The code provided is a simulation script for a computational model of the olfactory bulb in the brain, specifically focusing on the interaction between mitral cells (MT) and granule cells (GC). Here's a breakdown of the biological aspects the code is attempting to model: ### Biological Components #### Mitral Cells (MT) - **Role**: Mitral cells are the primary projection neurons of the olfactory bulb, which receive input from the olfactory receptor neurons and transmit the information to various brain regions, including the olfactory cortex. - **Simulation**: The code creates two mitral cell objects (`mt[0]` and `mt[1]`). Each mitral cell receives input via an injected current (`IClamp`), which simulates synaptic input or sensory activation. #### Granule Cells (GC) - **Role**: Granule cells are inhibitory interneurons without axons, which synapse onto the dendrites of mitral cells, providing lateral inhibition and thus sharpening the representation of olfactory information. - **Simulation**: The code constructs two granule cell objects (`gc[0]` and `gc[1]`), which are involved in reciprocal dendrodendritic synapses with the mitral cells. This interaction is crucial for the lateral inhibition mechanism in the olfactory bulb. ### Synaptic Interactions - **Excitatory Synapses**: Each mitral cell connects to a granule cell via excitatory synapses mediated by AMPA and NMDA receptors (`sampa`, `synmt`). These synapses are modeled with specific conductance factors (`synstr`, `nmdafactor`), reflecting their role in excitatory neurotransmission. - **Inhibitory Synapses**: The granule cells provide inhibitory feedback to the mitral cells via synapses (`igp`), controlled by GABAergic neurotransmission, relevant for the inhibitory aspect of the granule cells' function. ### Electrophysiological Parameters - **Resting Potential**: The simulation sets the resting membrane potential (`Vrest = -65 mV`) common for neuronal cells, indicating the baseline state of charge inside the cells relative to outside. - **Temperature**: The simulation considers physiological temperature (`celsius = 35°C`), which influences various kinetic properties of the cells. - **Simulation Time**: The simulation runs for a period specified by `tstop = 2000 ms`, allowing for adequate observation of the dynamic interactions between these cells over time. ### Functional Dynamics - **Network Connections and Event Control**: The code specifies the functional dynamics of the network through `NetCon` objects, which define how action potentials in one neuron can trigger events in another neuron. The weights and delays set in these connections represent the synaptic strength and temporal aspects of these interactions. - **Plasticity Flag**: The script includes a mechanism (`flag`) that seems to toggle the involvement of granule cells in the network, likely used to investigate the effect of granule cell inhibition on mitral cell activity. Overall, this model aims to capture the intricate dynamics within the olfactory bulb, specifically the role of excitatory and inhibitory reciprocal interactions between mitral cells and granule cells, which are crucial for processing olfactory information.