Exam #3: Limbic System Flashcards
What are the general functions of the limbic structures?
- Memory
- Defense
- Reproduction
What are the major structures of the limbic system? What are the two major structures of the limbic system?
- Cingulate gyrus
- Subcallosal gyrus–located below the corpus callosum
- Parahippocampal gyrus
- Hippocampus
- Amygdala
- Septal area/ nuclei of the thalamus & hypothalamus
**Hippocampus (memory) & amygdala (emotions) are the main regions
What is the gyrus that lies above the corpus callosum?
Cingulate gyrus
Describe the shape of the amygdala.
Almond-shaped
Where are the septal nuclei?
Located on either side of the septum pellucidum in the lateral ventricle
What is the major input into the limbic system that we covered in class?
Olfaction via the olfactory tracts
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**Specifically, the lateral olfactory stria (division of the olfactory tracts) synapse with the
1) amygdala
2) primary olfactory cortex i.e. piriform lobe & uncus
What commissure carries olfactory information that crosses over?
Anterior commissure (specifically the medial olfactory stria crossover)
**Note that the anterior commissure carries sensory information from the MEDIAL olfactory stria
What is the primary portion of the olfactory cortex?
Piriform lobe
What is the entorhinal cortex?
Association cortex for olfactory information
In regards to olfaction, where does the thalamus project? What is the function of this area?
Orbitofrontal cortex–taste
What is the commissure that connects the two parts of the hippocampus?
Commissure of the fornix
What are the different parts of the hippocampus? What is an alternative name for the hippocampus?
- Pes hippocampus
- Hippoampus proper– CA 1, 2, 3
- Fornix
- Dentate Gyrus
- Subiculum
**The hippocampus is also known as the “Cornu ammonis”
Draw the path of flow through the hippocampus.
N/A
What are the different types of memory?
Working
Short-term
Long-term
Declarative
What is working memory?
Transient holding and processing of new and already stored information e.g. a phone number
What is short term memory?
This refers to a small amount of information in mind in an active, readily available state for a short period of time e.g. facts retained for min or hours with some with reinforcement
What is long-term memory?
Memories stored for decades or life via cerebral association areas
What is declarative memory?
Declarative memory refers to memories that can be consciously recalled such as facts and knowledge; it falls into two main categories
- Semantics i.e. words/ facts
- Episodic memory i.e. what you did throughout the day
What is the function of the amygdala?
Attaching emotional significance to sensory stimuli
Where do the medial stria of the olfactory tracts project?
Septal nuclei of the limbic system
Where do the amygdala and olfactory cortex project?
Entorhinal complex or “olfactory association cortex”
Where does the entorhinal cortex project?
Hippocampus
What is unusual about the olfactory pathway?
Does not project directly to the thalamus
What tract connects the amygdala to the hippocampus? What tract connects the hippocampus to the hypothalamus?
Amygdala= stria terminalis Hippocampus= fornix
What is the recurrent pathway of the hippocampus? What is the proposed function of this pathway?
Subiculum–>entorhinal cortex
*****Possibly implicated in long term memory consolidation
What are the three main groups of nuclei in the amygdala?
1) Corticomedial
2) Basolateral
3) Central nuclei
What nuclei of the amygdala the “input gateway?”
Corticomedial
Basolateral
What nucleus of the amygdala is the “output gateway?”
Central
What are the four major inputs into the amygdala?
- Olfactory tracts
- Orbitofrontal cortex
- Cingulate cortex
- Somatosensory cortex
What are the two major output pathways from the amygdala?
1) Stria terminalis (hippocampus)
2) Ventral amygdalofugal (ventral striatum i.e. nucleus accumbens)
What areas have reciprocal connections with the septal area?
1) Amygdala
2) Hippocampus
3) Brainstem
4) Hypothalamus
5) Cingulate gyrus
What is the function of the septal area?
Pleasure/ reward
What is the function of olfactory input to the hippocampus that connects to the hypothalamus?
Visceral responses to odors
What is the function of the olfactory input on the orbitofrontal cortex?
Awareness of odors
What structure helps to fine-tune olfactory sensitivity?
Anterior commissure
What is the input gate to the hippocampus?
Dentate gyrus
What is the output gate of the hippocampus?
Subiculum
What region of the hippocampus is most vulnerable to anoxia & ischemia?
Internal fields of cells i.e. CA1, CA2, CA3
What region of the brain is believed to be the trigger zone for temporal epilepsy?
Internal fields of cells i.e. CA1, CA2, CA3
What is the function of the stria terminalis?
Reciprocal connection between the central nucleus of the amygdala with septal area and hypothalamus that modulates visceral responses
What does the ventroamygdalofugal pathway connect to?
Brainstem
Ventral striatum or nucleus accumbens
What is the function of the ventroamygdalofugal pathway?
Allows emotions to influence movements
What does damage to the amygdala result in?
- Inability to express appropriate behavioral & visceral responses to known stimuli
- Inability to learn these responses to new stimuli
- Loss of the ability to read facial expressions
What are the major inputs to the septal area?
Hippocampus via the forix
Amygdala via the stria terminalis
What is the major output of the septal area?
Medial forebrain bundle to:
- Hypothalamus
- Brainstem nuclei
What is the function of the septal area?
“Pleasure & reward”
Also, relation of emotions to respiratory, cardiovascular, and salivatory centers/ nuclei
What was the major problem with the Papez Circuit?
It did NOT include the amygdala as part of the limbic system
What part of the brain is the target for benzodiasepines?
Limbic System
What is an alternative name for Korsakoff Syndrome?
Anmestic Confabulatory Syndrome
What is the typical cause of Korsakoff Syndrome?
Thiamin (B1) deficiency seen in chronic alcoholism
What are the symptoms of Korsakoff Syndrome?
- Loss of recent memory compensated for by making up fictitious information to fill the gaps
What part of the brain has the most damage in Korsakoff Syndrome?
Medial dorsal nucleus of the thalamus
