Abstract
Working memory (WM) performance varies substantially among individuals but the precise contribution of different WM component processes to these functional limits remains unclear. By analyzing different types of responses in a spatial WM task, we recently demonstrated a functional dissociation between confident and not-confident errors reflecting failures of WM encoding and maintenance, respectively. Here, we use event-related brain potentials to further explore this dissociation. Healthy participants performed a delayed orientation-discrimination task and rated their response confidence for each trial. The encoding-related N2pc component was significantly reduced for confident errors compared to confident correct responses, which is indicative of an encoding failure. In contrast, the maintenance-related contra-lateral delay activity was similar for these response types indicating that in confident error trials, WM representations – potentially the wrong ones – were maintained accurately and with stability throughout the delay interval. However, contra-lateral delay activity measured during the early part of the delay period was decreased for not-confident errors, potentially reflecting compromised maintenance processes. These electrophysiological findings contribute to a refined understanding of the encoding and maintenance processes that contribute to limitations in WM performance and capacity.
Highlights
Working memory (WM) allows us to actively hold and manipulate information in mind, making it available for a wide range of higher-order cognitive processes (Baddeley, 1986)
Our key findings derived from t-statistics are (i) that during WM encoding the target-related N2pc component was significantly reduced for IC responses compared to CC responses, whereas, (ii) the maintenance-related contralateral delay activity (CDA) component was similar for correct and incorrect responses when given with high confidence. (iii) In contrast, the amplitude of the early CDA was significantly reduced for IN responses relative to IC responses
By combining the analysis of different types of responses depending on the trial-to-trial level of self-reported subjective response confidence with electrophysiological measurements, we were in the present study able to disentangle the contribution of encoding and maintenance processes to the functional limits of WM performance
Summary
Working memory (WM) allows us to actively hold and manipulate information in mind, making it available for a wide range of higher-order cognitive processes (Baddeley, 1986). WM is viewed as emerging from the interplay between various component processes including encoding and maintaining information in WM (Bledowski et al, 2010; Eriksson et al, 2015), and WM performance failures can occur due to different reasons. To understand the functional limits to WM performance and capacity, it is crucial to disentangle the component processes that interact during different stages of a WM task (Jonides et al, 2008). Impaired early stage perceptual and attentional mechanisms contribute to reduced WM encoding and lower WM capacity for example in older persons (Gazzaley et al, 2005, 2008; Störmer et al, 2013) and in individuals with schizophrenia (Haenschel and Linden, 2011; Mayer et al, 2012)
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