POWERPOINT® SEMINAR SLIDE PRESENTATION PREPARED BY DR. ANWAR HASAN SIDDIQUI, senior resident, dep't of physiology, jnmc, amu, aligarh

©Dr. Anwar Siddiqui

Physiology of Emotion

History

• Aristotle: People are THINKING ANIMAL.What makes peoplr special 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 frightened(Affect)

Must run to safety(conation)

Roaring of lion(stimulus)

• 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

James-Lange theory

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

Cannon-Bard Theory

Schachter-Singer theory

• 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.

Schachter-Singer theory

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

Limbic system

From Arthur C Gyuton Physiology

Limbic system

Connections of limbic system

Papez circuit

• Described by James Papez in 1937.• Papez Proposed that there is an

emotion system that links the cortex to the hypothalamus.

• Discovered the circuit after injecting rabies virus into a cat's 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

Amygdala

• Buried within the anterior-inferior temporal lobe.

• Essential in the control of love, friendliness, affection, fear, rage, aggression

Amygdala Connections

Amygdala connections

Amygdala nuclei

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

Effect of amygdala

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 of Phineus 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 brain's 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 punishm

ent

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 punishm

ent

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 punishm

ent

• 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 punishm

ent

• 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

Neurotransm

itter involved

in reward system

• 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.

Neurotransm

itter involved

in reward system

• Drugs that block postsynaptic D3 dopaminergic receptors such as chlorpromazine hydrochloride lower activity in catecholamine pathways and decrease self stimulation.

Self stimulation rew

ard pathw

ay

dopamine

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.

Physiology of addiction

Physiology of addiction

• A presentation by Dr Anwar H Siddiqui