RLN3 and Alzheimer disease: In this regard, the SHS is a major target of studies aimed at understanding the etiology of age- and dementia-related memory decline; and studies in animal models have revealed that the RLN3/NI network shares anatomical similarities with other neuromodulatory networks implicated in the control of memory and arousal, and AD symptoms, such as the serotonergic, cholinergic, and noradrenergic systems [21, 65–70].