The Paradoxical Effect of Deep Brain Stimulation on Memory

Abstract

Deep brain stimulation (DBS) is a promising treatment for many memory-related disorders including dementia, anxiety, and addiction. However, the use of DBS can be a paradoxical conundrumdementia treatments aim to improve memory, whereas anxiety or addiction treatments aim to suppress maladaptive memory. In this review, the key hypotheses on how DBS affects memory are highlighted. We consolidate the findings and conclusions from the current research on the effects of DBS on memory in attempt to make sense of the bidirectional nature of DBS in disrupting and enhancing memory. Based on the current literature, we hypothesize that the timing of DBS plays a key role in its contradictory effects, and therefore, we propose a consolidated model of how DBS can both disrupt and enhance memory.

Dropout in Neural Networks Simulates the Paradoxical Effects of Deep Brain Stimulation on Memory

“…An early hypothesis of the mechanism of DBS was that it creates a temporary neural activity lesion, and we further showed that prelimbic cortex DBS was associated with the disruption of memory and a drop in the neural activity marker c-fos in the ventral hippocampus [6]. Dropout of neural nodes, while congruent with the disruption of memory, has not played a major role in the mechanistic understanding of memory enhancement seen in DBS (though it should be noted that other mechanism such as neurogenesis and wave syncing have been suggested [3]). In this paper, we propose that DBS causes dropout in neural nodes that "forces" the activation of new pathways and creates more robust networks, similar to how dropout enhanced the neural networks.…”

“…We have previously argued that timing plays an important role in the outcome of DBS on memory [3]; DBS applied post or during behaviour testing tended to disrupt memory, whereas DBS applied prior to behaviour testing tended to enhance memory. However, the mechanisms behind these outcomes are still relatively unknown.…”

“…However, memory systems can fall into disease when expressed pervasively (e.g., anxiety or addiction) or degenerated (e.g., dementia)-both of which are major health challenges worldwide [1,2]. Neuromodulation techniques such as Deep Brain Stimulation (DBS) have shown promising results as treatments for such memory-related disorders [3,4], yet the mechanisms behind these effects are still largely unknown. Furthermore, the effects of treatments such as DBS appear to be paradoxical, in that they can both disrupt [5,6] and enhance memories [7,8], even when applied to the same brain target [3].…”

Dropout in Neural Networks Simulates the Paradoxical Effects of Deep Brain Stimulation on Memory

“…We have previously argued that timing plays an important role in the outcome of DBS on memory (Tan et al, 2020b ). DBS applied post or during behavior testing tended to disrupt memory, whereas DBS applied prior to behavior testing tended to enhance memory.…”

“…However, memory systems can fall into disease when expressed pervasively (e.g., anxiety or addiction) or degenerate (e.g., dementia)—both of which are major health challenges worldwide (World Health Organization, 2012 , 2017 ). Neuromodulation techniques such as deep brain stimulation (DBS) have shown promising results as treatments for memory-related disorders (Tan et al, 2019b , 2020b ), yet the mechanisms behind these effects are still largely unknown. Furthermore, the effects of treatments such as DBS appear to be paradoxical, in that they can both disrupt (Hamani et al, 2010 ; Tan et al, 2019a ) and enhance memories (Hamani et al, 2011 ; Tan et al, 2020c ) even when applied to the same brain target (detailed review in Tan et al, 2020b ).…”