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Reward motivation accelerates the onset of neural novelty signals in humans to 85 milliseconds.

ABSTRACT: The neural responses that distinguish novel from familiar items in recognition memory tasks are remarkably fast in both humans and nonhuman primates. In humans, the earliest onsets of neural novelty effects emerge at about approximately 150-200 ms after stimulus onset. However, in recognition memory studies with nonhuman primates, novelty effects can arise at as early as 70-80 ms. Here, we address the possibility that this large species difference in onset latencies is caused experimentally by the necessity of using reward reinforcement to motivate the detection of novel or familiar items in nonhuman primates but not in humans. Via magnetoencephalography in humans, we show in two experiments that the onset of neural novelty signals is accelerated from approximately 200 ms to approximately 85 ms if correct recognition memory for either novel or familiar items is rewarded. Importantly, this acceleration is independent of whether the detection of the novel or the familiar scenes is rewarded. Furthermore, this early novelty effect contributed to memory retrieval because neural reward responses, which were contingent upon novelty detection, followed approximately 100 ms later. Thus, under the contextual influence of reward motivation, behaviorally relevant novelty signals emerge much faster than previously held possible in humans.

SUBMITTER: Bunzeck N

PROVIDER: S-EPMC2764383 | biostudies-literature | 2009 Aug

REPOSITORIES: biostudies-literature

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Reward motivation accelerates the onset of neural novelty signals in humans to 85 milliseconds.

Bunzeck Nico N Doeller Christian F CF Fuentemilla Lluis L Dolan Raymond J RJ Duzel Emrah E

Current biology : CB 20090702 15

The neural responses that distinguish novel from familiar items in recognition memory tasks are remarkably fast in both humans and nonhuman primates. In humans, the earliest onsets of neural novelty effects emerge at about approximately 150-200 ms after stimulus onset. However, in recognition memory studies with nonhuman primates, novelty effects can arise at as early as 70-80 ms. Here, we address the possibility that this large species difference in onset latencies is caused experimentally by t ...[more]

PMID: 19576774

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Project description:As the stream of experience unfolds, our memory system rapidly transforms current inputs into long-lasting meaningful memories. A putative neural mechanism that strongly influences how input elements are transformed into meaningful memory codes relies on the ability to integrate them with existing structures of knowledge or schemas. However, it is not yet clear whether schema-related integration neural mechanisms occur during online encoding. In the current investigation, we examined the encoding-dependent nature of this phenomenon in humans. We showed that actively integrating words with congruent semantic information provided by a category cue enhances memory for words and increases false recall. The memory effect of such active integration with congruent information was robust, even with an interference task occurring right after each encoding word list. In addition, via electroencephalography, we show in 2 separate studies that the onset of the neural signals of successful encoding appeared early (∼400 ms) during the encoding of congruent words. That the neural signals of successful encoding of congruent and incongruent information followed similarly ∼200 ms later suggests that this earlier neural response contributed to memory formation. We propose that the encoding of events that are congruent with readily available contextual semantics can trigger an accelerated onset of the neural mechanisms, supporting the integration of semantic information with the event input. This faster onset would result in a long-lasting and meaningful memory trace for the event but, at the same time, make it difficult to distinguish it from plausible but never encoded events (i.e., related false memories).Significance statementConceptual or schema congruence has a strong influence on long-term memory. However, the question of whether schema-related integration neural mechanisms occur during online encoding has yet to be clarified. We investigated the neural mechanisms reflecting how the active integration of words with congruent semantic categories enhances memory for words and increases false recall of semantically related words. We analyzed event-related potentials during encoding and showed that the onset of the neural signals of successful encoding appeared early (∼400 ms) during the encoding of congruent words. Our findings indicate that congruent events can trigger an accelerated onset of neural encoding mechanisms supporting the integration of semantic information with the event input.

Dataset Information

Reward motivation accelerates the onset of neural novelty signals in humans to 85 milliseconds.

Publications

Reward motivation accelerates the onset of neural novelty signals in humans to 85 milliseconds.

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