IDENTIFYING ELECTROENCEPHALOGRAPHIC INDICES OF STAGES OF REWARD MEMORY (ACQUISITION, RETRIEVAL AND PREDICTION ERROR) AND FUTURE IMPLICATIONS FOR THERAPEUTIC MEMORY RECONSOLIDATION
Authors: Ofori *Shelan Zaynah , Harding Rebecca , Das Ravi 
Published: February 2025

Abstract

Background
While there are some evidence-based treatments for substance use disorders (SUDs), maintaining abstinence remains a largely unmet challenge. Current treatments focus on the short-term and management of withdrawal symptoms. However, do not tackle the maladaptive environmental factors, nor neuropsychopharmacological changes, that predispose individuals to relapse. Contemporary models of addictive behaviour place aberrant reward learning at the heart of the pathogenesis and maintenance of SUDs. Recently, attention has focussed on the process of reconsolidation in memory maintenance and suppression. Reconsolidation offers a therapeutic window in which to directly target (and weaken) maladaptive motivational memory traces that promote relapse susceptibility, conferring longer-lasting protection against relapse1. Despite the recognised promise of ‘memory therapeutics’, their implementation is currently hampered by a lack of candidate biomarkers/measures that index different reward memory processes.

Aims & Objectives
This review (PROPSERO:CRD42022359768) aims to provide a comprehensive synthesis of electroencephalographic (EEG) signals that have been found to index key theoretical processes involved in stages of associative reward memory. It aims to provide a reference for the encephalographic correlates of reward memory and identify EEG neural-signatures that may act as biomarkers to quantify reward memory processes.

Methods
Four databases were searched: PubMed, Science Direct, Embase and MEDLINE. Search terms tapped into four key ‘stages’ of associative reward memory: (i) learning (ii) retrieval (iii) destabilization and/or reconsolidation (iv) extinction. Studies had to report EEG activity during a relevant reward memory process and include data from human participants who were healthy; ‘at-risk’ (with high but subclinical levels of substance use or gambling); or suffering from a substance use or gambling disorder.

Results
Of the 7604 articles screened, 46 were included with a total number of 1531 participants. All 46 of the included studies used only a ‘healthy’ participant population. Table 1 summarises ERP results from the included studies.

Discussion & Conclusion
Amongst reward memory retrieval studies, P300 and N400 EEG components were consistently of significance. Reward learning studies identified theta power, P300 and N500 EEG components; and prediction error studies identified delta power, P300 and N500 as being key during processing. These aforementioned components should be utilized as key signals for predicting participant outcomes during memory reconsolidation interventions in individuals with hazardous or harmful drinking patterns.

References
[1]Das, R.K. et al. (2018) ‘A prediction error-driven retrieval procedure for destabilizing and rewriting maladaptive reward memories in Hazardous Drinkers’, Journal of Visualized Experiments [Preprint], (131). doi:10.3791/56097.