Effect of one week of stress on emotional reactivity and learning and memory performances in Japanese quail

Chronic stress is known to induce long term alterations of emotional behaviours as well as cognitive performances leading thereby to welfare or husbandry problems. These stress-induced consequences are observed following long periods of stress lasting from several weeks to several years. The current study examined whether a shorter period of stress (one week) produced similar impairing effects. Two-week old Japanese quail were either submitted to a series of aversive events over consecutive 8 days, at unpredictable times each day (treated animals) or left undisturbed (controls). Following the treatment period, animals were weighed and basal as well as aversive events-induced levels of plasma corticosterone were quantified. Quail were also tested for emotional reactivity in three tests (the tonic immobility test, the hole-in-the-wall and novel object tests) and for spatial reference memory. Although there was no difference in corticosterone levels between the two groups, the treated animals had lower body weight than controls. Behavioural investigations after the treatment period did not reveal any difference between the groups in the three emotional reactivity tests. In the spatial task, treated quail displayed enhanced behavioural flexibility as revealed by their higher performances during the reversal phase of the task. The alteration of growth suggests that a short period of repetitive exposures to unpredictable aversive events can be perceived by quail as stressful. Such a stress period can improve spatial learning performances in quail supporting the critical role played by the duration of the stress period on cognitive performance.

Research highlights▶ A sub-chronic stress period induces a specific physiological and behavioural profile. ▶ In birds, a 8-day long exposure to stressors had no major impact on emotional reactivity. ▶ A 8-day long exposure to stressors did not affect corticosterone levels. ▶ One week of stress improved behavioural flexibility (i.e. reversal learning).