Ready for action! When the brain learns, yet memory-biased action does not follow

Does memory prepare us to act? Long-term memory can facilitate signal detection, though the degree of benefit varies and can even be absent. To dissociate between learning and behavioral expression of learning, we used high-density electroencephalography (EEG) to assess memory retrieval and response processing. At learning, participants heard everyday sounds. Half of these sound clips were paired with an above-threshold lateralized tone, such that it was possible to form incidental associations between the sound clip and the location of the tone. Importantly, attention was directed to either the sound clip (Experiment 1) or the tone (Experiment 2). Participants then completed a novel detection task that separated cued retrieval from response processing. At retrieval, we observed a striking brain-behavior dissociation. Learning was observed neurally in both experiments. Behaviorally, however, signal detection was only facilitated in Experiment 2, for which there was an accompanying explicit memory for tone presence. Further, implicit neural memory for tone location correlated with the degree of response preparation, but not response execution. Together, the findings suggest 1) that attention at learning affects memory-biased action and 2) that memory prepared action via both explicit and implicit associative memory, with the latter triggering response preparation.