Monday, November 28, 2011

How not to revert to habit under stress...

A stressful situation can have the effect of making us actually less able to flexibly cope with the issue at hand, because we tend under stress to regress to older habitual responses that may be less appropriate. Observations by Schwabe et al. suggest that we might be able to lessen this behavior by popping an old fashioned pill like propanolol, a β-adrenoceptor antagonist (which has been used for many years by some musicians to quell their performance anxiety). The second abstract below, from Hermans et al. provides a more detailed view of how our brain networks are changing during stress, and how this is attenuated by β-adrenoceptor receptor blockage.
Stress modulates instrumental action in favor of habit processes that encode the association between a response and preceding stimuli and at the expense of goal-directed processes that learn the association between an action and the motivational value of the outcome. Here, we asked whether this stress-induced shift from goal-directed to habit action is dependent on noradrenergic activation and may therefore be blocked by a β-adrenoceptor antagonist. To this end, healthy men and women were administered a placebo or the β-adrenoceptor antagonist propranolol before they underwent a stress or a control procedure. Shortly after the stress or control procedure, participants were trained in two instrumental actions that led to two distinct food outcomes. After training, one of the food outcomes was selectively devalued by feeding participants to satiety with that food. A subsequent extinction test indicated whether instrumental behavior was goal-directed or habitual. As expected, stress after placebo rendered participants' behavior insensitive to the change in the value of the outcome and thus habitual. After propranolol intake, however, stressed participants behaved, same as controls, goal-directed, suggesting that propranolol blocked the stress-induced bias toward habit behavior. Our findings show that the shift from goal-directed to habitual control of instrumental action under stress necessitates noradrenergic activation and could have important clinical implications, particularly for addictive disorders.
And, more detail from Hermans et al., who find in human studies robust stressor-related changes in functional neuronal activity and connectivity within a network of brain areas, which correlate with increased reports of negative emotionality by the participants, as well as with increases of cortisol and alpha amylase in their saliva:
Acute stress shifts the brain into a state that fosters rapid defense mechanisms. Stress-related neuromodulators are thought to trigger this change by altering properties of large-scale neural populations throughout the brain. We investigated this brain-state shift in humans. During exposure to a fear-related acute stressor, responsiveness and interconnectivity within a network including cortical (frontoinsular, dorsal anterior cingulate, inferotemporal, and temporoparietal) and subcortical (amygdala, thalamus, hypothalamus, and midbrain) regions increased as a function of stress response magnitudes. β-adrenergic receptor blockade, but not cortisol synthesis inhibition, diminished this increase. Thus, our findings reveal that noradrenergic activation during acute stress results in prolonged coupling within a distributed network that integrates information exchange between regions involved in autonomic-neuroendocrine control and vigilant attentional reorienting.

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