Switches in brain states in memory consolidation: a computational approach

(1)

• Change in NMDAr density occurs at a large timescale (required protein synthesis,…).

• Here we focus on change in NMDAr efficiency driven by a Ca-dependent synaptic plasticity rule.

I_int NMDA I_app GABA_A-B AMPA Presynaptic pulse Tonic Burst

Conductance based-model

• Dynamics of calcium entering NMDAr

Strong

connection

Mechanisms

• NMDA receptors (NMDAr)

Efficiency = Density = weak strong poor good [Shouval,2002] Exc. Inhib. Tonic Rest

LTP

LTD

Baseline #NMDAr #NMDAr Spik e

[Ca] = faster dynamics

At steady-state

Results

C D Transitory Synchron. bursting Bursting 10Hz Rest Ca_NMDA Ca_int Ca_int+ Ca_NMDA

Weak

connection

A _D A B C D C B 10Hz A B A B C D LTD threshold thresholdLTP

• The weak connection, characterized by a small amount of NMDAr, presents Ca oscillation during switch.

• The low Ca level triggers depression and reduces the synaptic efficiency. V_exc.

V_exc..

V_inhb.

Switches in brain states

2sec Reticular Relay EEG Pyramidal cell Up States Closer to firing threshold

Bursting Tonic Discharge

Slow-wave sleep Waking

Down States

How do switches in brain states affect

strong and weak synaptic connections ?

Inhb. Exc. NMOD [Zagha-McCormick,2014] Pre-

Post-NMDA Receptors

Long-term change in synaptic strength

Amount of NMDA receptors (NMDAr)

activation during tetanic stimulation

Associative memory | Learning

Mg

Ca_NMDA Ca_NMDA Ca_int

[Bear,2007]

+

-LTP

LTD

Strong connection

Weak connection = # NMDAr = [Ca]_{= # NMDAr = [Ca]}NMDA _NMDA

Kathleen Jacquerie, Guillaume Drion

Department of Electrical Engineering and Computer Science, University of Liege, Belgium

Switches in brain states in memory consolidation:

a computational model approach

kathleen.jacquerie@uliege.be

https://meet.google.com/ gkb-kuac-mjy

July 13 & 15

10:30-12:00 (GMT 0)

Switch is independent on synaptic connectivity

[Drion,2018]

5 sec

100

m

V

• Switch to burst provokes Ca oscillation.

• A relevant connection possesses a big amount of NMDAr leading to a large Ca fluctuation.

• This large Ca level encourages consolidation and stabilization of the synaptic efficiency.