Lec 41 Limbic Behavior, Emotions, and Learning Flashcards
What are the major functions of the limbic system?
amygala = emotions + drive
hippocampal formation = memory
hypothalamus = homeostasis
olfaction
the 4 Fs –> fear, food, fight, fornication
What is the function of amygdala?
- assigns emotional valence to sensory input
- adds emotional content to declarative memories
- major output path to anterior hypothalamus [autonomic + endocrine]
- fear conditioning
- many connections
What are the 3 major areas of the prefrontal cortex?
- orbitofrontal cortex
- anterior cingulate cortex
- dorsolateral prefrontal cortex
What is the function of the nucleus accumbens?
- role in reward, pleasure, laughter, addiction, aggression, fear, placebo
What is the function of the hippocampus?
- memory formation
- inhibitory control of HPA [hypothalamic-pituitary-adrenal] axis
What is the function of the dorsolateral prefrontal cortex?
- cognitive control, solving complex tasks, working memory, decision making and planning
What is the function of the orbitofrontal cortex?
- corrects and inhibits maladaptive emotional responses
- mediates socially appropriate behavior
What is the function of the anterior cingulate cortex?
- mediates reward, anticipation, empathy, emotional response, motivation
What is the process of emotion perception?
stimulus present
- -> appraised via amygdala + insula
- affective state via amygdala, insula, anterior cingulate, orbitofrontal cortex, nuc accum
- regulation by anterior cingulate, hippocampus and prefrontal cortex
What is the neurochemistry of schizophrenia?
- hyperactivity of DA neruons in mesolimbic path mediates pos symptoms of psychosis
- hypoactivity of DA neurons in mesocortical path mediates negative + cognitive symptoms
What do you see in fMRI of pt with schizophrenia?
- decrease activity dorsolateral prefrontal cortex and dorsal anterior cingulate [ACC] during executive function/ memory
- decreased hippocampal activity during memory
- inability to engage amygdala, ACC, hippocampus in processing stimuli with high emotional valence
- dysfunctional interconnectivity between frontal and temporal regions
What is the learning theory?
- strengthen existing responses or formation of new responses to existing stimuli that occurs because of practice or repetition
What are the two types of non-associative learning?
habituation and sensitization
What is habituation?
- decreased responding after repeated stimuli
ex. filter out continuous stimuli in our surrounding environment
What is sensitization?
increased responding after repeated stimulation
What are the two types of associative learning?
classical + operant conditioning
What is long-term potentiation?
- example of sensitization
- mech underlying memory + learning
What is kindling?
- type of sensitization
- repeated stimulation hippocampal or amygdala neurons –> leads to seizures
after sensitized, little stimulation needed to produce seizures = model for epilepsy
What is central sensitization
- type of sensitization
- prolonged activity of dorsal horn neurons caused by repeated noxious stimulation causes increased neuronal responsiveness
–> cause hyperalgesia, allodyna = mech of chronic pain
What is drug sensitization?
- type of sensitization
- causes increased effect of drug with repeated doses
- -> craving, drug adverse effects
- -> neuroplastic changes in mesolimbic DA path
What is associative learning?
behavioral change caused by animal’s learning that particular temporal association occurs between two stimuli
ie associates presented stimulus with another stimulus or event such as reward or punishment
What is classical conditioning?
temporal association of neutral stimulus with a behaviorally vant unconditioned stimulus –> causes the neutral stimulus to bring about response similar to that normally associated with the unconditioned stimulus
What are the 4 key elements to classical conditioning?
unconditioned stimulus [US]: stimulus that without training produces a reflexive unlearned response [ex odor of food]
unconditioned response [UR]: response that occurs spontaneously to unconditioned stimulus [ex salivation]
conditioned stimulus [CS]: neutral stimulus that elicits conditioned response following learning [ex sound of a bell]
conditioned response [CR]: behavior learned by an association made between a conditioned stimulus and an unconditioned stimulus; = the response elicited by the conditioned stimulus [ex salivation in response to the sound of bell]
What are the 4 characteristics of classical conditioning?
acquisition = period when conditioned response [CR] is acquired
extinction = reduced CR when CS is repeatedly presented in absence of US with which it had previously paired CR = salivation at bell; CS = bell; US = smell of food
spontaneous recovery = increase in strength of extinguished CR after the passage of a period of time
stimulus generalization = elicitation of CR in response to new stimulus that resembles the original conditioned stimulus
What is learned helplessness?
- a type of classical conditioning
- association between aversive stimulus and inability to escape
- –> hopelessness, apathetic response during subsequent exposure to same or new aversive stimulus
What is imprinting?
- a type of classical conditioning
- process by which learning occurs at particular age or life stage
- rapid and independent of consequences of behavior
What is fear conditioning?
- type of classical conditioning
- aversive stimulus associated with particular neutral context or stimulus
- -> results in expression of fear response causing expression of fear response to the originally neutral stimulus
What happens in fear conditioning?
- components of implicit and explicit memory
- amygdala may play important role –> neurons in amygdala undergo plastic changes [LTP-like]
- hippocampus plays role in contextual fear conditioning
What is the fear network?
- sensory info comes into amygdala by 2 major paths
- —- short loop = direct sensory input from sensory thalamus = rapid response to potentially threatening stimuli
- —- long loop = from thalamus to cortex where processed/evaluated to amygdala to temper amygdala’s response
What is theory of anxiety disorder associated with fear netowrk
- anxiety disorder = deficit in higher cortical processing paths leading to failure to shut off amygdala
What is operant conditioning?
