Enhanced transformation of incidentally learned knowledge into explicit memory by dopaminergic modulation

Abstract

During incidental learning statistical regularities are extracted from the environment without the intention to learn. Acquired implicit memory of these regularities can affect behavior in the absence of awareness. However, conscious insight in the underlying regularities can also develop during learning. Such emergence of explicit memory is an important learning mechanism that is assumed to involve prediction errors in the striatum and to be dopamine-dependent. Here we directly tested this hypothesis by manipulating dopamine levels during incidental learning in a modified serial reaction time task (SRTT) featuring a hidden regular sequence of motor responses in a placebo-controlled between-group study. Awareness for the sequential regularity was subsequently assessed using cued generation and additionally verified using free recall. The results demonstrated that dopaminergic modulation nearly doubled the amount of explicit sequence knowledge emerged during learning in comparison to the placebo group. This strong effect clearly argues for a causal role of dopamine-dependent processing for the development of awareness for sequential regularities during learning.

Dopamine Enhances Item Novelty Detection via Hippocampal and Associative Recall via Left Lateral Prefrontal Cortex Mechanisms

“…We had to use a between-group design rather than a more powerful within-group crossover design because of the limited stimulus set and possible interference effects between the picture-word pairs. Additionally, also another task measured in this sample (Clos et al, 2018) was incompatible with a within-group design. Fifty-three of these participants (13 males, mean age 24 Ϯ 2.9 years; 27 haloperidol and 26 placebo) took part in the cued association recall paradigm.…”

“…We used a double-blind, placebo-controlled between-group design with 54 participants in total as part of a larger study (Clos et al, 2018(Clos et al, , 2019. We had to use a between-group design rather than a more powerful within-group crossover design because of the limited stimulus set and possible interference effects between the picture-word pairs.…”

“…This study was part of a series of randomized, placebo-controlled pharmacological experiments (Clos et al, 2018(Clos et al, , 2019 in which dopamine level was manipulated by 2 mg of the D2-antagonist haloperidol. Importantly, such acute low doses of D2-antagonists are thought to preferably block presynaptic D2-autoreceptors (Frank and O'Reilly, 2006;Knutson and Gibbs, 2007;Clos et al, 2018Clos et al, , 2019, which regulate dopamine release (Ford, 2014). Therefore, their blockade potentiates phasic dopamine release (Dugast et al, 1997;Pehek, 1999;Jaworski et al, 2001;Garris et al, 2003;Chen et al, 2005).…”

Dopamine is a double-edged sword: dopaminergic modulation enhances memory retrieval performance but impairs metacognition

“…In particular, encoding and consolidation of memories require the stimulation of dopamine receptors as part of a hippocampal-striatal-prefrontal loop that orchestrates the formation of new memories [2,3]. Dopaminergic effects on working memory (WM) are well established in animals and humans [4], but dopamine has also been reported to affect other domains of memory (e.g., [5,6]). For episodic memory, while several pharmacological studies reported dopaminergic effects on encoding or consolidation [7][8][9][10], effects on retrieval performance were often absent or inconclusive [11][12][13][14][15].…”

Effects of short-term arm immobilization on motor skill acquisition

“…A version of the Serial Reaction Time Task (SRTT) [27,28], an implicit motor task, modified from Clos and Sommer was used in this study [29]. Participants placed the fingers of their left (non-dominant) hand on a custom-made button box.…”