Imagine your brain is like a bustling city, with different neighborhoods dedicated to specific functions. One important neighborhood in this city is the basal ganglia (BG), which controls movement and is involved in motor disorders like Parkinson’s disease. In this study, scientists created a computational model to understand how the structure of the synaptic network in the BG affects the responses of two types of neurons: STN and GPe. By simulating different scenarios and varying the network connections, they discovered that signals from different pathways converge onto the same BG neurons, creating unique response patterns. This finding suggests the existence of functional channels that process information from different body parts simultaneously. Furthermore, neurological disorders like Parkinson’s disease may disrupt the network structure and affect these functional channels, contributing to motor symptoms. This research sheds light on how the organization of synaptic connections in the BG influences the processing of signals from the cortex and provides valuable insights for developing future computational models. To dive deeper into this fascinating study, check out the full article!

IntroductionThe basal ganglia (BG) are involved in motor control and play an essential role in movement disorders such as hemiballismus, dystonia, and Parkinson’s disease. Neurons in the motor part of the BG respond to passive movement or stimulation of different body parts and to stimulation of corresponding cortical regions. Experimental evidence suggests that the BG are organized somatotopically, i.e., specific areas of the body are associated with specific regions in the BG nuclei. Signals related to the same body part that propagate along different pathways converge onto the same BG neurons, leading to characteristic shapes of cortically evoked responses. This suggests the existence of functional channels that allow for the processing of different motor commands or information related to different body parts in parallel. Neurological disorders such as Parkinson’s disease are associated with pathological activity in the BG and impaired synaptic connectivity, together with reorganization of somatotopic maps. One hypothesis is that motor symptoms are, at least partly, caused by an impairment of network structure perturbing the organization of functional channels.MethodsWe developed a computational model of the STN-GPe circuit, a central part of the BG. By removing individual synaptic connections, we analyzed the contribution of signals propagating along different pathways to cortically evoked responses. We studied how evoked responses are affected by systematic changes in the network structure. To quantify the BG’s organization in the form of functional channels, we suggested a two-site stimulation protocol.ResultsOur model reproduced the cortically evoked responses of STN and GPe neurons and the contributions of different pathways suggested by experimental studies. Cortical stimulation evokes spatio-temporal response patterns that are linked to the underlying synaptic network structure. Our two-site stimulation protocol yielded an approximate functional channel width.Discussion/conclusionThe presented results provide insight into the organization of BG synaptic connectivity, which is important for the development of computational models. The synaptic network structure strongly affects the processing of cortical signals and may impact the generation of pathological rhythms. Our work may motivate further experiments to analyze the network structure of BG nuclei and their organization in functional channels.

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