lecture 20 - Emotions, Reward, Addiction

primary difference between emotions and feelings

emotions - reactions to events or state due to release of chemicals in brain

feelings - how you feel inside your bode, physical sensations, messengers from the body

conscious vs unconscious

emotions are automatic and unconscious (fight, flight, freeze and fawn)

feelings are conscious influenced byt cultire, religion, society

emotion speed + length

instant, fleeting, short term

feeling length

may or may not be related to emotion

long-term, settled in body

purpose of emotion + feeling

emotion -help us understand what we like and what we don't like

feeling - about how we interpret emotions

emotion + feeling visibility

emotions seen through expressions

feelings can be hidden

universal emotions

fear, anger, joy, sadness, disgust, surprise

duchenne smile

a true emotional smile which cannot be faked, can't be voluntarily produced

what did duchenne say

voluntary expressions cannot reflect real true emotion

what is volitional movement controlled by

descending pyramidal and extrapyramidal projections from motor cortex and brainstel

what kind of smile does volitional movement control

pyramidal

what is a voluntary facial paresis

defect of volitional movment

what is emotional expression controlled by

descending extrapyramidal projections from medial forebrain and hypothalamus

what kind of smile does emotional expression cause

duchenne smile

what is emotional facial paresis

defect of the neural systems that control emotional expression

where are the motor neurons activated by pyramidal and extrapyramidal projections located

facial nucleus

what cranial nerve is involved

cranial nerve # 7

what does the limbic lobe contain

- cingulate gyrus

- corpus callosum

- fornix

- cut edge of midrain

- temporal lobe

- parahippocampal gyrum

what does the limbic lobe form

a rim/limbus around the corpus callosum and diencephalon

what is the papez circuit

proposed circuit for emotional processing

main pathways to the hippocampus

what does the papez circuit consist og

cinculate cortex, fornix, thalamus, mammillary bodies, hippocampus

what is the papez circuit missing

amygdala, frontal cortex (emotional centers)

what is the function of the classic hypothalamus

- neuroendocrine function through connections with the pituitary gland

- sleep/wake circadian rhythms

- feeding and breeding (parasympathetic system)

what is the emotional hypothalamus

autonomic expression of emotions through activation of sympathetic system

expression of innate and conditioned defensive behaviors

what changes does the emotional hypothalamus code for

heart rate, temperature, sweating depending on the situation

what does the hypothalamus coordinate

visceral and somatic motor components of emotional behavior

what were philips bard's experiments called

sham rage

what did sham rage entail

- removed both cerebral hemispheres of a cat as well as underlying white matter and basal ganglia

- after anesthesia, animals acted enraged

- autonomic: increased BP and heart rate, dilation of pupils, piloerection

- somatic: arching back, extending claus, snarling/hissing

no obvious target causing rage

hypothalamus & coordinated rate response

necessary & sufficient

where is the amygdala found

temporal lobe, adjacent to hippocampus

what is the amygdala responsible for

relating sensory stimuli with emotional experience

site of associative learning

where does the amygdala connect

cortex, hippocampus, hypothalamus, thalamus, basal ganglia

connection between amygdala and higher order circuits

required for higher order processing of emotion and behavior

where is the stream of thinking from amygdala

through cortex

where is the stream of feeling from amygdala

through hypothalamus, papez circuit

what disease did patient SM have and what did it do

Urbach-Wiethe disease, destroyed amygdala bilaterally/bilateral lesions of amygdala

what symptoms did patient SM have as a result

- physically unable to feel fear

- cannot recognize fear in facial expressions

- does not have a concept of personal space

- does have a startle response not dependent on the amygdala

- can follow group fear responses due to voices and body responses in others

- has survived physical abuse and had a knife held to her throat

innate emotional response

autonomic

e.g. even lab rats display fear when exposed to fox odor

learned emotional response

conditioned; depend on experience

emotional learning

can be conscious but is often subconscious

what is emotional learning

construction of implicit memories linking a situation or event to an emotional body state

what is fear conditioning

when an innate reflex is modified by associating the normal trigger stimulus with an unrelated stimulus

rat - fear conditioning

neutral auditory tone (conditioned stimulus) is paired with a shock (unconditioned stimulus)

basically association and when they hear the tone, amygdala circuit gets actvated

what is the purpose of fear conditioning

enhances survival responses - freezing, changes in blood pressure, etc.

