Systems memory consoliation

Systems memory consoliation

where temporary memories, initially stored in the hippocampus, are gradually reorganized and transferred to the neocortex for long-term, stable storage.

consolidation should be a gradual interleaved process.

Recent memory

HP (sparse, precise codes): fast, one-time learning

remote memory

neocortex (distributed, redundant codes): gradual, interleaved learning

Two major sleep stages

Slow wave sleep and rapid eye movement sleep

Slow wave sleep

Acetylcholine down

noradrenaline/serotonin no change

cortisol down

REM sleep

Acteylcholine up

noradrenaline/serotonin down

cortisol up

Sharp wave ripples

in SWS. Most prominent phenomemnon in HP (cannot be missed). very fast. almost all the spikes occuring together with ripples.

reactivation in SWS

cells that fired together when the animal occupued particular locations in the environement exhibited an increased tendency to fire together during subsequent sleep, in compariosn to sleep episodes preceding the behavioral tasks. Cells that were inactive during behvaior or that were active but had non-overlapping spatial firing, did not show this increase.

reactivation becomes a sequence replay during SWS

when animal is run left to right, you can line up cells as see them fire sequentially. Will those same cells also persist or spiking patterns exist during SWS. there is significant replay of the actual sequence of a bunch of place cells in SWS.

coordinated sequence replay between HP and visual cortex during SWS

HP and cortex activate same trajectory in space. In visual cortex there is a sequence. This supports the SMC. Overall during the sleep the activity in HP is organized into active and silent period, also called up and down state. in cortex this up and down state is much more prominent.

is reactivation occuring in REM sleep?

animal is doing a task, buunch of HP place cells with patterns doing the task. look at the same neurons during REM sleep, noisier than SWS while compared but still basically matches. REM replay at the neuroactivity level exists.

odor cues during SWS

task is for subjects to play a memory game. Sleep stage. used sensory cues to make the human subject reactivate. Sensory cue was odor. While they begin to sleep they play same odor cue when sleeping. they played with odor early/late, no odor, odor during wake period then sleep. in the retirval stage try to match same ones. Memory performance trippled during odor during learning and SWS. odor can enhance memory during SWS by reactivation.

causal relationship between reactivation and memory consolidation

In three minutes mice has to find the three arms baited. put animal to sleep, during the sleep period, whenevr ripple happens you can deliver stimulation to disrupt the diring for about 150 ms, and also do control stimulation. for the test, stimulation disrupted and performance of learning was lower. memroy consolidaiton is required for memory curve.