Abstract
The paraventricular thalamic nucleus (PVT) is highly interconnected with brain areas that control reward-seeking behavior. Despite this known connectivity, broad manipulations of PVT often lead to mixed, and even opposing, behavioral effects, clouding our understanding of how PVT precisely contributes to reward processing. Although the function of PVT in influencing reward-seeking is poorly understood, recent studies show that forebrain and hypothalamic inputs to, and nucleus accumbens (NAc) and amygdalar outputs from, PVT are strongly implicated in PVT responses to conditioned and appetitive or aversive stimuli that determine whether an animal will approach or avoid specific rewards. These studies, which have used an array of chemogenetic, optogenetic, and calcium imaging technologies, have shown that activity in PVT input and output circuits is highly heterogeneous, with mixed activity patterns that contribute to behavior in highly distinct manners. Thus, it is important to perform experiments in precisely defined cell types to elucidate how the PVT network contributes to reward-seeking behaviors. In this review, we describe the complex heterogeneity within PVT circuitry that appears to influence the decision to seek or avoid a reward and point out gaps in our understanding that should be investigated in future studies.
Highlights
Several recent reviews have comprehensively summarized the literature on the role of the paraventricular nucleus of the thalamus (PVT) in reward-seeking (James and Dayas, 2013; Kirouac, 2015; Do-Monte and Kirouac, 2017; Millan et al, 2017; Zhou and Zhu, 2019; Matzeu and Martin-Fardon, 2020)
These studies highlight the heterogeneity of PVT neurons based on anatomical location, projection profile, and most notably gene expression— we have barely pierced the surface into understanding the unique cell types that exist in PVT
Using optogenetics we found that inhibitory coding at prefrontal cortex (PFC) inputs was critical for downstream cue-evoked inhibition of select pPVT→nucleus accumbens (NAc) neurons (Otis et al, 2019)
Summary
Several recent reviews have comprehensively summarized the literature on the role of the paraventricular nucleus of the thalamus (PVT) in reward-seeking (James and Dayas, 2013; Kirouac, 2015; Do-Monte and Kirouac, 2017; Millan et al, 2017; Zhou and Zhu, 2019; Matzeu and Martin-Fardon, 2020). Based on a growing body of evidence, a consensus is emerging that PVT is part of a network that mediates appetitive/approach and aversive/avoidance behaviors, during motivational conflicts (Choi and McNally, 2017; Choi et al, 2019). Up until now, efforts to investigate the role of PVT subpopulations based on these criteria in appetitive/approach and aversive/avoidance behaviors have been limited. We point out areas in which conflicting or inconsistent conclusions about PVT functioning may be resolved by combining existing and emerging technology to define the characteristics and function of PVT cell populations
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