Electrophysiological investigation of reward anticipation and outcome evaluation during slot machine play

Abstract

Slot machines are a popular form of gambling, offering a tractable way to experimentally model reward processes. This study used a 3-reel slot paradigm to assess psychologically distinct phases of reward processing, reflecting anticipation, and early and late-stage outcome processing. EEG measures of winning, nearly missing (a losing outcome revealed at the final, third reel), and “totally” missing (a losing outcome revealed earlier, at the second reel) were collected from healthy adults (n=54). Condition effects were evaluated in: i) event-related potential (ERP) components reflecting anticipatory attention (stimulus preceding negativity, SPN) and outcome processing (reward positivity, RewP and late-positive potential, LPP) and ii) total power and phase synchrony of theta and delta band oscillations. Behaviorally, trial initiation was fastest after a near miss outcome and slowest after a winning outcome. As expected, a significant SPN was observed for possible wins (AA) vs. total misses (AB), consistent with reward anticipation. In addition, significantly larger win (AAA) vs. near miss (AAB) amplitudes were observed for the RewP and LPP to wins and LPP to near misses (vs. total misses) reflecting early and late-stage outcome processing effects. There was an effect of reel position on the RewP, with larger effects in the final reel (AAA-AAB) relative to the 2nd-reel locked difference waves (AA-AB). Across all outcomes, near misses elicited the largest and most phase-synchronized theta responses, while wins elicited larger and more phase-synchronized delta responses than total misses, with near misses not differing from wins or total misses. Phase locking measures contrasting win vs. near miss delta and theta synchronization, within time windows corresponding to ERP measurements, covaried with RewP, but not SPN or LPP, amplitude. Lastly, EEG measures showed differential relationships with age and self-reported consummatory pleasure. In the context of slot machine play, where reward anticipation and attainment place minimal demands on effort and skill, ERP and time-frequency methods capture distinct neurophysiological signatures of reward anticipation and outcome processing.

Reward processing electrophysiology in schizophrenia: Effects of age and illness phase

“…2 ( Supplemental Materials ). As reported in ( Fryer et al, 2020 ), HC showed the expected condition effects for SPN, i.e., more negative for anticipated wins than total misses (AA < AB), and the expected condition effects for RewP and LPP, i.e., more positive for wins than near misses (AAA > AAB).

Fig.

…”

“…3 F; Table S2 ), compared to the HC pattern of greater LPP responses to wins versus near misses ( Fig. 3 E) ( Fryer et al, 2020 ), and the CSZ group, which showed no age-adjusted LPP condition difference.…”

“…Illness phase differences emerged during later reward outcome processing. More specifically, ESZ had larger LPP responses following near misses than wins, a reversal of the HC pattern ( Fryer et al, 2020 ). This alteration was specific to ESZ, as the CSZ group showed no age-adjusted LPP differences.…”

“…Fifty-four individuals with SZ (76% men; age range = 19.07–64.70 years) and 54 HC (78% men; age range = 19.25–64.41 years) were recruited via community advertisements; results from the HC sample are described in a previous study ( Fryer et al, 2020 ). SZ subjects were either early illness (ESZ) within 5 years of onset ( Fryer et al, 2016 , Fryer et al, 2013 , Hay et al, 2015 ) ( n = 26; mean illness duration = 2.90 ± 1.47 years), or chronic (CSZ; n = 28; mean illness duration = 23.55 ± 15.35 years).…”

“…We developed a 288-trial slot-machine reward task adapted from prior studies ( Habib and Dixon, 2010 , Clark et al, 2009 , Donkers et al, 2005 ), and shown to elicit expected SPN, RewP, and LPP condition effects in the same HC sample studied here ( Fryer et al, 2020 ). Subjects initiated each trial via a button press, after which reels 1–3 (R1, R2, R3) populated automatically from left to right with single, sequential fruit symbols.…”