fear and memory

different brain regiosn

where is fear

SM doesn't have a fear response but has no deficit in a memory task

- amygdala required for fear but not for memory

wher eis memory

WC shoes appropriate fear responses byt major deficit in memory task

- hippocampus not required for fear learning but required for memory

what are the 3 major dopaminergic pathways

nigrostratial, mesolimbic, mesocortical

origin of nigrostriatal

substantia nigra

location of terminal boutons for nigrostraital

neostriatum (caudate nucleus and putamen)

behavioral effects of nigrostriatal system

control of movement

origin of mesolimbic system

ventral tegmental area

location of terminal boutons for mesolimbic

nucleus accumbens

behavioral effects of mesolimbic system

reinforcement, effects of addictive drug

mesocortical system origin

ventral tegmental area

mesocortical system location of terminal boutons

prefrontal cortex

behavioral effects of mesocortical system

short-term memories, planning, strategies for problem solving

what does meso/midbrain include

substantia nigra, ventral tegmental area

purpose of reward system

promotes survival

mesolimbic pathway purpsoe

primary reward synapse in the brain

reinforces behavioral movments - more DA signaling increases motivation to perform these behaviors again in the future

reward synapse

VTA to NAc

ventral tegmental area to nucleas accumbens

draw out mesolimbic system

herl

what are the five major brain regions involved in reinforcement and reward

VTA (ventral tegmental area), nucleus accumbens, basal ganglia, hippocampus, prefrontal cortex

purpose of VTA

source of dopamine cell bodies sending axon projections to nucleus accumbens

purpose of nucleus accumbens

receives dopamine inputs (axon terminals) from VTA

- all addictive drugs produce an increase of dopamine

purpose of basal ganglia

increases motor output to produce an overall increase in behavior

hippocampus

tells nucleus accumbens where we are and what is happening around us (our "context")

prefrontal cortex purpsoe

provides nucleus accumbens with several options for behavior

rats + VTA-NA Pathway

rats work to electrically stimulate and/or self-administer drugs to activate the VTA-NA pathway

blockade of DA receptor signaling in NA eliminates these behaviors

neural activity of DA neurons in VTA during reward learning

during learning, VTA increases neural response to an unexpected juice reward

after learning, VTA increases neural response to PREDICT juice reward

when reward is predicted but not delivered, VTA neural activity is suppressed

what do abuse-prone drugs do

enhance brain stimulation reward or lower brain reward thresholds

effects of nicotine on NAc

binds to Ach receptors on VTA neurons to cause depolarization

increase glutamate release onto VTA neurons

both increase DA release from VTA into NAc

effects of cocaine and amphetamine on NAc

block DA reuptake into VTA axon terminals to increase effect of DA in NAc

effects of opiates on NAc

bind to opiod receptors on axon terminals of GABAergic interneurons

opiates are inhibitory and decrease GABA release

disinhibits VTA neurons and increases dopamine release in NAc

what is addiction

corruption of dopaminergic neurons extending from VTA

what do addictive drugs do and what does it result in

artificially increase dopamine levels in situations that would normally have lower levels of dopamine which affects perception/processing of reward

how to reinforce addictive behavior

increasing dopamine at wrong time/circumstance

control vs addicted subjects

addicted subjects have lower D2 receptor expression and lower baseline dopamine release, which causes a blunted response to natural rewards such as food and sex

drug induced dopamine overcomes baseline deficiencies