if the connection between a dendritic site and a somatic site is reciprocal, what does that mean for the physical/electrical properties of your typical tapering dendrite?
Bill Connelly wrote:Am I right in thinking that a section of dendrite between points A and B is reciprocal if injection a X pA of current at location A creates Y mV of deflection at location B AND injection of X pas of current at location B creates Y mV of deflection at location A?
And if the connection between a dendritic site and a somatic site is reciprocal, what does that mean for the physical/electrical properties of your typical tapering dendrite?
Keivan wrote:to my knowledge, this is not happening in the CA1 and layer 5 cortical pyramidal neurons in reality.
As I have repeatedly discovered in my career, the informal lunch-seminar approach to science is hard to substitute with formal lectures or the reading of dense scientific papers. Seminars are tailored for an average group of people with the naive assumption that the audience retains all the details and follows and accepts the fundamental logic of the lecturer. In contrast, the essence of lunch conversations is to question the fundamental logic, a quest for clarification and simplification, a search for explanations and answers without a rigid agenda, where the focus is not on covering large chunks of material but on fully understanding even the smallest details.
Dendritic hyperpolarization-activated currents modify the integrative properties of hippocampal CA1 nyramidal neurons
A passive cable structure with current or voltage inputs is a linear system, that is, if you double the input, the output should also double, if you multiply the input by –1, you should get –1 times the output. The response to two stimuli is given by the sum of the responses to the individual stimuli.
Linear scaling tests should always be performed before using electrophysiological data for passive cable modeling, but rarely are.
Conductance inputs however do not behave linearly in a passive system, a fact often forgotten by inexperienced modellers.
If you simulate a synaptic conductance, then double it, you won’t get twice the response, because of a reduced driving voltage, and because of the local increase in net membrane conductance. The responses to very small conductances, however, can scale approximately linearly, if these effects are negligible.
is supported by a large body of data. In addition to the evidence memtioned in my previous post, many papers have shown that excitatory synaptic inputs summate linearly as long as they are subthreshold and are separated sufficiently by time and/or space to not drive membrane potential near threshold or interfere with each other's driving force.except in the near vicinity of spike threshold, neurons are operating in a more or less linear manner
ted wrote:Fairly striking examples of reciprocity are presented in Fig. 9 A and B of Magee, J.C. Dendritic hyperpolarization-activated currents modify the integrative properties of hippocampal CA1 nyramidal neurons J. Neurosci. 18: 7613 - 7624, 1998
Passive systems exhibit a nonintuitive symmetry in voltage responses called reciprocity (see discussion in Major et al., 1993). The voltage response at the soma to current injection at a dendritic location will equal the voltage response at this dendritic location following the same current injection at the soma. It should be noted that the voltage responses at the injection sites and the degree of voltage attenuation between the injection site and the recording site may be drastically different, but the responses at the recording sites will be identical (e.g., figure 1 of Roth and Hausser, 2001). Checking for reciprocity is a good way to determine if a dendritic tree is passive or if blockers have been successful at making it so.
Checking for reciprocity is a good way to determine if a dendritic tree is passive or if blockers have been successful at making it so.
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