Peter G. Fedor-Freybergh

Melatonin, consciousness, and traumatic stress

Abstract:  Descartes intuitively anticipated the so‐called ‘binding problem’ of consciousness and thought that the pineal gland enables spatio‐temporal integration in cognitive processing. Recent findings indicate that a major role in the process of temporal integration and binding involve neurons in suprachiasmatic nuclei, specifically targeting the pineal gland and other structures, and control the neuroendocrine rhythms. Melatonin is an endocrine output signal of the clock and provides circadian information as an endogenous synchronizer which stabilizes and reinforces circadian rhythms. This integrative process occurs at the different levels of the circadian network via gene expression in some brain regions and peripheral structures that enables integration of circadian, hormonal, and metabolic information and creating temporal order of bodily and mental experience. This specific temporal order is reflected in associative sequentiality that is necessary for cognition, behavior and all processes of memory consolidation that must preserve all information in the temporal causal order and synchrony. In this context, recent findings suggest that melatonin could be a potential regulator in the processes that contribute to memory formation, long‐term potentiation, and synaptic plasticity in the hippocampus and other brain regions. There is evidence that stress disrupts normal activity and memory consolidation in the hippocampus and prefrontal cortex, and this process leads to memories that are stored without a contextual or spatiotemporal frame. These findings emphasize a specific role of melatonin in mechanisms of consciousness, memory and stress and are also consistent with reported studies that indicate melatonin alterations under stressful conditions and in mental disorders.

Neuroendocrine response to traumatic dissociation in patients with unipolar depression

Background Dissociation is traditionally attributed to trauma and other psychological stress that are linked to dissociated traumatic memories. Although recent studies regarding neuroendocrinology of traumatic dissociation are rare, they suggest possible dysregulation of the hypothalamus-pituitary-adrenal (HPA) axis. The aim of the present study is to perform examination of HPA axis functioning indexed by basal prolactin and cortisol and test their relationship to psychic and somatoform dissociative symptoms. Design Clinical and laboratory study of consecutive inpatients. Setting Patients treated at the university hospital, Psychiatry department of Charles University in Prague. Participants 40 consecutive inpatients with diagnosis of unipolar depression mean age 43.37 (SD=12.21). Main outcome measures Assessment of psychic and somatoform dissociation (DES, SDQ-20), depressive symptoms (BDI-II) and basal serum prolactin and cortisol. Results Data show that prolactin and cortisol as indices of HPA axis functioning manifest significant relationship to dissociative symptoms. Main results represent highly significant correlations between psychic dissociative symptoms (DES) and serum prolactin (r=0.55, p=0.0001), and relationship between somatoform dissociation (SDQ-20) and serum cortisol (r=-0.38, p=0.008). Conclusions These results indicate relationship between HPA-axis reactivity and psychosocial stress as a function of dissociative symptoms in unipolar depressive patients that could reflect passive coping behavior and disengagement.