Luke Atack¹, Stephen Emrich¹; ¹Brock University

While much is known about how information is encoded, maintained, and manipulated in visual working memory (VWM), little is known about the underlying principle that guides retrieval from VWM. It has been proposed that retrieval from VWM is of an accumulation-to-bound decision process whereby evidence for potential decisions is gradually accumulated until a threshold is met, yet neural evidence for this process remains lacking. Research into perceptual decision making – the sampling of external stimuli towards a decision – has indicated that the P3b, an electroencephalography (EEG) event related potential (ERP), reflects an accumulation-to-bound decision process. That is, (1) reaction time and decision difficulty influence the slope of the P3b going into response and (2) the P3b has uniform amplitude at response, regardless of reaction time and decision difficulty. Here, we investigate whether the P3b will display similar characteristics when retrieving items from VWM as it does during perceptual decision making. To do this, 19 participants (Mage = 20.6, SDage = 2.8, 7 male) completed a change detection task with varying VWM load while EEG data was recorded. Consistent with the decision-making framework of gradual evidence accumulation, we show that (1) slower reaction times and greater VWM load have a steeper incline in the P3b and (2) the P3b has a uniform amplitude at response, regardless of reaction time, but not VWM load. This suggests that (1) evidence accumulation as reflected in the slope of the P3b is influenced by reaction time and decision difficulty and (2) P3b amplitude at response reflects a fixed decision threshold regardless of reaction time, but not decision difficulty. These results provide neurophysiological evidence that sampling of internal representations towards a decision is akin to the sampling of external sensations towards a decision.

Acknowledgements: This work was supported by a National Science and Research Council of Canada Discovery Grant