Depression and stress: a biopsychosocial exploration of evolved functions and mechanisms

Depression is a common and debilitating disorder linked to social adversity and stress. There have been many theories suggesting possible evolved functions of depression but few have explored evolved defensive mechanisms for coping with stressful events and how these maybe compromised in human depression. This paper will review some of the current evolutionary theories of depression and explore how major depression can arise when evolved defences to cope with adversity (e.g., fight, flight, disengage, submit and help-seeking) are aroused but blocked, arrested or ineffective. Psychosocial stressors can be seen as both activating,but also as arresting, evolved stress-coping defences leading to chronic states of stress with physiological effects on mood. This paper is set in the context of an evolution informed biopsychosocial approach.     

The role of the amygdala in conditioned flavor preference

Long-Evans rats with control or amygdala lesions were tested in a conditioned flavor preference task. Half of the rats in each lesion group received an unsweetened grape-flavored solution on odd-numbered days and a sweetened cherry-flavored solution on even-numbered days. The remaining rats received a sweetened grape-flavored solution on odd-numbered days and an unsweetened cherry-flavored solution on even-numbered days. The appropriate solution was presented once a day for 15 min to each rat in the homecage. After six days of testing, each rat received unsweetened cherry and grape flavored solutions simultaneously for 15 min daily across four days. When the two unsweetened flavored solutions were presented simultaneously control rats showed a significant preference for the flavor that was sweetened during training compared to the unsweetened solution. However, amygdala-lesioned rats did not show a preference. The data suggest that the amygdala may be critically involved in mediating reward-based conditioned flavor preference.     

Olfactory discrimination of mouse strains (Mus musculus) and major histocompatibility types by humans (Homo sapiens)

A series of experiments revealed that humans can use olfaction to discriminate closely related strains of mice, differing genetically only at the major histocompatibility gene complex (H-2). In Experiment 1, subjects were asked to distinguish between the whole-body odors of live mice. In Experiments 2 and 3, the odor source was mouse fecal pellets, and in Experiments 4 and 5, the odor source was mouse urine.     

Rights and resources

I would like to thank Arthur Kuflik, Alan Nelson, Phil Valera, Michael Fry and other participants at the Ethikon and School of International Relations at USC-sponsored conference of October, 1987 for helpful comments.     

Frequency effects in the processing of lexicalized and novel nominal compounds

The processing of lexicalized and novel noun-noun compounds of high interpretability was investigated. In Experiment 1, the familiarity of the lexicalized compounds had a significant effect on lexical decision times, but no frequency effects were observed for the constituent nouns. In Experiment 2, a frequency effect was found for the first noun of novel compounds, but not for the second noun. This result was replicated in Experiment 3 with different types of nonwords. A negative word frequency effect for the first noun was found in Experiment 4 in which the novel compounds functioned as nonwords. A frequency effect for the first noun was also observed in Experiment 5, in which a semantic classification task was used. Results point to a decomposition second model according to which access is initially based on the whole compound. If this is unsuccessful the compound will be decomposed and the constituent nouns will be processed separately. It is argued that in novel compounds, nouns are processed sequentially, and different orders of processing are discussed.     

Effects of smoking and nicotine on EEG lateralization as a function of personality

The effects of nicotine/smoking on lateralization of the EEG were evaluated in 40 smokers while they responded to a low-stress, visual vigilance task. Smoking a high-nicotine cigarette was associated with a relatively larger increase in right hemisphere EEG arousal in extraverts and Type-A individuals, but with a relatively larger increase in left hemisphere EEG arousal in introverts and Type Bs. These findings suggest that nicotine/smoking may differentially influence the left and right hemispheres and that this interaction may be a function of personality.     

Dimensions of same-gender student-faculty role-model relationships

This study investigated factors important in the establishment of same-gender student-faculty role-model relationships. Subjects were 33 females and 24 male graduate students enrolled in the same academic department who responded anonymously to scales assessing four characteristics of the role model (personal attributes, life-style and values, power and influence, and professional achievement), three parallel areas of perceived similarity between student and role model (personality, attitudes and values, and professional goals), and students' self-esteem and achievement orientation. As predicted, female students rated the role-model relationship as more important to their professional development than did male students and rated the model's personal attributes and the model's life-style and values as more important in selecting a role model. Consistent with recent theoretical views, female and male students rated both the professional skills and the personal characteristics of the faculty role model as important in establishing the role-model relationship. These findings are interpreted within a framework that considers the continuing effect of belief systems about women's and men's roles on the professional development of women.