presented by suganya karunakaran
DESCRIPTION
Reduction of Spike Afterdepolarization by Increased Leak Conductance Alters Interspike Interval Variability. Fernando R. Fernandez and John A.White The Journal of Neuroscience, January 28, 2009 • 29(4):973–986 • 973. Presented by Suganya Karunakaran. Spike Afterdepolarization. - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: Presented by Suganya Karunakaran](https://reader034.vdocuments.mx/reader034/viewer/2022051622/56814ef8550346895dbc8aef/html5/thumbnails/1.jpg)
Presented by Suganya Karunakaran
Reduction of Spike Afterdepolarization by Increased Leak Conductance Alters Interspike Interval Variability
Fernando R. Fernandez and John A.WhiteThe Journal of Neuroscience, January 28, 2009 • 29(4):973–986 • 973
![Page 2: Presented by Suganya Karunakaran](https://reader034.vdocuments.mx/reader034/viewer/2022051622/56814ef8550346895dbc8aef/html5/thumbnails/2.jpg)
Spike Afterdepolarization
Membrane potential depolarization that follows an action potential
May occur before (early) or after (delayed) full repolarization
Common in cardiac muscles Sometimes occurs in tissues not
normally excitable
![Page 3: Presented by Suganya Karunakaran](https://reader034.vdocuments.mx/reader034/viewer/2022051622/56814ef8550346895dbc8aef/html5/thumbnails/3.jpg)
Leak Conductance
Leak conductance is generated by membrane damage surrounding an electrode and an increase in K+ permeability evoked by cytosolic elevations of Sodium and Calcium
![Page 4: Presented by Suganya Karunakaran](https://reader034.vdocuments.mx/reader034/viewer/2022051622/56814ef8550346895dbc8aef/html5/thumbnails/4.jpg)
Interspike Interval Variability Inter-spike Interval Variability of neuronal spike train –
important indicator of the type of processing a neuron performs on its synaptic inputs
Simplest measure – Coefficient of Variability
CV = standard deviation of ISI distribution/mean ISI Refractory period lowers the CV at high
firing rates when it tends to force regularity in the ISI duration
![Page 5: Presented by Suganya Karunakaran](https://reader034.vdocuments.mx/reader034/viewer/2022051622/56814ef8550346895dbc8aef/html5/thumbnails/5.jpg)
High-Conductance state
State of neurons in an active network Total synaptic conductance received by
the neuron (over a period of time) is larger than its resting conductance
Found in thalamocortical system especially cerebral cortex
Neurons can integrate differently in this state
Can be reproduced by dynamic-clamp experiments
![Page 6: Presented by Suganya Karunakaran](https://reader034.vdocuments.mx/reader034/viewer/2022051622/56814ef8550346895dbc8aef/html5/thumbnails/6.jpg)
Computational Consequence Neuronal responses in high-conductance
states are probabilistic because of the high variability of responses due to the presence of fluctuating background activity
Change the response properties of neurons
Red- deterministic neuron
Green- probabilistic neuron
![Page 7: Presented by Suganya Karunakaran](https://reader034.vdocuments.mx/reader034/viewer/2022051622/56814ef8550346895dbc8aef/html5/thumbnails/7.jpg)
Computational Consequence May fundamentally chance dendrite
integration properties Reduced membrane time constant –
change in Temporal Processing
![Page 8: Presented by Suganya Karunakaran](https://reader034.vdocuments.mx/reader034/viewer/2022051622/56814ef8550346895dbc8aef/html5/thumbnails/8.jpg)
Previous Results
Effects of background synaptic conductance activity on ISI variability depends on neuron type
For a conductance based stimulus, In pyramidal cells lacking spike frequency
adaptation, variability increased In pyramidal cells displaying spike frequency
adaptation, variability decreased
(τ differs between two subtypes) Leak – bifurcation parameter
Reduces afterdepolarization (ADP) Decrease the gain of frequency-current
relationship
![Page 9: Presented by Suganya Karunakaran](https://reader034.vdocuments.mx/reader034/viewer/2022051622/56814ef8550346895dbc8aef/html5/thumbnails/9.jpg)
Model
![Page 10: Presented by Suganya Karunakaran](https://reader034.vdocuments.mx/reader034/viewer/2022051622/56814ef8550346895dbc8aef/html5/thumbnails/10.jpg)
Model ctnd.
![Page 11: Presented by Suganya Karunakaran](https://reader034.vdocuments.mx/reader034/viewer/2022051622/56814ef8550346895dbc8aef/html5/thumbnails/11.jpg)
Parameters
![Page 12: Presented by Suganya Karunakaran](https://reader034.vdocuments.mx/reader034/viewer/2022051622/56814ef8550346895dbc8aef/html5/thumbnails/12.jpg)
Non adapting Cells
The ability of a high conductance state to increase ISI variability depends on the subtype of pyramidal cell.
![Page 13: Presented by Suganya Karunakaran](https://reader034.vdocuments.mx/reader034/viewer/2022051622/56814ef8550346895dbc8aef/html5/thumbnails/13.jpg)
Model
3 Dimensions V h (INa inactivation ) n (IKCa activation)
Single pulse-excited spike produces a larger ADP under control conditions than with added leak conductance
![Page 14: Presented by Suganya Karunakaran](https://reader034.vdocuments.mx/reader034/viewer/2022051622/56814ef8550346895dbc8aef/html5/thumbnails/14.jpg)
Single pulse Excitation
Matlab Model- Reproduced Result
![Page 15: Presented by Suganya Karunakaran](https://reader034.vdocuments.mx/reader034/viewer/2022051622/56814ef8550346895dbc8aef/html5/thumbnails/15.jpg)
Decrease in CV
![Page 16: Presented by Suganya Karunakaran](https://reader034.vdocuments.mx/reader034/viewer/2022051622/56814ef8550346895dbc8aef/html5/thumbnails/16.jpg)
Phase Plane Analysis - Control
Blue – Stable fixed pointBlack – Unstable fixed point
Reproduced Result
![Page 17: Presented by Suganya Karunakaran](https://reader034.vdocuments.mx/reader034/viewer/2022051622/56814ef8550346895dbc8aef/html5/thumbnails/17.jpg)
Reproduced Result
Phase Plane Analysis – with leak
![Page 18: Presented by Suganya Karunakaran](https://reader034.vdocuments.mx/reader034/viewer/2022051622/56814ef8550346895dbc8aef/html5/thumbnails/18.jpg)
Phase Plane Analysis
![Page 19: Presented by Suganya Karunakaran](https://reader034.vdocuments.mx/reader034/viewer/2022051622/56814ef8550346895dbc8aef/html5/thumbnails/19.jpg)
Bifurcation Analysis
![Page 20: Presented by Suganya Karunakaran](https://reader034.vdocuments.mx/reader034/viewer/2022051622/56814ef8550346895dbc8aef/html5/thumbnails/20.jpg)
Conclusion
The decrease in CV of the model with added leak conductance can be explained as a consequence of a lower gain in the F-I relationship resulting from the changes in the ADP and bifurcation in the fast subsystem of the model
![Page 21: Presented by Suganya Karunakaran](https://reader034.vdocuments.mx/reader034/viewer/2022051622/56814ef8550346895dbc8aef/html5/thumbnails/21.jpg)