The code provided is a computational model focusing on the neural circuitry within the basal ganglia (BG), particularly examining the sensitivity analysis of synapses related to dopaminergic input. Understanding this model requires a grasp of the biological components it represents: ### Biological Basis of the Model 1. **Basal Ganglia Circuitry**: - The basal ganglia is a group of subcortical nuclei involved in motor control, action selection, and reinforcement learning. Key components include the **Go** and **No-Go pathways** and the **Subthalamic Nucleus (STN)**, each contributing to the regulation of movement and motor learning. 2. **Dopaminergic Influence**: - Dopamine (DA) plays a crucial role in modulating the activity of the basal ganglia pathways. The code examines the effects of different levels of tonic dopamine input (`Valori_dopamina`), reflecting its role in both excitation and inhibition within the circuitry. - **Go pathway**: Facilitates movement initiation. Dopamine typically excites the Go pathway, reinforcing selected motor commands via the direct pathway. This is represented by the `alpha` parameter in the model. - **No-Go pathway**: Inhibits movement initiation. Dopamine inhibits the No-Go pathway through the indirect pathway, as depicted by the `beta` parameter. - **Cholinergic Interneurons**: Dopamine's interaction with cholinergic interneurons is represented by the `gamma` parameter. These interneurons modulate the activity of both Go and No-Go neurons, affecting overall motor output. 3. **Sensitivity Analysis on Synapses**: - The model conducts a sensitivity analysis on synapses related to the different pathways and nuclei (Go, No-Go, STN). This is achieved by varying synaptic weights (`Wgc`, `Wgs`, `Wnc`, `Wns`) and observing changes in the system's output, which is the **tapping frequency**. - **Tapping Frequency**: The model output `ft` represents the cyclical motor output frequency, measured in cycles per minute. This is a proxy for how the basal ganglia circuitry controls rhythmic motor actions, reflecting the performance of motor tasks. 4. **Synaptic Weights and Modulation**: - Synaptic weights are modulated through percentage changes to reflect how alterations in connectivity or synaptic strength within these pathways influence the basal ganglia's ability to modulate motor outputs. - The model alters weights for sensitivity analysis in two main scenarios: - **Go / No-Go Pathways**: Exploring changes in synapses that impact these pathways' ability to initiate or suppress movements. - **Subthalamic Nucleus (STN)**: STN's role in basal ganglia activity is assessed through changes in synaptic efficacy, reflecting its importance in adjusting motor outputs during high-level motor planning. Together, this model seeks to understand how variations in dopaminergic input and synaptic strength across critical nodes of the basal ganglia can alter motor output, shedding light on the biological underpinnings of motor control and potentially offering insights into disorders like Parkinson's disease.