Emotion

PSB 5341

Systems & Behavioral Neuroscience

General Issues• Definition

– Emotion, feelings, affect, mood

• Human construct - animal models– Reductionism

• Natural-kind view– Primaries, separate neural circuitry– Research inconsistencies in humans

• Measurement• Importance

– Spice to life– Communication– Mental disorders associated with mood problems

Importance

• Emotional intelligence: “ability to monitor one’s own and others’ feelings, to discriminate among them, and to use this information to guide one’s thinking and action.”

– Perceiving emotions: detect & identify– Using emotions: to facilitate cognitive task– Understanding emotions: comprehend

emotion language & complicated relationships among emotions

– Managing emotions: regulate emotions in ourselves & others

Physiological Reactions• Somatomotor

– Motor neurons to face– Motor to body

• Visceral– ANS

• Vascular– Cortisol

• Brain– Limbic system

Visceral motor system• All or nothing?

– SNS, Walter Cannon

• Emotion specific patterns– Subjects given muscle-by-muscle instructions for

anger, disgust, fear, happiness, etc– Specific visceral motor pattern (HR, skin temp,

skin conductance)– Strongest when emotional expression

accompanied by subjective experience of emotion– One interpretation: when voluntary facial

expression produced, engage central motor system, but also circuits that underlie emotion

– Source: sensory feedback from muscles & organs; complex eliciting stimulus

Phillip Bard experiments, circa 1928

• Hypothalamus critical for coordination of visceral & motor responses to emotion

• Cats, removed cortex, underlying white matter, basal ganglia

• Sham rage. Acted enraged spontaneously. Also, increased BP, HR, dilation of pupils, hair erection on back & tail. No obvious target (i.e., sham rage)

• Complete response only when caudal hypothalamus intact

Midsaggital view of cat’s brain

(A) Transection through midbrain disconnecting hypothalamus and brainstem abolishes “sham rage.”

(B) Integrated emotional responses of “sham rage” survive so long as caudal hypothalamus remains intact

Walter Hess, Nobel Prize in Physiology & Medicine, 1949.

Electrical stimulation in cats elicited rage response

Descending control of emotional expression:

2 parallel systems anatomically & functionally distinct

Voluntary motor component (classical motor areas in posterior frontal lobe & related circuitry in basal ganglia & cerebellum)

Non-volitional component (cortical & subcortical structures - medial frontal lobe, ventral forebrain including ventral basal ganglia & hypothalamus)

G. -B. Duchenne de Boulogne, Fr. neurologist & physiologist, circa 1862

• Examined small groups of muscles; riches of facial expression• Pioneered use of trans-cutaneous electrical stimulation, then

called “faradization” (after Michael Faraday) to stimulate single & groups of facial muscles;

• Also photographed faces (new technological advance)• obicularis oculi cannot be contracted voluntarily, but are only

“put into play by the sweet emotion of the soul”• Contraction of obicularis oculi surrounding the eyes plus

contraction of zygomaticus major convey the genuine expression of happiness, joy, laughter = “Duchenne smile”

G. -B. Duchenne de Boulogne, Fr. neurologist & physiologist, circa 1862

Subject: Parisian shoemaker

1. Bilateral electrical stimulation of zygomaticus major

2. Closer examination absence of contraction of obicularis oculi

3. Stimulation of brow & neck = terror mixed with pain

4. Subject reported no discomfort or emotional experience with evoked contractions

Person on left: lesion destroyed descending fibers from right motor cortex. Facial paresis. Top: Unable to contract muscle on left side of mouth voluntarily. Bottom: Relative symmetrical smile to humor.

Person on right: Lesion of left forebrain, destroyed descending fibers from nonclassical motor cortical areas. Emotional facial paresis. Top: relatively symmetrical voluntary smile. Bottom: asymmetrical smile to humor.

Deficits explained by selective lesions of one of two anatomically distinct sets of descending projections that influence muscles of facial expression.

Limbic System

• James Papez, circa 1937, 1st proposed specific brain circuit for emotional experience & expression– Focused on medial aspects of the cerebral hemisphere– Limbic lobe; (limulus is Latin for rim); part of cortex that

forms a rim around the corpus callosum & diencephalon– Two main parts: cingulate gyrus & parahippocampal gyrus– Showed that cingulate cortex & hypothalamus

interconnected via anterior n. of dorsal thalamus to cingulate gyrus; cingulate projects to hippocampus; showed hippocampus interconnected with hypothalamus via fornix

– This became Papez’s circuit

Modern Conception of Limbic System

1. Addition of orbital and medial prefrontal cortex. These 2 regions + related structures in thalamus, hypothalamus, and ventral striatus especially important (shown in Green).

