Sleep deprivation has been shown recently to alter emotional processing possibly associated with reduced frontal regulation. Such impairments can ultimately fail adaptive attempts to regulate emotional processing (also known as cognitive control of emotion), although this hypothesis has not been examined directly. Therefore, we explored the influence of sleep deprivation on the human brain using two different cognitive-emotional tasks, recorded using fMRI and EEG. Both tasks involved irrelevant emotional and neutral distractors presented during a competing cognitive challenge, thus creating a continuous demand for regulating emotional processing. Results reveal that, although participants showed enhanced limbic and electrophysiological reactions to emotional distractors regardless of their sleep state, they were specifically unable to ignore neutral distracting information after sleep deprivation. As a consequence, sleep deprivation resulted in similar processing of neutral and negative distractors, thus disabling accurate emotional discrimination. As expected, these findings were further associated with a decrease in prefrontal connectivity patterns in both EEG and fMRI signals, reflecting a profound decline in cognitive control of emotion. Notably, such a decline was associated with lower REM sleep amounts, supporting a role for REM sleep in overnight emotional processing. Altogether, our findings suggest that losing sleep alters emotional reactivity by lowering the threshold for emotional activation, leading to a maladaptive loss of emotional neutrality.

Numerous neuroimaging studies have implicated default mode network (DMN) involvement in both internally driven processes and memory. Nevertheless, it is unclear whether memory operations reflect a particular case of internally driven processing or alternatively involve the DMN in a distinct manner, possibly depending on memory type. This question is critical for refining neurocognitive memory theorem in the context of other endogenic processes and elucidating the functional significance of this key network. We used functional MRI to examine DMN activity and connectivity patterns while participants overtly generated words according to nonmnemonic (phonemic) or mnemonic (semantic or episodic) cues. Overall, mnemonic word fluency was found to elicit greater DMN activity and stronger within-network functional connectivity compared with nonmnemonic fluency. Furthermore, two levels of functional organization of memory retrieval were shown. First, across both mnemonic tasks, activity was greater mainly in the posterior cingulate cortex, implying selective contribution to generic aspects of memory beyond its general involvement in endogenous processes. Second, parts of the DMN showed distinct selectivity for each of the mnemonic conditions; greater recruitment of the anterior prefrontal cortex, retroesplenial cortex, and hippocampi and elevated connectivity between anterior and posterior medial DMN nodes characterized the semantic condition, whereas increased recruitment of posterior DMN components and elevated connectivity between them characterized the episodic condition. This finding emphasizes the involvement of DMN elements in discrete aspects of memory retrieval. Altogether, our results show a specific contribution of the DMN to memory processes, corresponding to the specific type of memory retrieval.free recall | memory search | word fluency T he default mode network (DMN) is known to play a central role in internally based processes, including self-referential operations (1-4), internal mentation (5), and unconstrained thinking (6, 7). Additionally, during the past decades, the DMN has consistently been implicated in both semantic (8, 9) and episodic (10-13) memory processes. However, despite the fact that internal operations are inherent to many, if not all, mnemonic tasks, the unique contributions of the DMN to memory operations beyond its more general role in nonmnemonic internally based processes have not been sufficiently addressed thus far.One example of an internally based mnemonic process is mental search, which plays a central role in memory retrieval (14). Although a significant contribution of the DMN to memory search has been shown (12, 15), it is yet unclear whether this contribution merely reflects the DMN's involvement in nonspecific internal direction of attention or rather, a specific role for the DMN in mnemonic search processes. Direct comparison of DMN recruitment during memory search with its recruitment during nonmnemonic internal search operations may shed light on this matter. This questi...

Increased brain activation in patients with SLE during learning may reflect compensatory mechanisms to overcome memory impairment. Our findings localize this impairment to the amPFC, consistent with the behavioral pattern seen in SLE. Altered networking of the hippocampal subsystem of the DMN is consistent with hippocampal neuronal damage seen in SLE, and may reflect compensatory cortical reorganization to cope with dysfunction in these regions pivotal to mnemonic functions.

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