COERULEUS MOTIVATED MEMORY 1 1 2 3 4 5 Locus coeruleus activity strengthens prioritized 6 memories under arousal

34 Recent models posit that bursts of locus coeruleus (LC) activity amplify neural gain, such that 35 limited attention and encoding resources focus even more on prioritized mental representations 36 under arousal. Here, we tested this hypothesis in human males and females using functional 37 magnetic resonance imaging (fMRI), neuromelanin MRI, and pupil dilation, a biomarker of 38 arousal and LC activity. During scanning, participants performed a monetary incentive encoding 39 task in which threat of punishment motivated participants to prioritize encoding of scene images 40 over superimposed objects. Threat of punishment elicited arousal and selectively enhanced 41 memory for goal-relevant scenes. Furthermore, trial-level pupil dilations predicted better scene 42 memory under threat, but were not related to object memory outcomes. FMRI analyses 43 revealed that greater threat-evoked pupil dilations were positively associated with greater scene 44 encoding activity in LC and parahippocampal cortex, a region specialized to process scene 45 information. Across participants, this pattern of LC engagement for goal-relevant encoding was 46 correlated with neuromelanin signal intensity, providing the first evidence that LC structure 47 relates to its activation pattern during cognitive processing. Threat also reduced dynamic 48 functional connectivity between high (parahippocampal place area) and lower priority (lateral 49 occipital cortex) category-selective visual cortex in ways that predicted increased memory 50 selectivity. Together these findings support the idea that, under arousal, LC activity selectively 51 strengthens prioritized memory representations by modulating local and functional network-level 52 patterns of information processing. 53 54 55 RUNNING HEAD: LOCUS COERULEUS MOTIVATED MEMORY 3 Significance Statement 56 Adaptive behavior relies on the ability to select and store important information amidst 57 distraction. Prioritizing encoding of task-relevant inputs is especially critical in threatening or 58 arousing situations, when forming these memories is essential for avoiding danger in the future. 59 However, little is known about the arousal mechanisms that support such memory selectivity. 60 Using fMRI, neuromelanin MRI, and pupil measures, we demonstrate that locus coeruleus (LC) 61 activity amplifies neural gain, such that limited encoding resources focus even more on 62 prioritized mental representations under arousal. For the first time, we also show that LC 63 structure relates to its involvement in threat-related encoding processes. These results shed 64 new light on the mechanisms by which we process important information when it is most 65 needed. 66 67