Abstract
Capacity limitations in working memory (WM) necessitate the need to effectively control its contents. Here, we examined the effect of cabergoline, a dopamine D2 receptor agonist, on WM using a continuous report paradigm that allowed us to assess the fidelity with which items are stored. We assessed recall performance under three different gating conditions: remembering only one item, being cued to remember one target among distractors, and having to remember all items. Cabergoline had differential effects on recall performance according to whether distractors had to be ignored and whether mnemonic resources could be deployed exclusively to the target. Compared with placebo, cabergoline improved mnemonic performance when there were no distractors but significantly reduced performance when distractors were presented in a precue condition. No significant difference in performance was observed under cabergoline when all items had to be remembered. By applying a stochastic model of response selection, we established that the causes of drug-induced changes in performance were due to changes in the precision with which items were stored in WM. However, there was no change in the extent to which distractors were mistaken for targets. Thus, D2 agonism causes changes in the fidelity of mnemonic representations without altering interference between memoranda.
Highlights
Working memory (WM), the ability to store and manipulate information in the short term, is a limited capacity system that is essential to our daily lives (Baddeley, 2012; Oberauer & Hein, 2012)
We examined the effect of a D2 agonist, cabergoline, on recall precision using a double-blind crossover, placebo-controlled design
Given the limited capacity of WM (Fallon, Zokaei, & Husain, 2016), and it has been proposed that dopamine plays a crucial modulatory role in this process (Hazy et al, 2007; Frank & O’Reilly, 2006)
Summary
Working memory (WM), the ability to store and manipulate information in the short term, is a limited capacity system that is essential to our daily lives (Baddeley, 2012; Oberauer & Hein, 2012). Previous studies that have attempted to resolve this question have employed binary report measures, for example, change detection tasks requiring a same/different judgment at retrieval (Figure 1A) These methods effectively probe WM to determine whether an item has been retained, whereas recent techniques that measure precision of recall have suggested an alternative view to this all-or-nothing, “quantal” account (reviewed in Ma et al, 2014). We measured the quality of retained information by probing recall with an analog, continuous report scale (Gorgoraptis et al, 2011), rather than a binary one This allowed us to both examine raw performance differences induced by cabergoline and apply a probabilistic model to dissect out how different types of errors are affected by drugs
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