Electrophysiological underpinnings of reward processing: Are we exploiting the full potential of EEG?

• Published in: NeuroImage (Orlando, Fla.) Vol. 242; no. 4; p. 118478
• Main Authors: Meyer, Garance M., Marco-Pallarés, Josep, Boulinguez, Philippe, Sescousse, Guillaume
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 15.11.2021; Elsevier Limited; Elsevier
• Subjects: Anticipation, Psychological - physiology; Brain - physiology; Cognition & reasoning; Cognitive ability; EEG; Electroencephalography; Electroencephalography - methods; Event-related potentials; Evoked Potentials - physiology; Feedback; Humans; Life Sciences; Localization; Medical imaging; Motivation; Neuroimaging; Oscillations; Reinforcement; Reward; Signal processing; Source separation; Spatial discrimination; Oscillations; Source separation; Electroencephalography; Reward; Feedback; Reward Feedback Electroencephalography Oscillations Source separation
• ISSN: 1053-8119; 1095-9572; 1095-9572
• DOI: 10.1016/j.neuroimage.2021.118478

•359 EEG studies of reward processing were surveyed.•Reward anticipation has been overlooked with regard to reward receipt (24% vs 88%).•Feedback-related ERPs are still the dominant analytical approach in the field (92%).•As a result, current methods provide limited and biased insight into reward processing.•We call for studies combining source separation, localization and spectral analyses. Understanding how the brain processes reward is an important and complex endeavor, which has involved the use of a range of complementary neuroimaging tools, including electroencephalography (EEG). EEG has been praised for its high temporal resolution but, because the signal recorded at the scalp is a mixture of brain activities, it is often considered to have poor spatial resolution. Besides, EEG data analysis has most often relied on event-related potentials (ERPs) which cancel out non-phase locked oscillatory activity, thus limiting the functional discriminative power of EEG attainable through spectral analyses. Because these three dimensions -temporal, spatial and spectral- have been unequally leveraged in reward studies, we argue that the full potential of EEG has not been exploited. To back up our claim, we first performed a systematic survey of EEG studies assessing reward processing. Specifically, we report on the nature of the cognitive processes investigated (i.e., reward anticipation or reward outcome processing) and the methods used to collect and process the EEG data (i.e., event-related potential, time-frequency or source analyses). A total of 359 studies involving healthy subjects and the delivery of monetary rewards were surveyed. We show that reward anticipation has been overlooked (88% of studies investigated reward outcome processing, while only 24% investigated reward anticipation), and that time-frequency and source analyses (respectively reported by 19% and 12% of the studies) have not been widely adopted by the field yet, with ERPs still being the dominant methodology (92% of the studies). We argue that this focus on feedback-related ERPs provides a biased perspective on reward processing, by ignoring reward anticipation processes as well as a large part of the information contained in the EEG signal. Finally, we illustrate with selected examples how addressing these issues could benefit the field, relying on approaches combining time-frequency analyses, blind source separation and source localization.