The provided code models a point process for deep brain stimulation (DBS) in computational neuroscience. DBS is a neurosurgical procedure used to modulate brain activity, most commonly for the treatment of neurological disorders such as Parkinson's disease, essential tremor, and epilepsy. Here's a breakdown of the biological basis of the code: ### Biological Background **Deep Brain Stimulation (DBS):** - DBS involves the delivery of electrical impulses to specific regions of the brain via implanted electrodes. These impulses can disrupt abnormal neuronal circuits, leading to therapeutic effects. ### Key Biological Components Modeled 1. **Electrode Current (`i`):** - Represents the injected current through the DBS electrode. In the code, positive values indicate depolarizing currents that directly affect the neuronal intracellular environment. This approach reflects the method by which current is applied to stimulate the brain without passing through the cell membrane. 2. **Stimulation Parameters:** - **Amplitude (`amp`):** This reflects the strength of the current delivered by the DBS, which can influence the effective area of stimulation and the extent of neuronal activation. - **Pulse Width (`pw`):** The duration of individual electrical pulses. Modifying pulse width can affect the amount of charge delivered and can influence the types of neuronal elements activated (e.g., axons vs. cell bodies). - **Period:** The time between the beginnings of successive pulses, defined as an inverse of the frequency of stimulation. 3. **Delays and Probabilities:** - **Delay (`del`):** The onset time for the stimulation sequence, allowing synchronization with other elements or phases of a treatment protocol. - **Probability of Activation (`actPrb`):** Represents the stochastic nature of neuronal activation, accounting for the variability in how neurons might respond to each pulse of DBS. 4. **Antidromic and Orthodromic Activation:** - **Antidromic Latency (`adLat`):** The time between stimulation and the observed response in the opposite direction to normal neuronal conduction, highlighting the bidirectional nature of action potential propagation often seen with DBS. - **Orthodromic Event Signaling (`net_event`):** The function of signaling the occurrence of normal directional responses after stimulation. ### Biological Process The model captures key elements of DBS, such as stimulation scheduling, intensity, and probabilistic firing that are important for simulating the effect of DBS on neuronal circuits. The code's logic incorporates probabilistic activation, reflecting inherent biological variability, and models bidirectional action potential propagation, crucial for understanding the complex outcomes of DBS in therapeutic settings. In summary, the code models the initial activation and continued pulse delivery of DBS and its effects on neurons. The parameters allow modulation of the fundamental aspects of DBS, which are crucial in tailoring stimulation protocols for therapeutic purposes.