The paraventricular nucleus of the thalamus: an integrative node underlying homeostatic behavior

Abstract

Early anatomical evidence suggested that the paraventricular nucleus of the thalamus (PVT) regulates arousal, as well as emotional and motivated behaviors. We discuss recent studies using modern techniques which now confirm and expand the involvement of the rodent PVT in these functions. Despite the emerging notion that the PVT is implicated in various behavioral processes, a recurrent theme is that activity in this brain region depends on internal state information arriving from the hypothalamus and brainstem, and is influenced by prior experience. We propose that the primary function of the PVT is to detect homeostatic challenges by integrating information about prior experiences, competing needs, and internal state to guide adaptive behavioral responses aimed at restoring homeostasis.

Keywords: arousal; goal-directed behavior; homeostasis; internal state; paraventricular thalamus; valence.

Figure 1.. Conceptual model of the PVT’s role in homeostatic regulation.

(a) Homeostatic challenges represent negative (aversive) signals that activate the pPVT, leading to the induction of aroused states via distributed downstream projections. (b) This negative signal is integrated with cognitive signals from the mPFC as well as with internal state information propagated from diverse hypothalamic and brainstem sources. (c) Following integration, the pPVT participates in the coordination of adaptive behavioral responses largely via the NAc and the CeA. (d) Reinstatement of homeostasis is associated with a positive (rewarding) signal that inhibits the pPVT. Although these four processes are depicted sequentially, they are instead likely occurring as sets of parallel processes in adaptation to an ever-changing environment.

Figure 2.. Schematic representation of major hypothalamic (pink), midbrain (blue), and hindbrain (purple) afferents to the rodent PVT (orange).

AHN, anterior hypothalamic nucleus; DMH, dorsomedial hypothalamus; DpMe, deep mesencephalic nucleus; DRN, dorsal raphe nucleus; LC, locus coeruleus; LH, lateral hypothalamus; MPN, medial preoptic nucleus; NTS, nucleus of the solitary tract; PAG, periaqueductal grey; PBN, parabrachial nucleus; PRF, pontine reticular formation; PVN, paraventricular hypothalamus; PVT, paraventricular thalamus; SCN, suprachiasmatic nucleus; SUM, supramammillary nucleus; VMH, ventromedial hypothalamus; VLM, ventrolateral medulla; ZI, zona incerta.