complexity of the behavioral changes after stimulation.