Limbic System Flashcards
What path does the fornix take?
From the hippocampus to the mamillary body, sepal nuclei.
What tract travels from the body of the mamillary body to the anterior thalamic nucleus?
Mamillo-thalamic tract
What travels from the amygdala to the septal nuclei?
Stria terminalis
What travels from the midbrain to the forebrain via the hypothalamus?
Medial forebrain bundle
What travels from the hypothalamus to the brainstem and spinal cord, giving off branches to the pons, medulla, and spinal cord?
Dorsal longitudinal fasciculus
Where does norepinephrine in the limbic system come from?
Locus ceruleus (LC) in the pons
Where does serotonin (5HT) in the limbic system come from?
Raphe nuclei (Ra) in the midbrain, pons, and medulla
What region in the mesolimbic system is associated with dopamine?
Ventral tegmental area (VTA); just medial to the substantia nigra. Axons from nucleus accumbens, medial prefrontal cortex, amygdala, & septal nuclei zip through here.
What do cocaine and amphetamines do to dopamine levels?
-Cocaine blocks dopamine reuptake, thus increasing the concentration in the synaptic cleft. —Amphetamine blocks dopamine reuptake as well as promote secretion of dopamine.
What neurotransmitter is associated with nucleus basalis and septal nucleus?
Acetylcholine. In alzheimers, Nucleus Basalis is lost, memory deficits. Acetylcholine is important in memory.
What happens to learned and conditioned behavior if the amygdala is lesioned?
No conditioning can happen and there is immediate extinction of learned behavior.
What symptoms are seen in a prefrontal lobe syndrome?
- Impairment in goal directed behavior
- Lack of emotion in decision-making (lack of risk aversion)
- Poor social judgement (antisocial behavior)
- Poor emotional control (increased impulsivity)
What does the dorsolateral prefrontal cortex (DLPFC) play a major role in?
Working memory
Why does the orbital frontal cortex play a major role in prefrontal lobe syndrome?
It is connected to the amygdala, inhibiting it. Without it, more prone to fits of emotion. Prefrontal cortex is inhibitory to the amygdala, which is excitatory on the hypothalamus.
What is the hippocampus important in?
Memory consolidation, specifically explicit or declarative memory.
What is anterograde amnesia?
No new memories
What is temporally graded retrograde amnesia?
You can’t remember past events well in a graded fashion; recent past events are harder to recall then events long ago.
Differentiate between semantic and episodic memories.
Semantic- facts
Episodic- experiences
*Hippocampus is needed for this
What types of memory is the hippocampus not needed for?
Procedural or nondeclarative/implicit AKA motor memory
What disease is indicative of:
- impaired recognition of emotions (fear and anger)
- Memory loss especially w/emotional content
Urbach-Wiethe disease (bilateral damage due to mineral deposit in amygdala)
- Re-experiencing phenomena i.e. flashbacks
- Avoidance of situations that parallel initial trauma
- Hyperarousal i.e. increased anxiety..hallmark
Post Traumatic Stress Disorder (PTSD)
-Hyperactivity of amygdala, little inhibition by medial prefrontal cortex
Fragmentation of mood, thought, and action.
Positive symptoms: Delusions, hallucinations
Negative symptoms: Social withdrawal
Schizophrenia (1% of U.S. population)
What is the dopamine hypothesis of schizophrenia?
There is an increase in DA receptor activity.
-Amphetamine psychosis from taking amphetamines too long, lots of DA
Treatments of schizophrenia?
Haloperidol: D2 receptor blocker. Causes Parkinson like disorder
Clozapine (atypical anti-psychotic):
- D2 receptor blocker, but leaves receptor fast
- 5HT receptor blocker
- Blocks glutamate reuptake, thus increased glutamate
What is the glutamate hypothesis of schizophrenia?
Phencyclidine (PCP) aka angel dust blocks NMDA receptor, thus decreasing glutamate and causing psychotic symptoms. Treat by increasing glutamate.
What are the symptoms of depression?
-Anhedonia: loss of interest in pleasurable/rewarding behaviors
-Sleep wake problems
-Social withdrawal
20% of women, 13% of men
What are the treatments for depression?
Treat decreased NE and or 5HT receptor activity:
- Monoamine oxidase inhibition
- Tricyclics (Imipramine): blocks reuptake of NE and 5HT
- Serotonin specific reuptake inhibitors (SSRIs) e.g. fluoxetine
- Disorder of immediate memory
- Disorientation
- Confabulation
*Damage to mamillary bodies or mamillo-thalamic tract
Korsakoff’s syndrome
-Chronic alcoholism associated with this because it ultimately leads to a vitamin b1 deficiency
- Oral tendencies
- Changes in emotions (even keel, nothing bothers them due to loss of amygdala)
- Hypersexuality (increased number and variety of sexual activities due to loss of pathways to hypothalamus)
- Visual agnosia (AKA psychic blindness. Inability to discriminate visual stimuli due to lost input from visual cortex.)
Kluver-Bucy Syndrome: bilateral medial temporal lobe damage.
- Memory loss
- Mood changes: anxiety and depression
- Motor dysfunction
- Complete loss of cognitive function
Alzheimers Disease (over 50% of ppl over 85)
- loss of chlinergic input to hippocampus (antiacetylcholinesterases? don’t work well)
- Loss of neurons in multiple brain areas
- Presence of NFT and beta amyloid plaques
What disease is caused by repeated head trauma and mimics prefrontal cortex damage?
Chronic traumatic encephalopathy (CTE)
