The provided code models a neural network within the olfactory bulb, specifically focusing on the olfactory sensory neuron (OSN) input to mitral cells and their interaction with peri-glomerular cells (PG cells). The goal is to simulate the neural processing that occurs in the olfactory bulb, which is the first site of synaptic processing of olfactory information. ### Biological Elements Modeled: 1. **Olfactory Sensory Neurons (OSNs)**: - The OSNs are represented as sources of stimulation to the mitral and PG cells. These neurons would ordinarily detect odorant molecules binding to receptors in the nasal cavity and transmit this information to the olfactory bulb. - In the code, OSNs are modeled using `ThetaStim` objects that simulate periodic inputs, perhaps mimicking rhythmic breathing. 2. **Mitral Cells**: - Mitral cells are the principal neurons of the olfactory bulb responsible for receiving input from OSNs and transmitting processed information to higher brain areas. - The model includes a single mitral cell (`m1`) which receives excitatory input from OSNs through glutamatergic synapses (`ApmdaNmda`) to mimic the real synaptic connections where glutamate is the main neurotransmitter. 3. **Peri-glomerular Cells (PG Cells)**: - PG cells are interneurons in the olfactory bulb that modulate the input to mitral cells, typically through inhibitory connections. - In this model, the PG cell receives excitatory input from OSNs and provides reciprocal inhibitory feedback to the mitral cell. The inhibition in the model uses a `FastInhib` synapse setup, reflecting GABAergic inhibition as observed in biological systems. 4. **Synaptic Interactions**: - The model incorporates key synaptic interactions: excitatory glutamatergic inputs to both mitral and PG cells, and inhibitory interactions where PG cells inhibit mitral cell dendrites. - This mimics the balance of excitation and inhibition that regulates sensory processing and enhances the contrast and discrimination of olfactory signals. 5. **Plasticity**: - The mention in the code about turning off plasticity suggests interest in modeling stable synaptic interactions without adaptive changes. This could represent an effort to understand baseline neural dynamics without learning or synaptic strengthening effects. 6. **External Inputs - Light Stimulation**: - There are also "Light" inputs, similar to OSNs. These might represent another form of sensory input or experimental manipulation used to probe or modulate network dynamics further. ### Key Modeling Objectives: - **Connectivity**: The model sets up neural circuits similar to those found in the olfactory bulb that establish typical patterns of excitation and inhibition between neurons to study their function. - **Temporal Patterns**: By using `ThetaStim`, the model can simulate temporal patterns akin to breathing cycles, which are relevant because olfactory processing is often tied to respiratory rhythms. - **Gating and Control**: The use of various control panels and weight adjustments implies a focus on experiment-like manipulations, allowing researchers to explore how changes in synaptic weights or stimulation patterns impact the processing of sensory inputs. ### Conclusion: This code aims to simulate an essential component of olfactory processing, specifically how the first stages of olfactory information are modulated and transmitted within the olfactory bulb neural circuits. By modeling the interactions between key neurons using synaptic mechanisms and temporal stimulations, researchers can investigate how sensory information is encoded and processed before reaching other brain areas associated with smell perception.