# Biological Basis of the DetAMPANMDA Model The provided code models synaptic transmission involving AMPA and NMDA receptors, taking into account presynaptic short-term plasticity. These elements are crucial for understanding synaptic dynamics and their role in learning, memory, and neural computation. ## Key Biological Components ### AMPA and NMDA Receptors - **AMPA Receptors**: These are ionotropic receptors that mediate fast synaptic transmission in the central nervous system. The model uses a dual-exponential conductance profile for AMPA receptors, governed by rise (`tau_r_AMPA`) and decay (`tau_d_AMPA`) time constants, reflecting the rapid kinetics of AMPA receptor-mediated currents. - **NMDA Receptors**: These receptors exhibit both voltage-dependent and ligand-gated properties. They play a critical role in synaptic plasticity due to their permeability to calcium ions, which trigger various intracellular signaling pathways. The NMDA component also follows a dual-exponential profile, with its kinetics defined by `tau_r_NMDA` and `tau_d_NMDA`. ### Magnesium Block NMDA receptor activity is modulated by extracellular magnesium (`mg`), which blocks the receptor at resting potential. The code incorporates this phenomenon with the `mggate` variable, calculated using a function that models the voltage-dependent block described by Jahr & Stevens (1990). ### Synaptic Plasticity The model integrates presynaptic short-term plasticity mechanisms, drawing from Fuhrmann et al. (2002): - **Facilitation (`Fac`)**: A process where synaptic strength temporarily increases due to the residual calcium effect, which elevates neurotransmitter release probability. - **Depression (`Dep`)**: A decrease in synaptic strength due to the depletion of readily releasable vesicles. - **Utilization of Synaptic Efficacy (`Use`)**: Describes the initial probability of vesicle release during synaptic transmission. ### Synaptic Conductances and Current The model computes the conductance changes and resultant synaptic currents (`i_AMPA` and `i_NMDA`) for both receptor types. The postsynaptic current (`i`) is a sum of the AMPA and NMDA components, modulated by their respective conductances (`g_AMPA`, `g_NMDA`) and driving forces (difference between membrane potential `v` and reversal potential `e`). ### Synaptic Weight Modification The code accounts for synaptic efficacy through variables like `weight_AMPA` and `weight_NMDA`, adjusted for facilitation and depression effects at each synaptic event. The time and strength of neurotransmitter release are updated using dynamic factors (`factor_AMPA`, `factor_NMDA`) to simulate realistic synaptic transmission. ## Conclusion The model captures essential dynamics of synaptic transmission involving AMPA and NMDA receptors with an emphasis on the temporal characteristics of receptor activation and the probabilistic nature of neurotransmitter release. These features are integral to representing synaptic behavior under various physiological and pathophysiological conditions, providing insights into processes such as learning and memory in neural networks.