# 8.6 Mathematical models of hippocampal spatial memory  (Page 11/13)

 Page 11 / 13

We also analyze multiplicative STDP as an improved variation of STDP. We display the forward and backward synaptic weights as a function of lap in [link] .

We observe an asymptotic trend of the weight changes in this regime as opposed to the stepwise form of weight changes in regular, additive STDP. We also depict the place field backward shift in [link] .

When using multiplicative STDP, we see a faster backward shift in earlier laps due to the faster initial increase in synaptic weight. This shift also slows down significantly in later laps due to the slowed increase in weights, leading to final place field stabilization. This trend appears to agree with the nature of the backward shift in experimental results [link] . While this is a slightly improved fit to experimental data as opposed to STDP, the weight bounds are directly incorporated into the weight modification equations, making it a better approximation of results than an explanation of the mechanisms behind synaptic plasticity.

Having explained the advantages and disadvantages of STDP, we now look at CaDP and compare its simulation results with STDP. First, we will depict the changes in calcium concentrations in different synapses to better illustrate the mechanisms behind CaDP.

The plot above shows calcium changes in the forward connection from cell 1 to cell 2 and the two counterclockwise connections associated with cell 1. We observe that the clockwise synapse reaches a calcium level above the LTP threshold due to effective pre-post firing. We also notice that presynaptic firing without postsynaptic response results in LTD calcium levels. Also notice that the initial increase in calcium concentration from baseline levels results from the peak in the $f$ function as a result from presynaptic spiking, and the subsequent increases of calcium into the LTP region are a result from postsynaptic feedback from the back-propagating action potential. Furthermore, persistent postsynaptic cell firing following presynaptic stimulus causes a sustained LTP calcium concentration and allows for increased potentiation of synaptic weights.

The changes in calcium levels yield the following weight changes and backward shift over the simulation as depicted below in [link] .

These plots show that CaDP is able to reproduce the same weight changes and backward shift found in STDP. However, there are a couple of slight differences. The weight changes in STDP result only following the occurence of a postsynaptic spike. However, in CaDP, weights are constantly being changed as a function of calcium levels. Furthermore, we note that the depression of the backward connections occurs in an almost entirely different manner than in STDP: in STDP, LTD was an inherent part of the learning rule whenever a postsynaptic spike preceded a presynaptic spike. In CaDP, LTD results from the absence of or extended time between the postsynaptic spike following presynaptic stimulation. As such, the second LTD window is an essential consequence of the CaDP model in the depression of synaptic weights.

where we get a research paper on Nano chemistry....?
what are the products of Nano chemistry?
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
learn
da
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Bhagvanji
Preparation and Applications of Nanomaterial for Drug Delivery
revolt
da
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
I only see partial conversation and what's the question here!
what about nanotechnology for water purification
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
Nasa has use it in the 60's, copper as water purification in the moon travel.
Alexandre
nanocopper obvius
Alexandre
what is the stm
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
what is Nano technology ?
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
why we need to study biomolecules, molecular biology in nanotechnology?
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
why?
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
how did you get the value of 2000N.What calculations are needed to arrive at it
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