Understanding how discrete populations of hypothalamic neurons orchestrate complicated behavioral states

Abstract

A major question in systems neuroscience is how a single population of neurons can interact with the rest of the brain to orchestrate complex behavioral states. The hypothalamus contains many such discrete neuronal populations that individually regulate arousal, feeding, and drinking. For example, hypothalamic neurons that express hypocretin (Hcrt) neuropeptides can sense homeostatic and metabolic factors affecting wakefulness and orchestrate organismal arousal. Neurons that express agouti-related protein (AgRP) can sense the metabolic needs of the body and orchestrate a state of hunger. The organum vasculosum of the lamina terminalis (OVLT) can detect the hypertonicity of blood and orchestrate a state of thirst. Each hypothalamic population is sufficient to generate complicated behavioral states through the combined efforts of distinct efferent projections. The principal challenge to understanding these brain systems is therefore to determine the individual roles of each downstream projection for each behavioral state. In recent years, the development and application of temporally precise, genetically encoded tools has greatly improved our understanding of the structure and function of these neural systems. This review will survey recent advances in our understanding of how these individual hypothalamic populations can orchestrate complicated behavioral states due to the combined efforts of individual downstream projections.

Neuroendocrine modulation sustains the C. elegans forward motor state

“…In Drosophila larvae, local modulatory neurons in the ventral nerve cord secrete biogenic amines to activate and modify crawling patterns (Selcho et al, 2012). In vertebrates, the hypothalamus produces and releases many hormones to control appetite, reproduction, circadian rhythms, and social behaviors (Graebner et al, 2015; Schwartz et al, 1996; Selcho et al, 2012; Strauss and Meyer, 1962). Similarly, the vertebrate spinal cord locomotory circuits are activated and modified by multiple amines that are secreted by descending neurons at the brainstem, as well as by secretory neurons that reside locally in lower vertebrates such as the lamprey (reviewed in Miles and Sillar, 2011).…”

A tale of two circuits: CCK NTS neuron stimulation controls appetite and induces opposing motivational states by projections to distinct brain regions

“…By manipulating the activity of genetically identified cells within a specific region of the brain in vivo , researchers have uncovered several pathways that are directly involved in an animal’s motivation to eat or not to eat [for reviews see: (Graebner et al, 2015; Krashes and Kravitz, 2014; Sternson and Roth, 2014)]. Recently, we and others have elucidated a role for CCK-expressing neurons in the NTS in the cessation of feeding (D'Agostino et al, 2016; Roman et al, 2016).…”

Memory of recent oxygen experience switches pheromone valence in Caenorhabditis elegans

“…Despite this simplicity, the mechanisms by which its nervous system marshals information about past and present sensory experience to shape behavioral priorities remain largely mysterious. The anatomical connectome, while valuable (22), is insufficient to explain or predict neuronal network function (23,24), partly because neuromodulators can dynamically reconfigure and specify functional circuits (25)(26)(27).…”