• Aristotle: People are THINKING ANIMAL.What makes peoplr specialHistory is they can overcome their brutish emotions. • Rousseau: Emotiuons are what makes people special and gives us reason for living. • Hippocrates: Brain is the site of emotion
Introduction • The word emotion is derived from the latin word emovere which means to stir up to get agitated • Complex feeling state with psychic, somatic, autonomic and behavioral components.
• Emotion has two components: – Mental – Physical• Mental component: – Cognition- Awareness of sensation and it’s cause. – Affect- The feeling itself. – Conation- urge to take action.
Oh it’s a roar. The roar seems to be that of lion (Cognition) I feel frightenedRoaring of lion(stimulus) (Affect) Must run to safety (conation)
• Physical components: – Changes in viscera and skeletal muscle – Coordinated activity of autonomic and somatic nervous system – Example: tachycardia, tachypnoea, cutaneous vasoconstriction etc in fear
Theories of emotion • James-Lang theory • Cannon-Bard theory • Schachter-Singer theory. • Current Theory
James lange theory • Developed independently by Williams James and Carl Lange in 1884 • According to the theory an emotional event causes response in ANS. This response is detected by CNS to produce an emotional experience. • Different emotional stimuli produces different bodily response and lead to different emotions
Cannon-Bard Theory • Walter Cannon and Phillip Bard – 1927 • The physiological reaction and the emotion are assumed to occur at the same time. • Emotional stimuli simultaneously produce a response in the ANS and in the cerebral cortex. • The emotional experience is the combination of these two system.
Cannon-Bard Theory • The influence of the cerebral cortex in controlling emotion is show in the phenomenon of Sham rage. • When animals have their cortex removed they go in extreme rages at the slightest provocation. • The response is often unrelated to provocation and is short lived
theorySchachter-Singer • Also called cognitive arousal theory. • A two-stage theory stating that for an emotion to occur, there must be (1) physiological arousal and (2) an explanation for the arousal. • Emotions are produced when autonomic arousal is noticed by the person. He/She tries to come up with an explanation for the arousal and depending on the explanation, label their emotion.
Current Theory • No single neural system produces emotions • Different emotions may depend on different neural circuits, but many of these circuits converge in the same parts of the brain • The limbic system may be involved in some emotional experiences, but it is not the sole neural system underlying emotion • Feelings (emotion) result from the interplay between: – The amygdala, hypothalamus, brain stem & autonomic nervous system.
Limbic system • Limbus means a ring • Limbic system part of cortical and subcortical structure forming a ring around brainstem. • The French physician Paul Broca first called this part of the brain "le grand lobe limbique" in 1878. • Formerly called rhinencephalon. • The components of the limbic system located in the cerebral cortex have fewer layers than the classical 6-layered neocortex, and are classified as allocortex or archicortex.
Limbic system • Consist of limbic lobe and related subcortical nuclei. • Limbic lobe includes – Cingulate gyrus – Isthmus – Hippocampal gyrus – Uncus • Subcortical nuclei include – Amygdala – Septal nuclei – Hypothalamus – Anterior thalamic nuclei
• Described by James Papez in 1937.Papez circuit • Papez Proposed that there is an emotion system that links the cortex to the hypothalamus. • Discovered the circuit after injecting rabies virus into a cats hippocampus and monitoring its progression through the brain. • One of the major pathways of the limbic system and is chiefly involved in the cortical control of emotion.
