The Human Brain : From Neurone to Nervous System

THE LIMBIC SYSTEM and EMOTION


  1. Emotions are associated with physical changes, including facial expression, and more generalised changes mediated by the autonomic nervous system and endocrine system.

  2. Extremes of emotion can affect people adversely: excessive sadness can result in depression, or persistent anger can result in uncontrolled aggression; excessive fearfulness can cause anxiety states or panic attacks, while pleasure-seeking can lead to addiction.

  3. All of these situations indicate some imbalance between emotional activity and the consciousness, attention to the outside world. The limbic system consists of areas of cerebral cortex connected to areas of the brain associated with the physical expression of emotion. These areas include the cingulate gyrus, the hippocampus and hypothalamus, which mediate autonomic and hormonal changes; and the amygdala, which is involved in facial recognition, including emotions, and mood.

  4. The limbic cortex consists of a C-shaped ring of cortex on the medial side of each hemisphere, consisting of the cingulate gyrus and the para-hippocampal and dentate gyri on the medial side of the temporal lobe. These areas of the cortex are concerned with the awareness of the context in which emotions are triggered, and are connected to the temporal lobe through a sub-cortical band of association fibres called the cingulum.

  5. Parts of the temporal lobe (hippocampus and amygdala) that deal with memories and emotions and are connected to the hypothalamus using two bands of nerve fibres. The hippocampus and the mamillary bodies of the hypothalamus are connected by the fornix, and the stria terminalis is a smaller bundle of axons that connects the amygdala and the anterior hypothalamic nuclei.

  6. Electrical stimulation of limbic system can induce emotional experiences and autonomic responses, changes in mood and recall of memories.

  7. Key Words: Orbital and Cingulate Cortex, Cingulum, Hippocampus, Amygdala, Fornix, Mamillary Bodies, Striae Terminalis and Septal Area of the Hypothalamus; Emotional Behaviour; Memory, Mood.





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