Limbic system Limbic system Means ‘border’ Includes cortical and subcortical structures in the forebrain Seat of emotions and feelings Emotions and feelings Emotional state physical sensation conscious feeling Different regions of brain involved in physical and mental component of emotional state Physiology of Emotions Aroused state have intense feeling, autonomic activation and related behavior Components Mental Physical Mental or sensory component Cognition – aware and recognize the sound Affect – development of feeling (frightening) Conation – force which direct to take action (plan to runaway) Physical component Somatic – changes in skeletal muscle (running away) Autonomic – sympathetic and parasympathetic ( RR) HR, BP, Neural system that control emotions Limbic system Limbic cortex Ring of phylogenetically primitive cortex (paleocortex) Cingulate gyrus – medial aspect of the cerebral hemisphere Parahippocampal gyrus and uncus - ventromedial surface of the temporal lobe Orbitofrontal area on the ventral surface of the frontal lobes Subcallosal gyrus Subcortical limbic areas Amygdala. Hypothalamus Septum Paraolfactory area Anterior nucleus of the thalamus Portions of the basal ganglia Hippocampus Papez circuit Hypothalamus communicates reciprocally with areas of the limbic cortex Conscious and the autonomic components of emotion influence each other Cingulate gyrus Anterior nucleus of thalamus Hippocampus Mammillary body of hypothalamus Papez circuit Hippocampal formation processes information from the cingulate gyrus Conveys it to the mammillary bodies of the hypothalamus by way of the fornix Hypothalamus provides information to the cingulate gyrus by a pathway from the mammillary bodies to the anterior thalamic nuclei (the mammillothalamic tract) From there to the cingulate gyrus Functions of limbic lobe Motivation Addiction Emotions of rage, fear, anxiety, aggression Sexual behavior Autonomic responses Motivation Act that moves the will Reward or punishment affective nature of sensations - whether the sensations are pleasant or unpleasant. Reward and punishment centers in brain identified by experimental studies Skinner box Reward centers Nucleus accumbens Along the medial forebrain bundle – which extends from the septal and orbitofrontal cortex to brain stem Ventromedial and lateral nucleus of hypothalamus Septum amygdala certain areas of the thalamus and basal ganglia Punishment centers Central gray area surrounding the aqueduct of Sylvius in the mesencephalon Periventricular zones of the hypothalamus and thalamus Addiction Compulsion to repeatedly use a substance inspite of knowing negative impact of the substance to health Mechanism – increase in dopamine concentration in reward system Areas: Nucleus accumbens Projections from frontal cortex, amygdala, hippocampus Rage and placidity Rage – anger when person loses temper to minor stimuli Neocortex Ventromedian hypothalamus septum Amygdala Placidity – person not disturbed even to major irritating stimuli Bilateral lesion of amygdala Aggression Violent form of rage Hypothalamus Amygdala Fear Hypothalamus Amygdala Sexual behavior Basic sexual drive is a function of limbic system and hypothalamus and cortex Controlled by neural and endocrinal factors Anxiety Uncertainty about future or apprehension of unknown Frontal part of temporal lobes Benzodiazipines (Anxiolytics)– act by cl- conductance in receptors Autonomic responses to emotions Amygdala Hypothalamus Emotions affect Cardiovascular system Respiratory system GIT Regulation of feeding behavior Hypothalamus Satiety center – ventromedian nucleus Lateral hypothalamus – feeding center Amygdala – movement with eating (chewing, swallowing, licking) Hypothalamus Responsible for the physiological effects of emotions Electrical stimulation in cats of the lateral hypothalamus cause autonomic and somatic responses characteristic of anger increased blood pressure raising of the body hair pupillary constriction arching of the back raising of the tail. (Defensive) Behavioral functions of the hypothalamus Lateral nucleus – appetite and thirst, rage Ventromedial nucleus – satiety, tranquility Periventricular area – fear Sexual drive – most anterior and posterior regions Lesions of the hypothalamus Lesions of lateral nucleus –decreased eating and drinking, passivity Lesions of ventromedial nucleus – excessive drinking and eating, hyperactivity Amygdala Multiple small nuclei located beneath the cerebral cortex of medial anterior pole of each temporal lobe. Has bidirectional connections with the hypothalamus and other areas of the limbic system. Basolateral nuclei – receives afferent information Central nucleus – efferent connections with hypothalamus and brain stem areas Functions of amygdala Electrical stimulation of the amygdala in humans produces feelings of fear and apprehension. Mediates both inborn and acquired emotional responses Responsible for fear conditioning Has a role in the conscious feeling and autonomic manifestations of emotional state Conditioning of fear Hypothalamus – responsible for the somatic expression of emotion Cingulate gyrus and parahippocampal gyrus – conscious feeling Role of the cortex Cingulate gyrus and the prefrontal cortex – conscious experience of the emotion Lesions of the cingulate gyrus or the prefrontal cortex – Pain is perceived and autonomic responses are present Unpleasant experience is absent KluverBucy syndrome When the anterior parts of both temporal lobes are destroyed in a monkey Characteristics of the animal not afraid of anything has extreme curiosity about everything forgets rapidly has a tendency to place everything in its mouth and sometimes even tries to eat solid objects Strong sex drive Neurotransmitters Dopaminergic system (Nucleus accumbens) – motivation and addiction Serotonergic system – mood elevator, suppress sleep Histaminergic system – arousal, sexual behavior, regulation of BP, water intake Cholinergic system – learning, memory, cognition, sleep
