The provided code is part of a computational model focusing on simulating and analyzing neuronal activity in specific brain regions linked to the basal ganglia. Here is an overview of the biological basis of the model: ### Biological Basis #### Basal Ganglia Structure and Function The code models several key components of the basal ganglia, a group of nuclei in the brain involved in motor control, cognitive functions, and learning processes. The structures included in the model are: - **Striatum (D1 and D2):** The striatum is divided into two subpopulations of medium spiny neurons that possess distinct dopamine receptor types: - **D1-type** receptors are primarily involved in the direct pathway, facilitating movement. - **D2-type** receptors are part of the indirect pathway, which inhibits movement. - **Subthalamic Nucleus (STN):** This structure plays a crucial role in the indirect pathway. It acts as an excitatory input to the globus pallidus and substantia nigra, modulating movement by exciting the inhibitory output structures of the basal ganglia. - **Globus Pallidus (External - GPe):** Engages in the indirect pathway by inhibiting the subthalamic nucleus and consequently modulates the activity of the thalamus and cortex. - **Globus Pallidus (Internal - GPi):** Acts as the main output nucleus of the basal ganglia, providing inhibitory signals to the thalamus, thereby regulating motor control and movement execution. #### Neuronal Dynamics and Network Activity The model captures the dynamics of these components by analyzing spike trains and raster plots of simulated neuronal activity. The structured raster plots illustrate how input spikes, presumably from sensory or cortical sources, propagate through the network, affecting various basal ganglia nuclei. - **Input Streams and Network Events:** The model simulates input streams (`n_in`, `t_in`) and network events (`out_n`, `t_out`), analyzing how these affect each nucleus. The mapped temporal dynamics (`dt`) simulate how different neurons within each nucleus respond over time, illustrating their collective influence on basal ganglia output functions. - **Nucleus-Specific Activity:** By plotting activity specific to the D1 and D2 subtypes of the striatum, STN, GPe, and GPi, the model sheds light on their roles and interactions. Each subplot displays the temporal firing patterns associated with the respective population of neurons. In essence, this model helps elucidate the dynamical properties and interactions within the basal ganglia circuitry, which are crucial in understanding the regulation of voluntary movements and pathologies like Parkinson's disease. It enables exploration of how disruptions in neural activity and pathway imbalances can lead to motor control disorders.