The Integrative Role of the Sigh in Psychology, Physiology, Pathology, and Neurobiology

Abstract

“Sighs, tears, grief, distress” expresses Johann Sebastian Bach in a musical example for the relationship between sighs and deep emotions. This review explores the neurobiological basis of the sigh and its relationship with psychology, physiology, and pathology. Sighs monitor changes in brain states, induce arousal, and reset breathing variability. These behavioral roles homeostatically regulate breathing stability under physiological and pathological conditions. Sighs evoked in hypoxia evoke arousal and thereby become critical for survival. Hypoarousal and failure to sigh have been associated with sudden infant death syndrome. Increased breathing irregularity may provoke excessive sighing and hyperarousal, a behavioral sequence that may play a role in panic disorders. Essential for generating sighs and breathing is the pre-Bötzinger complex. Modulatory and synaptic interactions within this local network and between networks located in the brainstem, cerebellum, cortex, hypothalamus, amygdala, and the periaqueductal gray may govern the relationships between physiology, psychology, and pathology. Unraveling these circuits will lead to a better understanding of how we balance emotions and how emotions become pathological.

Limbic modulation of the autonomic nervous system

“…Consistent with this, the data presented in Chapter 3 demonstrate modulation of respiratory function by the ventral hippocampus, suggesting that the ventral hippocampus may play a role in the physiological changes required to cope when transiting from one emotional state to another, a factor proposed to affect the expression of augmented breaths (Ramirez, 2014). It is, therefore, possible that the hippocampus may affect the occurrence or phase timing of augmented breaths since there appears to be a coupling of the cardiovascular and respiratory system, particularly during augmented breaths (Marshall and Metcalfe, 1988).…”

“…There are strong correlations between the expression of emotional behaviours such as anxiety and the occurrence of augmented breaths (Soltysik and Jelen, 2005;Wuyts et al, 2011;Vlemincx et al, 2013;Ramirez, 2014). Lesion studies in rats have showed that the ventral hippocampus is a principal limbic structure involved in expressing emotions of fear and anxiety (Bannerman et al, 2003).…”

“…PreBötC activity is in part modulated by commands from the limbic system through the periaqueductal gray (PAG) particularly during the expression of emotional behaviours (Subramanian and Holstege, 2013;Ramirez, 2014). This modulatory effect has been reported to change preBötC neural activity and the respiratory patterning, especially inspiratory control, regulated by the preBötC (Subramanian and Holstege, 2013).…”

Neural Control of Respiration by the Retrotrapezoid Nucleus.

“…Sigh-like events are elicited by hypoxia in brain slices (Lieske et al, 2000;Ramirez, 2014) but, in unaesthetized rats subjected to CBD, hypoxia no longer triggers sighs. The latter in vivo findings argue against a role of CNS hypoxia in triggering sighs but the interpretation of these findings is predicated on the assumption that, in unanesthetized animals exposed to a given low FiO 2 , brainstem parenchymal PO 2 is necessarily lower after CBD than in intact animals.…”

“…Sighs (augmented breaths) may result from a brief reconfiguration of the preBötzinger complex circuitry (Lieske et al, 2000;Ramirez, 2014). Sigh incidence is markedly increased by hypoxia.…”