2. Other parts of the limbic system, including the hippocampus and mammilary bodies of the hypothalamus, are no longer as strongly linked for processing emotion (shown in blue).

Amygdala

1. Large area in temporal lobe anterior to hippocampus

2. Heinrich Kluver & Paul Bucy; lesion experiments in rhesus monkeys

3. Kluver-Bucy syndrome: visual agnosia, not blind, but responded inappropriately to objects. Bizarre oral behaviors. Hyperactivity. Hypersexual. Change in emotion. Lost hostility & fear to humans. Tame

4. Experimenting with mescaline, gave it to monkeys; experienced paraesthesias in lips; licked, bit & chewed their lips. Explore why. Did sensory & motor lesions without effect. Lip smacking looked similar to patients with temporal lobe epilepsy. So lesioned uncus.

5. First female rhesus monkey, older, extremely vicious, danger to be near her

Amygdala

1. Large area in temporal lobe anterior to hippocampus

2. Consists of multiple, distinct subnuclei; consists of three major & functional divisions, each with unique connections

3. Medial group; extensive connections with olfactory bulb & cortex

4. Basal-lateral group: connections with cerebral cortex, especially orbital & medial prefrontal cortex & association cortex of anterior temporal lobe

5. Central & anterior group: connections with hypothalamus & brainstem, including visceral sensory structures in the nucleus of the solitary tract & parabrachial nucleus.

Amygdala (especially basal-lateral group, participates in triangular circuit linking amygdala, mediodoral thalamus & cortex. Allow interactions between amygdala & prefrontal cortex, as well as indirect modulation of circuitry in ventral basal ganglia.

Pathways of rat brain that mediate the association of auditory & aversive somatic sensory stimuli. Conditioned fear

Model of associative learning in amygdala relevant to emotional function.

Most sensory inputs project to principal neurons of the amygdala

Simultaneous activation of multiple sensory inputs get associated and strengthen synapnatic linkages

Output of amygdala then informs a variety of integrative centers responsible for somatic & visceral motor expression.

Fear & the human amygdala: A case study

1. Patient S.M., suffers from rare autosomal recessive condition, Urbach-Weber disease. Bilateral calcification & atrophy of the anterior-medial temporal lobe; damage to amygdala, but little to hippocampus

2. No deficits in motor, sensory, language, memory, intelligence

3. Deficit in rating intensity of photographs of facial expression, particularly in fearful facial expressions

Top: MRI of brain damage

Patient S.M. asked to draw facial expressions of the same set emotions from memory.

S.M. had artistic experience and produced skillful pictures of each emotion, except for fear.

At first, could not produce a picture for fear & stated that “she did not know what an afraid face would like like.” After several attempts, she produced the sketch on the lower right.

In sum, S.M. has a severely limited concept of fear. Limits ability to experience fear in situations where this emotion is appropriate.

Brain imaging of person suffering from affective (mood disorder). This person has unipolar depression.

See abnormal patterns of blood flow in “triangular” circuit involving amygdala, mediodorsal n. of the thalamus, and the orbital & medial prefrontal cortex.

Feldman Barrett, L. Are emotions natural kinds? Perspectives Psychol. Sci. 1: 28-58, 2006

MRI activity when judging the trustworthiness of human faces

Neural activity in the amygdala is specifically increased, especially when the face in question is considered untrustworthy.

Also see an increase in right insular cortex

Cortical lateralization of emotion

• R. Hemisphere better for expression & comprehension of affective aspects of speech

• Damage to right posterior frontal & anterior parietal lobes - lose ability to express emotion by modulation of speech patterns. Tend to speak in monotone regardless of the circumstance.

• L. hemisphere more important for positive, and r. hemisphere for negative emotions.– Higher incidence of depression with lesions to L. hemisphere

– Increased cheerfulness after lesions to R. hemisphere

• Auditory studies. R. hemisphere better in detecting the emotional nuances of speech

• Facial expressions more accurately identified when presented to left visual field

Kinematic studies of facial expression show that most individuals more quickly and fully express emotion with left facial musculature than with the right.

At right, asymmetrical smiles on some famous faces