Chapter 18: Brain Mechanisms of Emotion

Darwin’s Theory of emotion

all species have shared emotional expression, inherited by common ancestor

James-Lange Theory

body signals (ANS) causes us to experience emotion

ex) mouse hear stimulated through optogenetics → showed anxiety like behaviors

• Papez circuit: body → hypothalamus → cingulate cortex

Cannon-Bard Theory

thalamus → 1) ANS 2) emotional experience

• body feedback contributes but not required for feeling emotion

• Papez circuit: thalamus receives stimulus → 1) hypothalamus (body response) 2) cingulate cortex (emotion)

body and brain can respond emotionally without

conscious awareness

Missatribution of arousal

emotion = physiological arousal + interpretation of the situation

Channelrhodopsin

used for optogenetics

light of certain frequency opens Na+ or Cl- channel → depolarization or hyperpolarization

Basic emotion theory

small set of emotions are built in by evolution

• universal facial expression

• own brain circuit

• rebutted by cultural differences ex) himba

Dimensional theory

points along continuous dimensions

• valence: unpleasant → pleasant

• arousal: mild → intense

Psychological constructionist theory

emotions are results of interactions between different general purpose brain networks

Brain network in psychological constructionist theory

network of regions that are active together across different brain imaging studies

psychological constructionist theory suggests that

each instance of emotion is contextually dependent

no network is specific to one emotion

Limbic lobe

cingulate cortex + hippocampus

• structures that border brainstem

papez circuit

neocortex <→ cingulate cortex (emotional experience) → hippocampus (memory) -(fornix)→ hypothalamus (emotional expression) → anterior nuclei of thalamus (sensory input)

cingulate cortex

processing of emotion

hippocampus

memory

fornix

connects hippocampus and hypothalamus

hypothalamus

emotional expression in body

thalamus

receive and integrate sensory input from body

emotional coloring

assigning of emotion to experiences, sensations, actions

Phineas Gage had a rod go through his

anterior cingulate cortex

• memory and intelligence was spared but major personality changes

amygdala

fear and learning

• assigns emotional significance to stimuli

basolateral nuclei

multimodal sensory input

• 80-90 percent of area

• integrate US and CS

• body → thalamus → basolateral nuclei

central nucleus

send output

corticomedial nuclei

olfactory sensory input from olfactory bulb

stria terminalis

connects amygdala to hypothalamus for quick expression of response to fear

emotional memory

amygdala strengthens hippocampal memory

fear requires visual stimulus information for less than

50ms

Unconditioned stimulus

innate fear

Conditioned stimulus

no innate response is associated with it

• can be associated with US to produce response → integration in basolateral nuclei

Amygdala outputs to hypothalamus

body response

Amygdala outputs to cortex

feeling emotions

Amygdala outputs to PAG

behavioral response

Kluver-Bucy syndrome

temporal lobectomy (remove amygdala)

• no fear

• indiscriminate eating

• inappropriate sexual behaviors

• visual agnosia

Patient SM

• Urbach-Weithe → calcification of both amygdalas

• no natural sense of where to look for to detect fear

• high response to excess CO2 inhalation

Patient SM suggests that

threat from inside body has different fear signaling than through sensory system outputs

• amygdala needed for fear of threats in environment but not for every feeling of fear

Intracranial EEG

can record / stimulate activity in deep brain structures

Amygdala stimulation in humans led to

more sweat and lower heart rate but no differences in feeling

• amygdala: drives body’s alarm but feeling is more involved with the brain

hypothalamus

involved in aggression

affective aggression

cerebral cortex → amygdala → medial hypothalamus -(dorsal longitudinal fasciculus) → PAG

predatory aggression

cortex → amygdala → lateral hypothalamus -(medial forebrain bundle) → ventral tegmental area (VTA)

cortex in aggression circuit

regulate activation of amygdala

amygdala in aggression circuit

add emotional significance, drives hypothalamus

hypothalamus in aggression circuit

1) stimulate brainstem (PAG, VTA)

2) produce hormones

— is required for sham rage

posterior hypothalamus

Aggression is a fixed action pattern

innate releasing mechanism

Insula

• inside lateral sulcus

• internal signals → emotions like disgust, empathy

  • ex) fast heart rate in mice → anxiety: need insula

Prefrontal cortex

the anterior part of the frontal lobe

• interconnected with amygdala, creates context specific fear

• reappraisal: reinterpreting the situation (lateral and medial)

• contextual modulation of pain

Dorsolateral (PFC)

executive function

• top-down control of emotions

Anterior cingulate

affect regulation

Orbitofrontal

context-specific learning, decision making, value encoding

• connects fear (amygdala) and memory (hippocampus)

Transorbital lobotomy

destroy prefrontal cortex → “calm” mentally ill indivuals

• logical abilities intact but planning, affect everything messed up