Academic journal article Cognitive, Affective and Behavioral Neuroscience

Monetary Rewards Influence Retrieval Orientations

Academic journal article Cognitive, Affective and Behavioral Neuroscience

Monetary Rewards Influence Retrieval Orientations

Article excerpt

Abstract Reward anticipation during learning is known to support memory formation, but its role in retrieval processes is so far unclear. Retrieval orientations, as a reflection of controlled retrieval processing, are one aspect of retrieval that might be modulated by reward. These processes can be measured using the event-related potentials (ERPs) elicited by retrieval cues from tasks with different retrieval requirements, such as via changes in the class of targeted memory information. To determine whether retrieval orientations of this kind are modulated by reward during learning, we investigated the effects of high and low reward expectancy on the ERP correlates of retrieval orientation in two separate experiments. The reward manipulation at study in Experiment 1 was associated with later memory performance, whereas in Experiment 2, reward was directly linked to accuracy in the study task. In both studies, the participants encoded mixed lists of pictures and words preceded by highor low-reward cues. After 24 h, they performed a recognition memory exclusion task, with words as the test items. In addition to a previously reported material-specific effect of retrieval orientation, a frontally distributed, reward-associated retrieval orientation effect was found in both experiments. These findings suggest that reward motivation during learning leads to the adoption of a reward-associated retrieval orientation to support the retrieval of highly motivational information. Thus, ERP retrieval orientation effects not only reflect retrieval processes related to the sought-for materials, but also relate to the reward conditions with which items were combined during encoding.

Keywords Event-related potentials . Reward-motivated learning . Retrieval orientation . Episodic memory

Humans are unique among animals in that they are able to acquire new knowledge both via the influence of direct reward and via the anticipation of remote reward. Changes in neuronal activation patterns that are driven by these processes of reward-motivated learning can take place even before new knowledge has been encountered (Adcock, Thangavel, Whitfield-Gabrieli, Knutson, & Gabrieli, 2006), and such changes are an important determinant of whether an event will be recovered at a later time (Sanquist, Rohrbaugh, Syndulko, & Lindsley, 1980). Previous brainimaging studies (Adcock et al., 2006; Wittmann et al., 2005) have indicated that two neural systems play a crucial role during reward-motivated learning: the mesolimbic system and the medial temporal lobes (MTL). Activation of the first system has been shown not only to redirect attention, but also to interact with hippocampal memory processes in the second system, mainly by activating dopaminergic pathways in the ventral tegmental area (VTA) and projections to the nucleus accumbens (NAcc) in the ventral striatum.

In one brain-imaging study, Wittmann et al. (2005) presented pictures that either cued possible monetary reward or were neutral. On reward trials, participants earned money for a correct and fast response in a subsequent reaction time task, whereas they lost money for an incorrect or slow response. After 3 weeks, an unexpected recognition memory test followed in which pictures that had previously been presented had to be discriminated fromnew, unstudied pictures. Reward anticipation during the reaction time task was found to activate brain regions associated with the dopaminergic system (mainly substantia nigra and striatum), which in turn coactivated the hippocampus (in MTL) and led to enhanced recognition memory performance. In a related fMRI study (Adcock et al., 2006), reward cues were incorporated into an intentional memory paradigm. The participants' task was to study pictures that were preceded by either a high- or a low-reward cue and to perform a visual-motor task on each trial. The cues indicated the amount of money that would be received for each correctly recognized study picture during a recognition test the next day. …

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