4 Networks and Populations Flashcards
make me less unstable xx
For a quadratic intagrate and fire model, what are the fixed points like? (spiral/node, stable/unstable)
What are the axes for this parabola?
What position are these foxed points on this model’s parabola curve?
-one stable node and one unstable node
-vertical V’ and horizontal V
-stable left and unstable right because of the values of V and model is stable when V is less
What is the equation for the Quadratic Integrate and Fire model?
What are the conditions of this equation?
dV/dt =b + V2
if V=Vpeak then V<-Vreset
Summary of stages in an AP
rmp Na+ closed, K+ closed (inside more neg. than outside)
1depolarisation - Na+ channels open: Na+ influx
(cytosol becomes less neg.)
2repolarisation - Na+ channels inactivating, K+ channels open: K+ efflux
3hyperpolarisation - Na+ channels inactive, K+ channels open
rmp Na+ closed, K+ closed
Which family of channels directly influences itself ?
How does the other type influence the channel?
-ionotropic
-metabotropic controls channels via biochemical G-protein cascade
What are the four steps that preceed and trigger post synaptic potential (PSP)?
1 arrival of presynaptic spike
2 calcium influx causes NT release into synaptic cleft
3 detection of NT molecules by postynaptic receptors
4 binds to and opens NT-gated postsyaltic channels -> ion influx -> changes post synaptic membrane potential
Which is excitatory/inhibitory: glutamate and GABA
glutamate=excitatory
GABA=inhibitory
What do excitaory/inhibitory synapses do to the membrane voltage of the post synaptic neurons?
excitatory: increases Vm /depolarises
inhibitory: decreases Vm /hyperpolarises
What is the IPSC?
What does it represent?
-inhibitory postsynaptic transmembrane current
-current responsible for causing an IPSC
If the synaptic potential Esyn =-75 and the membrane potential of the postsynaptic neuron is -65, what will happen to the membrane potential?
hyperpolarise - decreases Vm
What sort of channel receptors do GABAa and GABAb bind to?
Which ions does each GABA move thru their channels?
GABAa - ionotropic (exclusively Cl-)
GABAb -metabotropic (opens K+ channels)
What is the concentrations of Na+, K+, Cl- ions relative to inside and outside the cell?
K+ higher inside
Na+ lower inside
Cl- higher outside
Why does presynaptic release of GABA (a and b) cause an IPSP?
because both GABA a causes Cl- influx and K+ efflux on postsynaptic neuron thus Vm made more negative
What effect does IPSP have on postsynaptic neuron?
suppresses AP firing
What does the value of tau depend on in the synapse model?
the type of NT used
What type of graph line does a simple model of a synapse use?
decreases exponentially (e-t)
What does the double exponential synapse model allow you to adapt?
What is tau in this model?
-allows you to change the values of tau(decay) and tau(rise)
you can change rise and decay time constant
-time constant (of rise or decay)
As the tau decay (decay time) increases, what happens to the gsyn conductance?
gradient flattens/decreases in the exponentially decreasing line
What are the three synapse models?
-simple
-alpha function
-double exponential
What is Esyn
reversal potential
What is the EPSC?
What is it caused by?
-excitatory postsynaptic transmembrane current
-an increase in membrane voltage of postsynaptic neurons
what are the two type of ionotropic glutamate receptors?
Excitatory or inhibitory?
AMPA, NMDA
excitatory
What receptor channels are present on excitatory neurons?
AMPA gluatamate
NMDA glutamate
What ions are allowed to pass thru AMPA channels?
Na and K
Which is response faster ionotropic or metabotropic?
ionotropic
Which ion blocks NMDA receptor?
How is it removed?
Magnesium
voltage-dependent: depolarisation causes mg2+ to go away
Why must you use double exp. model for GABAb and NMDA receptor currents?
because for each NT, the rise and fall times are not the same
Which NT is suited to which synapse model?
excitatory (glutamate)
AMPA
NMDA
inhibitoty
GABAa
GABAb
AMPA: simple
NMDA: double exp.
GABAa: simple
GABAb: double exp.
What is the difference between temporal summation and spatial summation on postsynaptic neuron?
-temporal: spaced out spiked
-spatial: lots of different presynaptic inputs
How many layers are in the cortex?
six layers
If you want to model a neural network of the cortex, what percentage of excitatory and inhibitory neurons would you use?
Which neuron types in cortex is responsible for excitatory and inhibitory?
80 % excitatory - pyramidial layer 5
20 % inhibitory - interneurons layer 4
What are the conditions of the eqn calculating average population activity of a group of neurons?
○All neurons (N) are identical
○Required same external input current (Iext)
○Interaction strength (wij) is uniform
What is the definition of average population activity of a neural network ?
temporal evolution of population activity in large homogenous neural populations
Does the neural mass model calculate firing rate of neuron?
no calculates the average population activity
What is the equation for leaky integrate and fire model? and the conditions of the model?
dV/dt= b-V
if V=1 then V-> 0
What is the connectivity of the each neuron like when using the leaky integrate and fire to model a neural NETWORK?
each neuron in network: all to all coupling including to itself
What is full connectivity in neural network?
What is random coupling with fixed connection probability “ ?
What is random coupling with fixed number of inputs “ ?
-neurons receive input from all other neurons in the network
-you decide the the probabilty and it changes depending on the N total number of neruons in network to keep probability the same
-you decide number of inputs however this does not change as N changes
