There is increasing evidence for an important role of adverse early experience on the development of major psychiatric disorders in adulthood. Corticotropinreleasing factor (CRF), an endogenous neuropeptide, is the primary physiological regulator of the mammalian stress response. Grown nonhuman primates who were exposed as infants to adverse early rearing conditions were studied to determine if long-term alterations of CRF neuronal systems had occurred following the early stressor. In comparison to monkeys reared by mothers foraging under predictable conditions, infant monkeys raised by mothers foraging under unpredictable conditions exhibited persistently elevated cerebrospinal fluid (CSF) concentrations of CRF. Because hyperactivity of CRF-releasing neurons has been implicated in the pathophysiology of certain human affective and anxiety disorders, the present finding provides a potential neurobiological mechanism by which early-life stressors may contribute to adult psychopathology.Considerable evidence from genetic, neurochemical, pharmacological, and neuroanatomical studies obtained over the past three decades supports a biological basis for many of the major neuropsychiatric disorders (1). Prior to the modern era of biological psychiatry, psychoanalytic theory pioneered by Freud prevailed. Freud's theories emphasized the importance of early rearing conflicts in the pathogenesis of adult psychopathology (2). More recent studies indicate that psychosocial factors, including abuse and neglect in early life as well as untoward life events in adulthood, contribute to the development of mood and anxiety disorders (3, 4). An integration of biological and developmental approaches may illuminate further the role of adverse early life experience on subsequent neurodevelopment. Using random-assignment study designs, nonhuman primate models of psychopathology, produced by an unpredictable early rearing environment, provide for the experimental exclusion of genetic influences on development, a strategy rarely feasible in humans (5-9).The present study presents evidence for persistent hyperactivity of corticotropin-releasing factor (CRF)-releasing neurons in the central nervous system (CNS) of grown nonhuman primates who, as infants, were reared by mothers exposed to environmental unpredictability. A neurochemically based hypothesis is proposed whereby emotionally adverse early experiences may antecede psychiatric disorders through the induction of persistently elevated neuronal release of CRF.The CRF-containing parvocellular neurons of the hypothalamic paraventricular nucleus (PVN) represent the cephalicThe publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact. component of the hypothalamic-pituitary-adrenal (HPA) axis, which serves as the primary endocrine response of mammalian organisms to stress (10-12). Hypothalamic CRF release increases HPA axis activity by ...
Research has shown that in conjunction with genetic factors, significant aspects of non‐human primate development are influenced by the infant's physical and social environment. In addition to the direct impact of the environment on the infant, the infant's attachment relationship with the mother is seen as the primary mediating factor in shaping these influences. When the mother is able to cope with environmental demands, as a reflection of her responsivity to her infant's needs, she may prepare infants for periodic interuptions in her attention, ameliorate distress during disruptive periods and, most importantly, compensate for these disruptions with enhanced attention to her infant once they are ended. Our recent work shows that when the mother's survival requirements increase, and her coping capacities are exceeded, both short and long‐term deleterious effects on her developing offspring may emerge. Particularly when confronted with an unpredictable environment, mothers are less able to maintain effective, stress‐buffering, maternal‐coping mechanisms which can preserve a stable attachment relationship and permit normal infant development. When these coping mechanisms are insufficient, infants may show manifest disturbances, such as depression, during development or reveal more latent disturbances, such as reduced sociability and timidity, when psychologically challenged, even as young adults. Evidence now suggests that these long‐term effects may, at least in part, be the product of altered neurodevelopment of the serotonergic and noradrenergic systems.
12 bonnet macaque (Macaca radiata) mother-infant dyads were studied. For 14 weeks, beginning when the infants were a mean age of 11.2 weeks, the dyads were housed and observed under different foraging-demand conditions for the mothers: 6 dyads in a low-foraging-demand (LFD) condition and 6 dyads in a variable-foraging-demand (VFD) conditions. For VFD mothers, demand varied between low and high in 2-week blocks. Differences between the LFD and VFD groups were minimal during this period; there was, however, more maternal grooming and shorter separation bouts in the VFD group than in the LFD group. The dyads were then challenged by brief introductions to a novel environment. The challenge revealed that frequency of breaking dyadic contact and levels of play were significantly lower for the VFD infants than for the LFD infants, perhaps as a consequence of less secure attachment.
A number of studies have now indicated that monkeys of several species will perform hundreds of food-rewarded joystick tasks on a daily basis. Our goal in this study was to identify the level of joystick task performance that could be maintained by 10 sec. of live, color video of a conspecific social group contingent upon the completion of a joystick task. The subjects were five individually housed bonnet macaques that were highly experienced on joystick tasks. Performance with social-video reward was compared to that maintained by a 190-mg banana-flavored pellet reward and to a nonreward condition. Comparable levels of task activity were maintained by both video and pellet reward, whereas task activity nearly ceased in the absence of reward. Four of the five monkeys increased their levels of task activity between the first and second weeks of social-video reward.
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