Then, half the lambs were shifted to
the large or the small reward (i.e. positive or negative shift respectively), https://www.selleckchem.com/products/MG132.html while the remaining half continued to get the same amount of reward. Thereafter, the lambs previously submitted to a reward change were shifted back to their initial amount of reward (i.e. successive shifts) while the lambs previously maintained on the same amount of reward were subjected to extinction (no reward, thus a negative shift). Behavior, cortisol levels and cardiac activity were analyzed, and the treatments were compared with ANOVAs for mixed models. When the amount of reward delivered was decreased, the lambs showed more locomotor activity and performed the operant task at a higher frequency but less efficiently, and there was
a decrease in the parasympathetic influence on their cardiac activity. These responses were exacerbated when the negative shift followed a positive one. Similar responses were observed under extinction, and these responses were more pronounced when animals were trained with a large amount see more of reward before extinction. In response to a positive shift, we noticed a decrease in the frequency of the attempted operant task; this occurred only when the positive shift followed a negative one. Variations in plasma cortisol were not consistent with changes in the amount of reward. This study shows that lambs evaluate a reward according to their previous experience with that reward. They are able to form expectations, and a discrepancy from these expectations influences emotional responses, especially in the case of a negative shift. Given the appraisal criteria used by lambs and the matching emotions, we can assume that the emotional response to a negative shift expressed by lambs could reflect the despair
caused by frustration. (C) 2010 Elsevier Ltd. All rights reserved.”
“This study compared the daily pattern of free salivary cortisol secretion in winter and in summer between two groups; participants with self-assessed seasonal affective disorder (SAD) and age- and sex-matched healthy controls. Fifty-two participants completed the study with an equal number in each group. The diurnal pattern of cortisol secretion was assessed across two consecutive weekdays in summer, and two in winter, with conditions being counterbalanced. On each study day participants collected multiple saliva samples in the domestic setting PKC412 solubility dmso to capture the cortisol awakening response (CAR) and declining levels across the day. In addition, perceived stress, anxiety, depression, state stress and state arousal were assessed using validated questionnaires. There was no evidence for any seasonal changes in psychological data or cortisol pattern for the healthy control population. In summer, self-assessed SAD and control participants had similar psychological and cortisol profiles. In winter however, SAD participants reported greater depression, stress and anxiety, and lower levels of arousal.