- trial and error learning
- learning due to consequences of previous behavior
- different from classical conditioning b/c deals with modification of voluntary behavior
What is positive vs negative reinforcement?
positive = introduce stimulus results in increase in rate of behavior negative = removal of aversive stimulus results in increase in rate of behavior
What is punishment?
introduction of aversive stimulus aimed at reducing rate of unwanted behavior
what is extinction?
gradual disappearance of learned behavior when reinforcement/reward is withheld
Are behavior effects of punishment or reinforcement more likely to be long term?
punishment = more temporary
reinforcement = longer term
What are the different types of fixed schedules of reinforcement?
continuous: reward given each time desired behavior occurs
fixed ratio: reward after designated # of responses
fixed interval: reward given after designated amount of time
What are different types of variable schedules of reinforcement?
variable ratio: reward given after random + unpredictable # of responses
variable interval: reward given after random and unpredictable amount of time
What is modeling?
- 3rd type of learning
- type of observational learning
- individual observes others and imitates their behaviors
- more efficient + faster than operant learning
What is neurobiology of operant conditioning?
- nucleus basalis ACh neurons activate after conditioned stimulus or primary reward
- dopamine plays role in positive reinforcement and aversive learning
What structures make up the reward pathway?
- cortex receives and processes sensory stimulus indicating reward
- sends signal to ventral tegmental area [VTA] of midbrain
- VTA —> dopamine to nucleus accumbens, amygdala, and prefrontal cortex
- amygdala acts on nucleus accumbens further
- nuc accumbens activates motor function to go after stimulus via ventral pallidum and structures of extrapyramidal motor system
- cortex allows integration of info, development learning and motivation
What is the effect of drugs on reward paths?
- activate brain regions normally control responses to natural rewards + important for survival
- drugs of abuse activate mesolimbic dopamine system and increase dopamine levels in nucleus accumbens
What type of reinforcement in drug use?
- early/occassional use = positive reinforcement to motivate behavior
- later/chronic/frequent use = negative reinforcement
What is kluvery-bucy syndrome?
- hypoactivity of limbic system [remove amygdala in monkey]
characterized by: hyperorality, hypersexuality, no fear, tameness
What is urbach-wiethe disease?
- rare autosomal recessive disease
- have bilateral calcifications of anterior temporal lobes [esp. amygdala]
- normal intelligence/ language/ memory for neutral stimuli
- impaired long term memory for emotionally intense stimuli
- cannot properly rate intensity of emotion or recognize a fearful expression
What are the neural pathways for empathy?
- insula = experience painful emotions, observe them in others
- anterior cingulate cortex = tell when something is wrong
- amgydala/orbitofrontal cortex/ventromedial prefrontal cortex = experience empathy and maintain socially acceptable behavior
What are symptoms of sociopathy?
- lack of respect for social norms
- reckless, irritable, impulsive, aggressive
- lack of remorse/guilt
- lack of empathy, compassion, fear
- repeated lying and conning other for personal benefit and pleasure
- failure to plan ahead
- symptoms generally onset before age 15
What limbic dysfunction causes sociopathy?
- amygdala and orbitofrontal cortex hypoactivity
- ventromedial prefrontal cortex dysfunction
- reduced activity insular and angterior cingulate cortex regions related to cooperative tasks, emotional recognition
What is limbic encephalitis?
- group of autoimmune disorders affecting limbic system
- usually caused by paraneoplastic autoimmune syndrome
What is cardinal sign of limbic encephalitis? other symptoms?
- subacute onset short term memory loss
other:
- behavioral, psych, confusion, seizures
What is the neuropathology of limbic encephalitis? etiology?
- mononuclear inflammatory cell infiltrates, loss of neurons, and proliferation of astrocytes/microglia in hippocampus and amygdala
etiology: autoimmune –> anitbodies against intracellular antigens or neuronal surface antigens
What are the 3 major groups of limbic encephalitis?
- LE associated witih classic onconeural antibodies = majority associated with neoplasm
- LE associated with antibodies agaisnt neuronal surface/synaptic antigens
- LE associated with not known antibody = many associated with neoplasm
What are clinical findings of limbic encephtalitis?
CSF –> may find anti-neuronal antibodies, high lymphocytes and protein
EEG –> seizure/epileptiform activity in temporal region or slow wave
MRI –> hyperintense signals, mild swelling medial temporal lobes
PET –> hypermetabolism in medial temporal lobes
What kind of limbic encephalitis causes ovarian teratoma? other symptoms?
- antibody to NMDA-R
other symptoms: psychiatric, dystonia, depressed consciousness, hypoventilation, seizures
What is herpes simplex encephalitis?
- usually caused by HSV1 infection of medial temporal lobe and inferior fronal lobe
- due to direct transmission from periphery via CN 1, 5
- causes inflammation, necrosis, hemorrhage
acute = confusion, seizures, impaired memory/consciousness
progressive in 7-14 days and often fatal if untreated
What is temporal lobe epilepsy?
- reccurent epileptic seizures from 1 or both temporal lobes [medial or lateral]
- seizure symptoms: hallucinations, illusions, amnesia, mood changes, fear, anger
- characteristic personality syndrome: hyperreligiosity, circumstantiality, hypermortality, altered sexuality
What are signs of frontotemporal dementia?
- personality change, inappropriate behavior, apathy, mood symptoms, language impairment
What happens in alzheimers disease?
- impaired memory and lanuga; paranoia and delusions
- due to hippocampal dysfunction
