Lateralization of autonomic activity in response to limb-specific threat

In times of stress or danger, the autonomic nervous system (ANS) signals the fight or flight response. A canonical function of ANS activity is to globally mobilize metabolic resources, preparing the organism to respond to threat. Yet a body of research has demonstrated that, rather than displaying a homogenous pattern across the body, autonomic responses to arousing events - as measured through changes in electrodermal activity (EDA) - can differ between right and left body locations. Surprisingly, the metabolic function of such ANS asymmetry has not been investigated. In the current study, we investigated whether asymmetric autonomic responses could be induced through limb-specific aversive stimulation. Participants were given mild electric stimulation to either the left or right arm while EDA was monitored bilaterally. Across participants, a strong ipsilateral EDA response bias was observed, with increased EDA response in the hand adjacent to the stimulation. This effect was observable in over 50% of individual subjects. These results demonstrate that autonomic output is more complex than canonical interpretations suggest. We suggest that, in stressful situations, autonomic outputs can prepare either the whole-body fight or flight response, or a simply a limb-localized flick, which can effectively neutralize the threat while minimizing global resource consumption. These findings provide insight into the evolutionary pathway of neural systems processing general arousal by linking observed asymmetry in the peripheral arousal response to a historical leveraging of neural structures organized to mediate responses to localized threat.

Mécanismes sous-jacents à la fatigue chronique, un symptôme trop souvent négligé

L’activation de l’hypothalamus par des signaux inflammatoires et/ou de stress peut déclencher celle de l’axe HPA (hypothalamic-pituitary-adrenal axis), qui intègre l’hypothalamus, l’hypophyse et la glande surrénale. L’activation aiguë de l’axe HPA est fondamentale pour la réponse fight or flight (« combats ou fuis »). Elle permet de mobiliser un maximum d’énergie pour un effort, tout en effaçant la fatigue. En revanche, son activation chronique diminue l’efficacité musculaire et entraîne une fatigue chronique. On discutera dans cette partie de plusieurs points stratégiques à considérer pour tenter de comprendre et de traiter ensemble inflammation et fatigue chroniques.

Comparison of Behavioral Cerebral Systems in Tattooed and Non-tattooed Substance-Dependent Individuals

Background: Tattoos or stencils on the body have a special charm for the people of different cultures. The fact that such stencils are considered attractive and essential to some people from a specific culture has led to the conclusion that there might be factors which make tattooing attractive to someone. Objectives: The present study aimed to determine and compare behavioral activation system (BAS), behavioral inhibition system (BIS), and fight-or-flight system between tattooed and non-tattooed substance-dependent individuals. Methods: Using convenience sampling method, this study included 146 substance-dependent individuals (73 tattooed and 73 non-tattooed) referring to Baharan rehabilitation center in Zahedan, Iran. Data collection was done by the short form of the Gray–Wilson Personality Questionnaire (GWPQ), and data were analyzed by independent t-test. Results: According to the results of GWPQ, in BIS, in tattooed individuals, extinction and total scores of avoidance was higher than non-tattooed. Meanwhile, there was no significant difference between BAS and fight-or-flight system. Conclusions: While BAS is associated with positive emotions, BIS is associated with negative emotions. The attitudes of substance-dependent individuals towards tattoos are slightly different from other people. The tattoo can be used as a way to extinction the emotions and avoiding to deal with pejorative emotions. Higher impulsivity can lead substance-dependent people to do high-risk behaviors such as tattooing.

β-adrenergic stimulation synchronizes a broad spectrum of action potential firing rates of cardiac pacemaker cells towards a higher population average

The heartbeat is initiated by pacemaker cells residing in the sinoatrial node (SAN). SAN cells generate spontaneous action potentials (APs), i.e. normal automaticity. The sympathetic nervous system increases heart rate commensurate with blood supply and cardiac output demand, known as the fight-or-flight response, via stimulation of SAN β-adrenergic receptors (βAR). It is classically believed that all cells increase their spontaneous AP firing rate in a similar fashion. In the present study we measured βAR responses among 166 single SAN cells isolated from 33 guinea pig hearts. However, the responses substantially varied. In each cell changes in AP cycle length in response to βAR stimulation highly correlated (R2=0.97) with the AP cycle lengths before stimulation. While, as expected, on average the cells increased their pacemaker rate, greater responses were observed in cells with slower basal rates, and vice versa, cells with higher basal rates showed smaller responses, no responses, or even negative responses, i.e. their rate decreased. Thus, βAR stimulation synchronizes operation of the cell population towards a higher average rate, rather than uniformly shifting the rate in each cell, creating a new paradigm of fight-or-flight response among individual pacemaker SAN cells.