Hierarchical control systems for the regulation of physiological homeostasis and affect: Can their interactions modulate mood and anhedonia?

Abstract

Predominant concepts assert that conscious willful processes do not assert a significant influence on autonomic functions associated with physiological homeostasis (e.g., thermal regulation). The singular purpose of this review is to promote a reappraisal of concepts regarding the circumscribed role of hierarchical control systems. To effect this reappraisal, we assess the interaction between top-down and bottom-up regulatory mechanisms, specifically by highlighting the intersection between the "physiological" (specifically thermoregulatory pathways) and the "psychological" (specifically mood/anhedonia related processes). This reappraisal suggests that the physiological and psychological processes can interact in unanticipated ways, and is grounded in multiple lines of recent experimental evidence. For example, behavioral techniques that through a combination of hormesis (forced breathing, cold exposure) and meditation appear to exert unusual effects on homeostatic function (cold tolerance) and suppression of aberrant auto-immune responses. The molecular correlates of these effects (the putative release of endogenous cannabinoids and endorphins) may exert salutary effects on mood/anhedonia, even more significant than those exerted by cognitive behavioral techniques or meditation alone. By focusing on this interaction, we present a putative mechanistic model linking physiology with psychology, with particular implications for disturbances of mood/anhedonia. We suggest that volitional changes in breathing patterns can activate primary control centers for descending pain/cold stimuli in periaqueductal gray, initiating a stress-induced analgesic response mediated by endocannabinoid/endorphin release. The analgesic effects, and the feelings of euphoria generated by endocannbinoid release are prolonged via a top-down "outcome expectancy" control mechanism regulated by cortical areas. By focusing on modification strategies that principally target homeostatic function (but may also exert ancillary effects on mood), we articulate a novel framework for how hierarchical control systems for the regulation of physiological homeostasis and affect interact. This interaction may allow practitioners of focused modification strategies to assert increased control over key components of the affective system, allowing for viable treatment approaches for patients with disturbances of mood/anhedonia.