Papez circuit • The original circuit proposed by Papez is shown by thick lines and more recent connections as proposed by Paul D. MacLean are shown by thin line
• Buried within the anterior-inferior temporal lobe.Amygdala • Essential in the control of love, friendliness, affection, fear, rage, aggression
Amygdala nuclei • Medial nucleus: Sensory input, especially odour, relayed to forebrain and hypothalamus • Central nucleus: Sensory input via cortex and thalamus, relayed to hypothalamus and brainstem nuclei • Basal nucleus: Sensory input relayed to rest of amygdala and to PAG
Central nucleus • Plays the major role in emotional response patterns • Affects hypothalamus and both branches of ANS: Increased HR and BP; ulcers, urination, and defecation • Affects brainstem nuclei to increase arousal (VTA), vigilance (LC), cortex activation (DLTN and nucleus basalis) and startle (pons) • Destruction of central nucleus limits emotional response patterns. • Electrical stimulation of central nucleus triggers fear, agitation, stress illness
Amygdala lesion • Reduced ability to identify motivational and emotional significance of events • Electrical stimulation of amygdala can lead to emotional attacks (rage) Kluver-Bucy Syndrome: • Results from bilateral removal of the amygdala and inferior temporal cortex. Includes: – loss of fear – Indiscriminate dietary behaviour – Greatly increased autoerotic sexual activity – Tendency to attend to every visual stimulus – Tendency to examine all objects by mouth – Visual agnosia (cannot recognize objects visually) – Inability to recognize facial expression
Effect of emotion Autonomic nervous system • In threatening situation sympathetic nervous system releases norepinephrine that causes – Palm sweating – Increased heart rate – Focused attention – Greater skin conductance Immune system • Depressive disorders are associated with decreased lymphocyte production
Effects of emotion Endocrine disturbances • HPA activity: elevated in stress increased in depression • Thyroid axis activity: In depression both hypothyroidism (5-10%) & hyperthyroidism (20-30%) found. Growth hormone: • NE and dopamine stimulates growth hormone secretion whereas somatostatin inhibits it. • Decreased csf somatostatins are found in depression, increased level is seen in mania
Physiology of special emotion Fear • Site: The hypothalamus and amygdaloid nuclei • Effects of lesion: After destruction of amygdala the fear reaction and its autonomic and endocrine manifestation are absent.eg monkeys are normally terrified of snakes but after bilateral lobectomy they approach snake pick them n eat them • In humans amygdala damage causes deficient fear response to visual and auditory stimulus
The classical and curious case ofPhineus Gage.• Phineas P. Gage (July 9, 1823 – May 21, 1860) was an American railroad construction foreman now remembered for his improbable survival of an accident in which a large iron rod was driven completely through his head, destroying much of his brains left frontal lobe.• The damage to Gage’s frontal cortex had resulted in a complete loss of social inhibitions, which often led to inappropriate behaviour. In effect, the tamping iron had performed a frontal lobotomy on Gage, but the exact nature of the damage incurred to his brain has been a subject of debate ever since the accident occurred.
Physiology of special emotion Anxiety: It is normal emotion in appropriate situation but excessive anxiety & anxiety in inappropriate situation is disabling. • Site: associated with bilateral increase in blood flow in discreet portion of anterior end of each temporal lobe. • Facts: Anxiety is relieved by benzodiazepine which binds to GABA receptors and increase conductance of these ion channels.
Physiology of special emotion Rage and placidity: – Rage- extreme form of anger – Placidity- Calm and peaceful • Site: Neocortex, ventromedial hypothalamic nuclei • Facts: Human maintains a balance between rage and placidity. Major irritation make normal individual loose temper but minor stimuli are ignored.
Motivation • Motivation literally means that which moves the will. • It is a factor in most of the behaviour. • Factors that are responsible for goal direction of a behaviour are the motivation for that behaviour.
Reward and punishment Rewards: • Things that an individual work for • They make the behaviours leading to them more often to occur. Punishments: • Opposite of rewards • Associated with avoidance leading to behaviour where an individual tries to escape a painful situation.
Reward and punishment Neural mechanism involved: • The neural mechanism of motivation has ben obtained by studying the effect of brain self stimulation. • An unanaesthetised animal (rat) regulates the rate at which electrical stimuli are delivered through electrode implanted in defined area of limbic system.
Reward and punishment • The brain area where stimulation leads to repeated bar pressing are located in: – The medial fore brain bundle – Midbrain tegmentum – Nucleus accumbens – Dorsal brain stem – Ventral tegmental area • Stimulation of these sites produce pleasurable sensation like relief of tension, relaxed feelings
Reward and punishment • The brain area where stimulation is avoided are: – Lateral portion of posterior hypothalamus – Dorsal midbrain – Entrorhinal cortex • Stimulation of these sites produces sensation ranging from vague fear to terror
in reward systemNeurotransmitter involved • The catecholamines (dopamine and norepinephrine), morphine, enkephalin are involved in the pathways mediating reward system. • Drugs that increase the self stimulation are: – Amphetamine- cause increase release of dopamine – Cocaine- binds and inhibit dopamine transporter-dopamine uptake is reduced- extracellular dopamine level is increased.
in reward systemNeurotransmitter involved • Drugs that block postsynaptic D3 dopaminergic receptors such as chlorpromazine hydrochloride lower activity in catecholamine pathways and decrease self stimulation.
Physiology of addiction • A kind of dependence which manifests as: – compulsive non-medical use of a substance – loss of control over its use despite negative consequences • Despite many differences, virtually all substances with the potential for addiction affect dopamine levels in the pleasure / reward pathway of the brain.