Stereotactic operation in behaviour disorders. Amygdalotomy and hypothalamotomy

Understanding the Role of Oxidative Stress, Neuroinflammation and Abnormal Myelination in Excessive Aggression Associated with Depression: Recent Input from Mechanistic Studies

Aggression and deficient cognitive control problems are widespread in psychiatric disorders, including major depressive disorder (MDD). These abnormalities are known to contribute significantly to the accompanying functional impairment and the global burden of disease. Progress in the development of targeted treatments of excessive aggression and accompanying symptoms has been limited, and there exists a major unmet need to develop more efficacious treatments for depressed patients. Due to the complex nature and the clinical heterogeneity of MDD and the lack of precise knowledge regarding its pathophysiology, effective management is challenging. Nonetheless, the aetiology and pathophysiology of MDD has been the subject of extensive research and there is a vast body of the latest literature that points to new mechanisms for this disorder. Here, we overview the key mechanisms, which include neuroinflammation, oxidative stress, insulin receptor signalling and abnormal myelination. We discuss the hypotheses that have been proposed to unify these processes, as many of these pathways are integrated for the neurobiology of MDD. We also describe the current translational approaches in modelling depression, including the recent advances in stress models of MDD, and emerging novel therapies, including novel approaches to management of excessive aggression, such as anti-diabetic drugs, antioxidant treatment and herbal compositions.

Amygdala and Hypothalamus: Historical Overview With Focus on Aggression

Aggressiveness has a high prevalence in psychiatric patients and is a major health problem. Two brain areas involved in the neural network of aggressive behavior are the amygdala and the hypothalamus. While pharmacological treatments are effective in most patients, some do not properly respond to conventional therapies and are considered medically refractory. In this population, surgical procedures (ie, stereotactic lesions and deep brain stimulation) have been performed in an attempt to improve symptomatology and quality of life. Clinical results obtained after surgery are difficult to interpret, and the mechanisms responsible for postoperative reductions in aggressive behavior are unknown. We review the rationale and neurobiological characteristics that may help to explain why functional neurosurgery has been proposed to control aggressive behavior.

Of Fighting Flies, Mice, and Men: Are Some of the Molecular and Neuronal Mechanisms of Aggression Universal in the Animal Kingdom?

Aggressive behavior is widespread in the animal kingdom, but the degree of molecular conservation between distantly related species is still unclear. Recent reports suggest that at least some of the molecular mechanisms underlying this complex behavior in flies show remarkable similarities with such mechanisms in mice and even humans. Surprisingly, some aspects of neuronal control of aggression also show remarkable similarity between these distantly related species. We will review these recent findings, address the evolutionary implications, and discuss the potential impact for our understanding of human diseases characterized by excessive aggression.

Genetics of aggression in voles

Prairie voles (Microtus ochrogaster) are socially monogamous rodents that form pair bonds-a behavior composed of several social interactions including attachment with a familiar mate and aggression toward conspecific strangers. Therefore, this species has provided an excellent opportunity for the study of pair bonding behavior and its underlying neural mechanisms. In this chapter, we discuss the utility of this unique animal model in the study of aggression and review recent findings illustrating the neurochemical mechanisms underlying pair bonding-induced aggression. Implications of this research for our understanding of the neurobiology of human violence are also discussed.

Interaction between trait anxiety and trait anger predict amygdala reactivity to angry facial expressions in men but not women

The amygdala is critically involved in mediating physiological and behavioral responses to threat. In particular, neuroimaging research indicates that the amygdala is highly responsive to facial signals of threat such as fearful and angry expressions. However, individuals differ substantially in both their relative sensitivity to threat and the magnitude of amygdala reactivity to facial signals of threat. Here, we report the novel finding that individual differences in trait anger are positively correlated with bilateral dorsal amygdala reactivity to angry facial expressions, but only among men with elevated trait anxiety scores. These findings add to the growing body of evidence indicating that variability in personality traits contribute to individual differences in threat-related amygdala reactivity and further suggest that heightened amygdala reactivity to angry faces may be uniquely involved in the expression of reactive aggression in men.

Environmental influences on neural plasticity, the limbic system, emotional development and attachment: a review

The effects of early environmental influences on neural plasticity, the limbic system, and social and emotional development are reviewed and an illustrative case study is briefly discussed. Deprived or abnormal rearing conditions induce severe disturbance in all aspects of social and emotional functioning, and effect the growth and survival of dendrites, axons, synapses, interneurons, neurons, and glia. The amygdala, cingulate, and septal nuclei develop at different rates which correlate with the emergence of wariness, fear, selective attachments, play behavior, and the oral and phallic stages of development. These immature limbic nuclei are "experience-expectant," and may be differentially injured depending on the age at which they suffer deprivation. The medial amygdala and later the cingulate and septal nuclei are the most vulnerable during the first three years of life. If denied sufficient stimulation these nuclei may atrophy, develop seizure-like activity or maintain or form abnormal synaptic interconnections, resulting in social withdrawal, pathological shyness, explosive and inappropriate emotionality, and an inability to form normal emotional attachments.