The provided code is a computational model focused on understanding biological mechanisms underlying navigational strategies, specifically investigating the role of different brain areas in spatial navigation using a plus maze task. Here's a breakdown of the biological basis based on the code: ### Biological Context 1. **Navigational Strategies**: - The code examines the use of spatial or **place strategies** in a navigational task. Place strategies typically rely on environmental cues and are assumed to involve the hippocampus, a brain region vital for spatial memory and navigation. 2. **Brain Regions Involved**: - **Hippocampus**: Known to be critical for spatial learning and memory, this region seems to have been manipulated in the study to assess its role in place strategies. The code references "inactivate_HPC," indicating that the hippocampus was inactivated in some experimental conditions. - **Dorsolateral Striatum (DLS)**: Implicated in habit formation and response strategies, its role in place strategies is assessed by potentially inactivating this region ("inactivate_DLS"). 3. **Experimental Manipulations**: - The use of terms like "control," "inactivate_HPC," and "inactivate_DLS" suggests that the model includes experiments where specific regions (hippocampus and DLS) are pharmacologically inactivated using agents like lidocaine while comparing with a control group receiving saline treatments. This is a common method to study the contribution of particular brain areas. 4. **Use of Pharmacological Agents**: - **Lidocaine**: A local anesthetic used here likely to temporarily inactivate specific brain areas (HPC and DLS). It helps in determining the causal role of these regions in implementing place strategies. 5. **Behavioral Task and Outcomes**: - The task appears to be a "plus-maze" task, commonly used to study spatial memory, where subjects (likely rats, as inferred from the dataset reference to "ratdata") must navigate to a goal using spatial cues. - The biological outcome of interest is the percentage of times a certain strategy (place strategy) is utilized under different experimental conditions. These outcomes are compared to understand how inactivating HPC or DLS impacts strategy use. 6. **Data and Model Analysis**: - The code compares experimental data (likely behavioral performance) with model predictions concerning how inactivating specific brain parts affects spatial strategy use. - Results are aggregated over trials, suggesting temporal dynamics and adaptations in strategy use over time. The overarching biological aim reflected in this code is to dissect the specific contributions of the hippocampus and the dorsolateral striatum in executing navigational strategies, using pharmacological inactivations. Such studies provide insights into the neural substrates of learning, memory, and decision-making in spatial contexts.