TABLE 1.

Outstanding issues and questions.

1.	What role does the LHb play in memory processing by healthy brains? To answer this question, we need to better understand the precise short- vs. long-term roles of the mPFC and hippocampus in LHb memory processing. Also enhancing the ecologically-relevance and complexity of the behavioral assessments should facilitate our ability to further dissect the role of the LHb in memory.
2.	What types of context memory information are conveyed to the LHb from the mPFC and hippocampus, and how is this information modified during stress or neuropsychiatric states such as depression and anxiety?
3.	Does the neural mechanism of communication between limbic cortex and the LHb change over time, and does this communication become altered in neuropsychiatric conditions?
4.	What are the cellular and network mechanisms by which the LHb integrates context memory (e.g., from mPFC and hippocampus) and motivational information related to emotional state? Future studies focused on the synaptic basis of memory formation and stress dysregulation of synaptic plasticity at these specific synaptic inputs to LHb are also warranted.
5.	It is well documented that sleep is essential for normal memory and emotion regulation. The strong anatomical connection between the suprachiasmatic nucleus and the LHb, and functional ties between the hippocampus and LHb, suggest that at least part of a memory influence of the LHb may be related to its processing during sleep. This is an understudied area of LHb function.
6.	LHb theories postulate that LHb output guides response flexibility and behavioral adaptation. The mechanisms involved in such behavioral guidance, however, are not clear, nor are the details by which stress might modify these output messages.
7.	Often memory disruption is thought to be the consequence of a disordered behavioral state such as that observed after stress. It is possible, however, that a memory disruption could lead to a stressed state. Distinguishing these interpretations is important yet challenging given the dynamic nature of neural systems.
8.	Are there differential impacts of maternal separation (predictable stress) and single maternal deprivation (unpredictable stress) when it comes to resistance or vulnerability to addictive behaviors, depression and other mood phenotypes?
9.	What are the critical neuromodulations within LHb that could underly anhedonia, motivational deficits, and drug seeking behaviors?