Lectures 41, 42: Limbic System Flashcards
Major functions of limbic system and associated structures (4)
Emotions and drives (amygdala), memory (hippocampus), homeostasis (hypothalamus), olfaction
Amygdala
Emotional valence to sensory inputs and declarative memories, major output pathway to the anterior hypothalamus (autonomic and endocrine responses), fear conditioning
Nucleus accumbens
Reward, pleasure, laughter, addiction, aggression, fear, placebo effect
Hippocampus
Memory, inhibit HPA axis
Areas of PFC and major functions (3)
Dorsolateral PFC (executive function, cognitive control), Orbitofrontal cortex (corrects/inhibits maladaptive responses and socially appropriate behavior), Anterior Cingulate Cortex (reward, anticipation, motivation)
Modulatory input NTs
5-HT, ACh, DA, NE
Major brain area modulating limbic system
Prefrontal cortex
Process of emotional perception
Stimulus –> appraisal (amygdala, insula) –> affective state (amygdala, insula, ACC, OFC, NA) –> regulation (PFC, ACC, hippocampus)
Schizophrenia involves which DA projections? What is hypo/hyper active
Mesolimbic (hyperactive), Mesocortial (hypoactive)
Learning (theory)
Strengthening of existing responses/behaviors or formation of new responses to existing stimuli that occurs because of practice or repetition
Habituation
Repeated stimulus –> decreased responses
Sensitization and some examples
Repeated stimulus –> increased response (LTP, kindling, chronic pain, addiction)
Classical conditioning
Neutral stimulus w/ unconditioned stimulus –> neutral stimulus causes response of unconditioned stimulus
Classical conditioning symbols
US –> UR; US + NS –> CR; CS –> CR
Spontaneous recovery
Increase in the strength of an extinguished behavior after
the passage of a period of time
Stimulus generalization
Conditioned response as a result of a new stimulus that resembles conditioned stimulus
Learned helplessness
Association (by classical conditioning) between aversive stimulus and inability to escape leads to hopeless, apathetic response during subsequent exposure to same or new aversive stimulus
Imprinting
Learning occurring at a particular
age or a particular life stage that is rapid and independent of the consequences of behavior
Fear conditioning requires what structure?
Amygdala
Fear Network pathway, long loop
Afferents –> sensory thalamus –> cortex (appraisal) –> amygadala –> brainstem, hypothalamus for flight/fight response
Fear Network pathway, short loop
Afferents –> sensory thalamus –> straight to amygdala!
Operant Conditioning is basically…based on what feedback?
Trial and error learning based on reinforcement (positive or negative, punishment)
What is negative reinforcement?
Behavior strengthened by avoiding an aversive consequence
Which is better, reinforcement vs punishment?
Reinforcement
Two schedules of reinforcement and subtypes
Fixed (continuous, fixed ration/interval) or Variable (ratio/interval)
Best schedule of reinforcement for extinction. Down side?
Variable; slow
Neurobiology of operant conditioning and NTs
Nucleus basalis (ACh) activated after conditioned stimulus; DA for positive reinforcement
All drugs of abuse activate…increase DA where?
Mesolimbic DA system and increase DA in NA
Describe Kluver-Bucy Syndrome
No amygdala = hyperorality, hypersexuality, no fear/aggression
Describe Urbach-Wiethe disease
Rare genetic disorder, calcifications on amygdala –> cannot rate intensity of emotion/recognize fear expression
Structures involved in empathy and associated functions (3)
Insula (experience painful emotions, imitate them, observe similar emotions); ACC (error in behaviors); Amygdala and frontal regions (empathy and maintaining socially acceptable behavior)
In socipathy, where is dysfunction?
Amygdala/OFC/VMPFC/Insula/ACC
Describe limbic encephalitis
Group of autoimmune disorders predominantly affecting of limbic system related to a tumor but usually presents BEFORE malignancy diagnosis
How does limbic encephalitis present?
Subacute short term memory loss w/ other psych symptoms; other causes are ruled out
Three major groups of limbic encephalitis
- Classical onconeural Abs against intracellular neuronal antigens; 2. Abs against neuonral surface/synapses; 3. No known Ab
Examples of onconeuronal (ovary)
F
Describe herpes simplex encephalitis cause, presentation, prognosis
HSV-1; confusion, personality change, seizures, impaired consciousness, fever, impaired memory –> quickly fatal if untreated
Temporal lobe epilepsy
Seizures associated with fear, emotional responses
Two types of dementia associated with limbic system
Frontotemporal dementia and Alzheimer’s Dementia
Hippocampus critical to what memory function?
Forming (not storing) new memories
Describe limbic control of the HPA axis
Excitatory control from amygalda, inhibitory control from hippocampus (via GABAergic cells) –> CRF
Cortisol excites/inhibits hippocampus. This is what kinda of feedback? So, excessive levels of cortisol can cause what?
Excites; negative feedback; hyperactivity in hippocampus, leading to damage and pathological feed-forward (more cortisol)
The cellular circuity of hippocampus is all (NT) modulated by what? (2)
Glutamatergic; GABAergic interneurons and ACh from septum
Amygdala is critical to what memory function?
Associative memory
Bilateral lesions of amygdala comprise what syndrome. Describe.
Kluver-Bucy Syndrome; placidity, loss of fear, hypersexuality, and hyperphagia
T/F: Amygdala and hippocampus are rarely foci of epilepsy
False: major epileptic focus
Amygdala circuitry sends projections to which two major regions?
Forebrain AND hypothalamus (CRF release) & brainstem nuclei
Two primary functions of PFC
- Working memory; 2. Executive control
Nucleus accumbens and septal nuclei are both…
Reward regions
Septal nuclei provide…
Strong cholinergic innervation of hippocampus
Bed nucleus of stria terminalis gets output from? What psych disorder is this important for?
Output of amygdala, particularly implicated in anxiety
Lateral habenula
Important interconnections with most other limbic structures
Long-term memory storage is called what and requires what? Retrieving memory is called what? What does this do?
Consolidation, requires gene transcription; reconsolidation strengthens memory but also makes in unstable
Three molecular bases for memory
Synapse-specific (LTP, LTD), whole cell plasticity (altered excitability) and changes in dendritic spines/nerve terminals
Define declarative memory and what mediates it (2 brain regions)
Semantic/episodic with exquisite temporal features; hippocampus and amygdala
Fear conditioning is a type of what kind of memory?
Declarative
What type of cell has shown us that the hippocampus is important for spatial memory?
“Place Cells”
Hippocampus required for _______ fear conditioning, amygdala required for _______ fear conditioning
Contextual (environment); cue (unconditioned stimulus)
Define procedural memory and what mediates it (brain region)
Habit/motor memory; striatum
Define working memory and what mediates it (brain region)
The ability to keep things in mind (prefrontal cortex)
NA/VTA are crucial for signaling what aspect of memory?
Rewarding/punishing memory (good or bad)
The septum uses what NT to contribute to memory?
ACh
Where are memories likely stored?
PFC
Emotional memory storage mediated by what system?
Monoamine systems
Define social cognition
Ability to perceive others feelings from subtle cues
What hormones are implicated in social cognition and what are each related to?
Oxytocin (affiliation) and vasopression (anxiety)
