Physiology of Emotion and the Limbic System

Question 1

Great Limbic Lobe

Answer 1

• described by Broca

- medial surface of brain under cortex, area containing gray matter (neurons); forms a kind of border around brainstem

Question 2

Papez Circuit

Answer 2

• argument that emotion is not from one brain center, but 4 interconnected structures: hypothal and mammilary bodies, anterior thalamic nucleus, cingulate gyrus, hippocampus
• (emotional expression governed by hypothalamus; cingulate to hippocampus, hippo to hypothal via fornix; hypothal to cortex via anterior thalamic nuclei)

Question 3

emotion

Answer 3

-the complex psychophysiological experience of
an individual’s state of mind, interacting with
environmental influences.
-links b/t physiological arousal, expressive behaviors, action tendencies, sensory stimuli and conscious experience (feelings)
-mediate the individual’s relation to a continually changing social environment

Question 4

mood

Answer 4

• affective states
• more unfocused/diffuse than an emotion.
• constructs depicting an individual’s emotional state

Question 5

cognition

Answer 5

refers to a faculty for the processing of information, applying knowledge, and changing preferences. It includes such processes as memory, attention, language, problem solving, and planning

Question 6

appetitive reflexes

Answer 6

reflexive ingestion and
enteric reflexes move some stimuli through
enteric system, reject others

Question 7

affect

Answer 7

refers to the experience of feeling or emotion

-the external and dynamic manifestations of a person’s internal emotional state

Question 8

personality

Answer 8

-refers to characteristic patterns of thoughts, feelings, and behaviors that a person exhibits fairly consistently thru life.

Question 9

Neurophysiology of emotion: 4 most important structures

Answer 9

• amygdala
• ventral tegmental area
• nucleus accumbens or ventral striatum
• ventromedial prefrontal cortex

Question 10

amygdala

Answer 10

• primary roles in the formation and storage of memories associated with emotional events
• studied via fear conditioning
• Sensory stimuli reach basolateral complexes of amygdalae (esp lateral nuclei); where they form associations with memories of the stimuli.
• mediated via LTP
• Memories of emotional experiences are imprinted in strengths of synaptic connections in lateral nuclei of amygdalae (=basolateral amygdala–BLA)
• BLA elicit fear behavior thru connections w/ central nucleus of amygdala (CEA), and related bed nuclei of stria terminalis (BNST) (BNST–>release of pituitary -adrenal stress hormone CRH in response to fear.

-Amygdala links aversive and appetitive stimuli with
physiologic responses, action patterns, perceptions, and
predictions

Question 11

Central nuclei and fear responses

Answer 11

freezing (immobility), tachycardia (rapid heartbeat), increased respiration, and stress-hormone release
-central nuclei mediates EXPRESSION of emotional responses

Question 12

What doesn’t happen without amygdala?

Answer 12

acquisition and expression of Pavlovian fear conditioning

Question 13

BLA

Answer 13

• basolateral amygdala
• sensory inputs from cerebral cortex and thalamus
• (glutamatergic) projections from BLA to CEA
• BLA to nucleus accumbens too
• Main output of amygdala= CEA–>GABA

Question 14

CRH release causes ___

Answer 14

adrenal gland to release epinephrine and cortisol.

Question 15

Positive and negative stimuli responses in amygdala

Answer 15

• neurons respond to one or the other, but they aren’t clustered anatomically
• Appetitive involvement (reward) project to nucleus accumbens in ventral striatum
• Involved in fear or aversive conditioning project to the CEA

-BLA receives sensory info from multiple areas, w/ appetitive OR aversive outcomes.
-BLA projects to many downstream regions: reward and fear.
(BLA to Nucleus accumbens for reward related behaviors, BLA to CeM–part of CEA– for conditioned fear)

Question 16

fear extinction

Answer 16

-when CS is presented without US, conditioned fear responses diminish
-But, return of fear after extinction occurs over time.
=inhibitory memory that temporarily suppresses the expression of fear associations.
(rat: medial Prefrontal cortex (mPFC) projects to BLA, CeA, and ICMs. Stimulation of mPFC inhibits CeA responses to afferent stimulation;mPFC may modulate ICM activity either directly or indirectly (i.e., via the BLA) and thereby gate amygdala throughput and suppress triggering of fear responses in extinction.)

Question 17

Ventromedial Prefrontal Cortex (orbitofrontal cortex)

Answer 17

VMPFC

• lesions lead to characteristic action on Iowa Gambling Task–continually draw from “bad decks”
• impaired anticipatory emotional stress responses, intact responses for reward/punishment.
• So: VMPFC is necessary for the prediction of consequences, but not necessary for registering the actual consequences.

-VMPFC lesion: inadequate inhibition of aggression, sexual behavior, anxiety, and appetitive functions. They also fail to correctly employ these behaviors in appropriate circumstances. Ex Phineas Gage

Question 18

Self stimulation

Answer 18

• aversive: PAG
• neutral: most, including neocortex
• positive: medial forebrain bundle (key = dopaminergic neruons in ventral tegmental area of midbrain, near SNPC)
• positive: nucleus accumbens (the subregion of the striatum that receives input from, and projects output back to, the VMPFC)= VMPFC-nucleus accumbens-corticostriatal loop.
• ->dopamine is reinforcing here

Question 19

reward prediction error hypothesis

Answer 19

-DA encodes difference between the experienced and predicted reward of an event. (dopamine updates the value of different actions and stimuli)

Question 20

Iowa gambling task/lesions and poor performance

Answer 20

• Lesions in VMPFC or amgydala had impaired performance, both lack anticipatory stress responses.
• BUT amygdala lesions also failed to show sin conductance responses–>impaired ability to register emotional impact of rewards and punishments from specific behaviors.

Question 21

Insula

Answer 21

The Insula constitutes primary olfactory, gustatory, and
visceral sensory cortex. Links between insula, VMPFC,
and amygdala relate these senses to emotion

Question 22

VMPFC and ventral striatum

Answer 22

VMPFC and ventral striatum are (respectively) critical for

generating and reinforcing predicitons about the risks and rewards associated with actions

Question 23

VTA

Answer 23

VTA (reward and punishment and salience) signals

contribute to synaptic plasticity and associative learning in the amygdala, ventral striatum, and VMPFC