Limbic system Flashcards
Describe a way to find the amygdala.
Simple: Find fornix, go to hippo, at distal end of temporal lobe you’ll run into amygdala.
Complicated: Beneath the uncus of the limbic lobe, at the anterior end of the hippocampus and the inferior horn of the lateral ventricle.
What are the 3 major groups of nuclei in the amygdala?
Which is the biggest?
- Medial
- Central
- Basolateral (biggest)
What’s the role of the medial amygdalar nucleus?
Interconnected w/the olfactory system
small
What is the central amygdalar nucleus important for? Connections to what brain centers make this so?
Emotional responses/*visceral sensory input
- Hypothalamus + all brainstem (e.g. PAG)
What’s the main role of the basolateral amygdalar nuclei?
Key link of the experience of emotions and their expression.
What cortical area is the amygdalar basolateral nuclei closely associated w/?
Parahippocampal cortex
What general type of input do the amygdalar basolateral nuclei receive? (and from what 2 brain areas?)
What other part of the amygdala do they communicate w/?
- Sensory (from cortex and thalamus)
- Central nucleus
What type of cell would you find in the basolateral amygdalar nuclei that you’d also find in some layers of the cerebral cortex?
Pyramidal cells
Where do the basolateral amygdalar nuclei get their input from regarding sights, sounds, touches, smells, and tastes?
Thalamus + unimodal visual, auditory, somatosensory, and gustatory association areas
What 3 cortical areas do the basolateral amygdalar nuclei get their input from regarding levels of physical and emotional comfort and discomfort?
Orbital, anterior cingulate, and the insular cortices
Fibers leave the amygdala through the ______________ and the _____________ to reach many of the same areas that send afferents to it.
- Stria terminalis
- Ventral amygdalofugal pathway
Efferents from the amygdala to the thalamus primarily terminate in the:
a. Anterior nucleus
b. Dorsomedial nucleus
c. Lateral geniculate nucleus
d. Pulvinar nucleus
e. Ventral lateral nucleus
b. Dorsomedial nucleus
T/F - amygdala efferents can feed directly into the cortex. If false, what do they relay through?
True
Explain, in detail, the different functions of the amygdala.
- While hippo remembers event, amygdala remembers whether it was “good” or “bad”
- Triggers appropriate responses to help decide what to do (“gut feelings”) for future similar events
- Conditioned responses
- Fear response
Bilateral lesions to the tips of the temporal lobe would cause what syndrome?
Kluver-Bucy syndrome
What are the sx that characterize Kluver-Bucy syndrome?
- Docility
- Hyperorality
- Hyperphagia
- Visual agnosia
- Hypersexuality
What structures make up the hippocampus?
- Dentate gyrus
- Hippocampus proper
- Subiculum
What’s the subiculum of the hippocampus?
A transition zone between the hippocampus proper and temporal lobe neocortex.
Describe the physical structure of the hippocampus.
How many layers it is?
2 interlocked letter C’s
- 3 layers (like cerebellum)
The anterior part of the parahippocampal gyrus is the major interface between the hippocampus and vast areas of association cortex, allowing the hippocampus to serve as a key link underlying ________________.
Declarative memory (AKA explicit memory: long-term facts and verbal knowledge)
What’s another name for the parahippocampal gyrus?
Entorhinal cortex
Damage to the hippocampus and/or surrounding related areas could lead to what?
Anterograde amnesia (can’t form new memories)
Since retrograde amnesia following damage to the hippocampus only lasts a few hours/days, what does that mean about the storage of long-term memories?
They are stored outside the hippo
What are the major inputs to the entorhinal cortex on their way to the hippo?
What about those that bypass the entorhinal cortex and go straight to hippo?
- Unimodal areas, multimodal areas, limbic areas
- Septal nuclei and amygdala
How do modulatory cholinergic inputs from septal nuclei reach the hippocampus?
Travel back through the fornix, a major output route from the hippo
What’s the reason memories receive input from the amygdala?
*Amygdala affects probability of whether or not something will be remembered as a declarative memory based on our emotional reaction to it.
What are the major cortical “areas” that receive output from the hippocampus, by way of the entorhinal cortex?
Unimodal areas, multimodal areas, limbic areas
Besides the entorhinal cortex, what’s another major efferent projection for the hippocampus?
*Projections to the mammillary body through the fornix
The fornix curves around with the lateral ventricle; it separates from the hippocampus near the __________________________, travels forward along the inferior edge of the septum pellucidum, turns downward in front of the interventricular foramen, and enters the __________________.
- Splenium of the corpus callosum
- Hypothalamus
Recall: Which part of the thalamus do the mammillary bodies project to?
How do they get there?
- Anterior nucleus
- Mammillothalamic tract (part of Papez circuit)
What common, commonly age-related disease affects the hippocampus?
What are other ways to dmg the hippo?
- AD
- Oxygen starvation (hypoxia), encephalitis, or medial temporal lobe epilepsy
Bilateral temporal lobe lesions cause anterograde amnesia, as well as retrograde amnesia to semantic memories immediately prior to the event. Would this apply to declarative memories, nondeclarative memories (skills/procedures), or both?
Declarative only
- Patients could learn to assemble a puzzle with greater skill on each attempt, but not remember having ever seen the puzzle before.
- The function of laying down or consolidating memories has been attributed, therefore, to the hippocampus (but stored elsewhere)
Besides acting like a memory “index” (keeping track but not storing them), what other areas does the hippo appear to play a role? (just read it)
Aging, stress, epilepsy, schizophrenia and transient global amnesia.
What type of memory are the mammillary bodies critical for?
*Spatial memory (position of head in space)
What’s Wernicke-Korsakoff’s syndrome?
What are the causes of it?
What are the sx?
- Disabling degenerative brain disorder
- Lack of thiamine (vitamin B1) due to alcohol abuse, dietary deficiencies, prolonged vomiting, eating disorders, or chemo
- Mental confusion, confabulation, attention deficit, memory impairment (both anterograde and retrograde), vision impairment, stupor, coma, hypothermia, hypotension, and ataxia.
Regarding Wernicke-Korsakoff’s syndrome, what’s the name of the acute phase of the disorder?
What’s the name of the chronic phase of the disorder?
- Wernicke’s encephalopathy
- Korsakoff’s amnesiac syndrome (memory disorder, confabulation)
What are the functions of the septal nuclei?
- Regulates gonadal hormone secretion and various reproductive/sexual behaviors
- Facilitates memory formation (projects to hippo)
What are the 3 afferents and 5 efferents of the septal nuclei?
Afferents: Hippocampus, Amygdala & Preoptic area of hypothalamus
Efferents: Hippocampus, Amygdala, Preoptic area of hypothalamus, Mammillary body & Median eminence
Lesioning the septal nuclei would result in what?
- General behavioral overreaction, particularly evident as “septal rage.”
What type of seizure disorder is closely associated w/the limbic system?
Temporal lobe epilepsy
