Reconciling forgetting and memory consolidation: simulating the dissociable effects of neuronal noise levels on cortical memory traces.

Garagnani, M. and Lucchese, G.. 2021. 'Reconciling forgetting and memory consolidation: simulating the dissociable effects of neuronal noise levels on cortical memory traces.'. In: 30th Annual Computational Neuroscience Meeting (CNS-2021). Online 3 - 7 July 2021. [Conference or Workshop Item] (Forthcoming)

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Abstract or Description

Neuronal noise as resulting from spontaneous baseline firing is believed to play an important role in cognitive processes, with theories postulating a contribution to gradual memory trace decay (forgetting). However, the exact cortical mechanisms underlying this process remain unclear. Specifically, transcranial direct current stimulation (tDCS) has been shown to promote memory consolidation; furthermore, a moderate degree of neural noise has also been suggested to positively affect memory consolidation, whereas high degrees of noise are suspected to negatively interfere with it.
To shed light on the exact cortical mechanisms underlying the differential contributions of low and high neural noise to memory consolidation (and decay) in the neocortex, we used a deep, spiking, neurobiologically constrained computational model of primary, secondary and associative areas in frontal and temporal lobes of the human brain. The network's "primary cortices" were repeatedly confronted with model-correlate of perception and action patterns, while strengths of all synaptic links were allowed to change by means of neurobiologically realistic learning mechanisms. This lead to the emergence of stimulus-specific cell assembly (CA) memory circuits in it, binding together perception and action inputs. To simulate the effects of noise on such memory traces, after the training two identical copies of the model were subjected to a period of constant high (or low) intensity noise, respectively, while synapses remained plastic.
Intriguingly, we observed that high noise levels induced rapid decay of previously formed CA memory traces in the network, whereas low noise levels lead to further CA-circuit consolidation. Preliminary analyses suggested that this behaviour was a result of the periodic re-activation of the model's memory circuits, which was observed in the low-noise condition but not in the high-noise one. We conjectured that, while a relatively small amount of noise allowed ignition (and hence consolidation) of the existing memory circuits to occur, too much prevented it (due to the network's inhibitory response to exceedingly high noise levels). These observations were confirmed by statistical analyses of changes in high-frequency oscillatory activity of the network during CA circuit stimulation.
The present results provide a neuromechanistic account able to bridge the gap between theories of forgetting and current experimental data on memory consolidation and brain stimulation effects.

Item Type:

Conference or Workshop Item (Poster)

Departments, Centres and Research Units:

Computing

Dates:

DateEvent
31 May 2021Accepted
5 July 2021Completed

Event Location:

Online

Date range:

3 - 7 July 2021

Item ID:

30118

Date Deposited:

04 Jun 2021 12:06

Last Modified:

05 Jul 2021 21:20

URI:

https://research.gold.ac.uk/id/eprint/30118

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