Transcript 20-Limbic
1 Dr. Vohra Emotional Nervous System 2 Dr. Vohra The main object of primitive life are FOOD & SEX. Food is necessary for survival of individual & sex for the survival of the species. The brain is therefore adapted to control & regulate behavior of the animal through a system called the Limbic System. It is a set of evolutionarily primitive brain structures located on top of the brainstem & buried under the cortex, are involved in many of our emotions & motivations, particularly those that are related to survival. Such emotions include fear, anger, & emotions related to sexual behavior. 3 Dr. Vohra The limbic system earns its name from its position on the medial rim of the brain. Limbic system consists of a number of structures with complex connections which all ultimately project into the hypothalamus. It appears to be primarily responsible for our emotional life, formation of memories & internal homeostasis. 4 Dr. Vohra Controls Emotions Emotional Responses Hormonal Secretions Mood Motivation Pain & Pleasure Sensations The limbic system includes the hypothalamus, the hippocampus, amygdala, Septum and several other nearby areas. Cingulate gyrus Hippocampal formation Amygdala Ventral amygdafugal Stria pathway terminalis Fornix Septum Medial forebrain bundle Hypothalamus & their 6 Principal parts of the limbic systemDr. Vohra relationship with the hypothalamus The powerful input to the limbic system from the neocortex association areas links complex ‘goal directed’ behavior to more primitive instinctual behavior & internal homeostasis in a cascade of neuronal connections. Reception of information from outside world through (e.g. vision, hearing & touch) are refined in the parietal-occipital association areas. This information then conveyed to the frontal association areas involved in planned behavior (regulation) & also to the temporal association areas, where information can reach supramodal status & meaning (sementic processing) 7 Dr. Vohra Entry of the information into the limbic system is either directly, to the amygdala, or indirectly to the hippocampal formation, via entorhinal area. The amygdala appears to provide suggestion to experience & especially relevant to social stimuli. The affect is an evolutionary development from more primitive ‘feelings’, derived from sensory autonomic input bodily organs into the hypothalamus. The information permits a link to previous experience since the hippocampal formation is essential to remembering & learning (memory) 8 Dr. Vohra Hypothalamus is the most ventral part of the diencephalon lying beneath the thalmus. Its functions include homeostasis, emotion, thirst, hunger, circadian rhythms, and control of the autonomic nervous system. In addition, it controls the pituitary a coronal view Circadian rhythms are regular changes in mental and physical characteristics that occur in the course of a day 9 Dr. Vohra Amygdala- lies near the temporal pole, b/w the inferior horn of lateral ventricle & lentiform nucleus. It receives afferents from inferior temporal association cortex the septum & olfactory tract. The principal efferent projection from amygdala is stria terminalis which runs in the wall of the lateral ventricle terminate in the hypothalamus. The ventral amygdofugal path also projects to the hypothalamus. 10 Dr. Vohra Connects with the hippocampus, the septum, the prefrontal area and the thalamus. These connections make it possible for the amygdala to play its important role on the mediation and control of major affective activities like friendship, love and affection, on the expression of mood and, mainly, on fear, anger and violent behavior. The amygdala, being the center for identification of danger. When triggered, it gives rise to fear and anxiety which lead the person into a stage of alertness, getting ready to flight or fight. Damage or destruction of both amygdalas (there are two of them, one in each hemisphere) makes the individual, sexually non-discriminative, and unconcerned to danger. 11 The septum or septal region lies beneath the rostral part of the corpus callosum. Interconnects with the amygdala & projects to the hypothalamus via medial forebrain bundle. Cingulate gyrus Hippocampal formation Septum Amagdala Ventral amygdafugal pathway Fornix Stria terminalis 12 Hypothalamus Medial forebrain bundle Dr. Vohra The total act of copulation is organized in the anterior part of the hypothalamus and the neighboring septal region. In the male, erection of the penis and ejaculation are organized in this area, which is adjacent to the area for urination. Under normal circumstances the neurons that organize mating behavior do so only when they receive relevant hormones in their blood supply. But when the septal region is electrically stimulated in conscious patients, sexual emotions and thoughts are produced. 13 Dr. Vohra Is consists of the hippocampus itself, the dentate gyrus & parts of parahippocampal gyrus. The hippocampus is formed by an infolding of inferomedial part of temporal lobe into the lateral ventricle. The hippocampal formation receives principal afferents from inferior temporal coxtex. The principal efferent from hippocampus is the fornix (C-shaped fascicle of fibres) which links hippocampus with the mammillary body of hypothalamus. Efferent fibers converge on the ventral surface of the hippocampus as fimbria. Dr. Vohra The fimbria passes posteriorly & superiorly to become continuous with the crus of fornix. The two crura unite to form the body of the fornix. Some fibers cross to the opposite side through small hippocampal commissure. The body of the fornix divides into two columns & enter the hypothalamus where the majority of the fibers terminate in the mammillary body. The mammillary body in turn projects to the anterior nuclear group of the thalamus via mammilothalamic tract & to the brainstem via mammillotegmental tract. The anterior nucleus of thalamus has major connections with the cingulate gyrus. 15 Dr. Vohra 16 interconnection of limbic structures Dr. Vohrawhich constitute the Papez circuit The The cingulate gyrus & parahyppocampal gyrus are in continuity with one another around the splenium of the carpus callosum. It provides a pathway from the thalamus to the hippocampus, seems to be responsible for focusing attention on emotionally significant events, and for associating memories to smells and to pain. 17 Dr. Vohra 18 Dr. Vohra Korsakoff’s psychosis is a condition that mainly affects chronic alcoholics. It is due vitamin B deficiency leads to capilary haemorrhages in the upper brain & limbic system. The syndrome is characterized by a severe memory defect, especially for recent event. Psychologists working with these patients often have great problems sorting out what is truth and what is lies of what patients say. Temporal lobe or complex partial seizers arising close to the amygdala & hippocampi can lead to complex experience of smell, mood & memory. Other symptoms may include hallucination, anxiety, fear, depression, confusion, delusions and insomnia; painful extremities, sometimes bilateral wrist drop, more frequent bilateral foot drop with pain or pressure over the long nerves. Surgical ablation of amygdala has removed the uncontrollable anger reactions in some psychotic patients 19 Dr. Vohra 20 Dr. Vohra 21 Dr. Vohra