From 1719c5e3737252d8cf8cc80fb4012a355b99ef3b Mon Sep 17 00:00:00 2001 From: ocrampal Date: Mon, 6 Apr 2026 11:25:11 +0200 Subject: [PATCH] fix --- neuron/BEH-BD.md | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) diff --git a/neuron/BEH-BD.md b/neuron/BEH-BD.md index bd3d17b..df24b9b 100644 --- a/neuron/BEH-BD.md +++ b/neuron/BEH-BD.md @@ -10,7 +10,7 @@ Qui comprendiamo: The dendrite is the receiving arm of a neuron — a long, branching extension of the cell body whose job is to collect the electrical signals generated by postsynaptic spines, integrate them in space and time, and route their combined effect toward the soma, where the decision to fire an action potential is made. A single dendritic branch can be thought of as a shared electrical highway: dozens to hundreds of postsynaptic spines line its length, each one a private compartment where synaptic signals are first detected, and the dendrite shaft is the common conductor that carries all of their contributions forward. -Each spine sits along the branch and generates a small electrical signal — an excitatory postsynaptic potential, or EPSP — whenever its AMPA receptors are activated by neurotransmitters from the presynapse. This EPSP spreads from the spine head through the narrow spine neck and into the dendrite shaft, where it joins a shared pool of electrical activity. The spine neck is not a neutral conduit — it has electrical resistance that attenuates and slows the signal as it passes through, and its geometry can change with synaptic activity. A wider, shorter neck passes the EPSP more faithfully; a narrower, longer neck attenuates it more severely. This geometry is one of the mechanisms through which plasticity expresses itself physically: LTP widens the neck, making a strengthened synapse electrically closer to the dendrite. +Each spine sits along the branch and generates a small electrical signal — an excitatory postsynaptic potential, or EPSP — whenever its AMPA and NDMA receptors are activated by neurotransmitters from the presynapse. This EPSP spreads from the spine head through the narrow spine neck and into the dendrite shaft, where it joins a shared pool of electrical activity. The spine neck is not a neutral conduit — it has electrical resistance that attenuates and slows the signal as it passes through, and its geometry can change with synaptic activity. A wider, shorter neck passes the EPSP more faithfully; a narrower, longer neck attenuates it more severely. This geometry is one of the mechanisms through which plasticity expresses itself physically: LTP widens the neck, making a strengthened synapse electrically closer to the dendrite. Once in the shaft, EPSPs from different spines summate. If two spines fire close together in time, their EPSPs overlap and their combined depolarisation is larger than either alone — this is temporal summation. If two spines fire simultaneously but are located close together along the branch, their EPSPs also overlap in space before they decay — this is spatial summation. The dendrite is therefore performing a continuous integration across both time and space, weighting each spine's contribution by how recently it fired and how well its signal survived the journey through the neck and along the shaft. @@ -37,7 +37,6 @@ In this model we decide to simplify: - We do not model active dendritic conductances — the shaft is a passive cable with no dendritic spikes - We do not model bAP distance attenuation — all spines receive the bAP at full amplitude regardless of their position - We do not model structural plasticity — spine neck widening and retraction are not implemented -- The soma firing decision is external — V_dend is computed but the threshold crossing is driven by an external `soma_spike_train` The simplifications imply that: @@ -45,7 +44,6 @@ The simplifications imply that: - Removing active conductances means the dendrite cannot generate dendritic spikes. Summation is strictly linear — two spines together produce exactly twice the V_dend of one spine alone. There is no threshold event within the dendrite itself, only at the soma. - Removing bAP attenuation means all spines have equal access to the coincidence signal regardless of distance from the soma. Proximal and distal synapses have identical plasticity thresholds. The functional gradient that makes dendritic location matter is absent. - Removing structural plasticity means the geometry of the dendrite is fixed. LTP and LTD change AMPA receptor density at each spine but do not change how well those spines couple electrically to the dendrite. The structural component of long-term potentiation — which in biology is arguably more important than the receptor component for sustained changes — is not captured. -- Making soma firing external means V_dend is computed but does not itself trigger anything. The soma threshold decision is provided by `soma_spike_train` rather than emerging from the model. This preserves the bAP mechanism without requiring an explicit integrate-and-fire soma model. The only behavior we model: