Lecture 22: Emotion

Skin conductance

• Lie detector (polygraph) test

• Index of sweating measured by electrodes on the palmar surface of the hands/feet

• Fear & anxiety are linked to high arousal states

Functions of Emotions

1. Prepare the body for action

2. Communicate our emotional states to other people

3. Identify favorable and unfavorable outcomes

4. Instantiate healthy behaviors Eating, drinking, sex, caregiving/prosocial

Hypothalamus

Coordinates the peripheral expression of emotional states

The experience of emotion may depend on cerebral cortex, but the expression of emotion depends on the connection between the ____ and brainstem

“Sham rage”

Philip Bard

Removed cerebral hemispheres in cats, which elicited spontaneous rage he termed ‘sham rage’

→ only occurred if hypothalamus was intact

Altered visceral motor component = increased blood pressure and heart rate, pupil dilation, piloerection of hairs

Altered somatic motor component = arched back, extended claws, tail lashing, snarling

Walter Hess

• Electrical stimulation of parts of hypothalamus also leads to rage responses and attack behavior

• Stimulation of other sites of hypothalamus caused defensive posture resembling fear

Reticular formation

The major target involved in:

• Alertness

• Cardiovascular function

• Respiration

• Urination

• Vomiting

• Swallowing

Output to:

• Brainstem and spinal cord

→ Somatic motor

→ Visceral motor

“Pyramidal smile”

Contrived, voluntary smile

→ Motor cortex via pyramidal tract

Duchenne de Boulogne, 1862

“Duchenne smile”

Spontaneous, emotional smile

→ Anterior cingulate via reticular formation + extrapyramidal motor pathway

limbic lobe

Refers to the part of the cerebral cortex that forms a rim around the corpus callosum

Two prominent components:

• Cingulate gyrus

• Parahippocampal gyrus

Papez circuit

cortical control of emotional expression

1. Hippocampal fibers project to the

2. Mammillary bodies of hypothalamus project through the

3. Mammillothalamic tract to the

4. Anterior thalamic nucleus projects to the

5. Cingulate gyrus projects back to the

6. Hippocampal formation projects via

7. Fornix bundle back to the hypothalamus

Klüver–Bucy syndrome

Resulting from bilateral lesions of the medial temporal lobe

→ can be caused by removal of the amygdala alone

Symptoms include: visual agnosia, decreased emotional reactions, dietary changes, hyperorality, and hypersexuality

Visual agnosia

Inability to recognize familiar objects or people

Docility

• Diminished fear responses or reacting with unusually low aggression

• No longer viewed scientist as threatening

Hyperphagia

Overeating

Hyperorality

"an oral tendency, or compulsion to examine objects by mouth"

Hypersexuality

Heightened sex drive or a tendency to seek sexual stimulation from unusual or inappropriate objects

Central Amygdala (CeA)

Connections with hypothalamus and brainstem (expression of emotion)

Medial Amygdala (MeA)

Extensive connections with olfactory bulb and cortex

Basolateral Amygdala (BLA)

Major connections with orbital/medial prefrontal cortex, associational cortex of anterior temporal lobe

→ (sensory convergence, emotional significance)

Amygdala

Evaluates the emotional value of sensory stimuli

Associative learning → association of stimuli with reinforcers

John Downer

→ Produce monkeys with single amygdala with access to only the visual input from ipsilateral eye

• Monkeys that could see only with eye on same side of amygdala lesion

→ Docile similar to Kluver-Bucy syndrome

Monkeys that could see only with eye on side of intact amygdala = reverted back to normal fearful and often aggressive behavior

• Applies only to visual information → (touching induces a full aggressive behavior)

Patient S.M.

Suffers from a rare condition called Urbach-Wiethe disease

→ Bilateral calcification and atrophy of the anterior-medial temporal lobes, including the amygdala

Asked to rate intensity of emotion in photographs

→ Cannot recognize the emotion of fear

No self reports of fear in daily life over 3 months, all other emotions reported

Prefrontal Cortex

Involved in organizing and planning future behaviors

→ The amygdala may provide emotional input for these deliberations

Likely responsible for the highly subjective ‘feelings’ that attend most emotional states

The amygdala and its connections to the here and basal ganglia are likely to influence the selection & initiation of behaviors aimed at obtaining rewards and avoiding punishments

Affective Disorders

Neurobiological disease → genetic disposition and evidence in neuroimaging studies

• Abnormal blood flow in amygdala, and prefrontal cortex

• Correlation between amygdala blood flow and severity of depression

• Depression abated = normal blood flow in prefrontal cortex

Prefrontal Loop

Initiate and terminate cognitive processing

→ Tourette’s, schizophrenia

Limbic Loop

Regulate emotional and motivational behavior

→ depression, anxiety, drug addiction

Nucleus accumbens (NAcc) under modulation from ventral tegmental area (VTA)

Lateralization of Emotions

• Left hemisphere more involved with positive emotions

• Right hemisphere more involved with negative emotions

• Humans more quickly to express positive emotion with left facial muscles (controlled by right hemisphere)

Ventral Tegmental Area (VTA)

These neurons start signaling the presence of the reward-predicting stimulus instead of reward

Learn to fire to cues before the reward

Posttraumatic stress disorder (PTSD)

Symptoms: persistently reexperiencing the traumatic event, avoiding reminders of the event, numbed responsiveness, and heightened arousal

→ Often accompanied by depression & substance abuse, which complicates treatment & recovery

Treatment → Cognitive-behavioral therapies and anti-anxiety/antidepressant medications

• There is no cure

• Can persist for decades

Hippocampus shrinks and SCR magnitude increases