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54 Cards in this Set

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What are the 4 basic function categories of the limbic system?
1. Homeostatic functions including autonomic and neuroendocrine control
2. Olfaction
3. Memory
4. Emotions and drives

(HOME)
What are the main structures of the limbic system?
1. Limbic cortex
2. Hippocampal formation
3. Amygdala
4. Olfactory cortex
5. Diencephalon
6. Basal ganglia
7. Basal forebrain
8. Septal nuclei
9. Brainstem
What structures of the LIMBIC CORTEX are involved in the limbic system?
1. Parahippocampal gyrus
2. Cingulate gyrus
3. Medial orbitofrontal cortex
4. Temporal pole
5. Anterior insula
What structures of the HIPPOCAMPAL FORMATION are involved in the limbic system?
1. Dentate gyrus
2. Hippocampus
3. Subiculum
What structures of the DIENCEPHALON are involved in the limbic system?
1. Hypothalamus
2. Thalamus
a. Anterior nucleus
b. Mediodorsal nucleus
c. Internal medullary
lamina
3. Habenula
What structures of the BASAL GANGLIA are involved in the limbic system?
1. Ventral striatum
a. Nucleus accumens
b. Ventral caudate and
putamen
2. Ventral pallidum
From a simplistic standpoint, what are the 4 structures responsible for each of the 4 main functional categories of the limbic system?
1. Homeostasis - Hypothalamus
2. Olfaction - Olfactory cortex
3. Memory - Hippocampal formation
4. Emotions and drive - Amygdala
Collateral sulcus
Separates the parahippocampal gyrus from the rest of the temporal lobe
Rhinal sulcus
The anterior continuation of the collateral sulcus
Uncus
A bump visible on the anterior medial parahippocampal gyrus
Isthmus
Where the cingulate gyrus joins the parahippocampal gyrus posteriorly
What are the 3 main nuclei of the amygdala?
1. Corticomedial
2. Basolateral
3. Central nuclei
How is the BASAL GANGLIA involved in the limbic system?
Limbic inputs to the basal ganglia arrive at the a) VENTRAL STRIATUM and b) NUCLEUS ACCUMBENS - info. is then relayed via the VENTRAL PALLIDUM to the mediodorsal nucleus of the thalamus
How is the MEDIODORSAL NUCLEUS of the thalamus involved in the limbic system?
It projects limbic info. to the orbitofrontal and anterior cingulate limbic cortices.
How many layers does the hippocampal formation have?
3
Allocortex
- "other cortex"
- phylogenetically ancient forms of cortex that do not have 6 distinct layers
What are the 2 subcategories of allocortex?
1) Archicortex - "first" or "original cortex"

2) Paleocortex - "old cortex"
Where is the archicortex?
Hippocampal formation
Where is the paleocortex predominantly found?
In the periform cortex of the olfactory area
What is the MESOCORTEX?
The regions between 3- and 6-layered cortex, which forms a transitional cortex
- aka "middle cortex"
Where is the mesocortex?
In the limbic cortex of the parahippocampal gyrus and anterior inferior insula
What does the term CORTICOID AREAS mean?
Refers to regions of the simple cortex that overlie or merge with subcortical nuclei
What are examples of CORTICOID areas?
1. Amygdala
2. Substantia innominata
3. Septal region
Where is the AMYGDALA?
- It lies in the anteromedial TL.
- It overlaps the anterior end of the hippocampus
- It lies ventral to the tip of the temporal horn of the lateral vetricle
Where is the BASAL FOREBRAIN?
Just anterior and lateral to the hypothalamus, at the base of the frontal lobes near the midline.
What is the SUBSTANTIA INNOMINATA?
1. The entire basal forebrain or
2. A nucleus within the basal forebrain called the NUCLEUS BASALIS OF MEYNERT, which lies just vetral to the anterior commisure (see p. 767)
What does the NUCLEUS BASALIS do?
It contaqins cholinergic neurons that provide the major cholinergic innervation fo rthe entire cerebral cortex (see p. 594).
What are the primary nuclei of the BASAL FOREBRAIN?
1. Nucleus basalis
2. Olfactory tubercle
3. Ventral pallidum
4. Nucleus of the diagnoal band of Broca
5. Preoptic area
Where is the SEPTAL REGION?
Just dorsal to the basal forebrain, nhear the septum pellucidum
What are the main nuclei of the SEPTAL REGION?
1. Medial septal nucleus
2. Lateral septal nucleus
What does the MEDIAL SEPTAL NUCLEUS do?
It contains cholinergic neurons that PROJECT TO the hippocampal formation and may play a role in modulation of memory function.
What does the LATERAL SEPTAL NUCLEUS do?
1. It RECEIVES info. from the hippocampal formation
2. It has a large PROJECTION TO the medial septal nucleus completing the circuit.
What is the MEDIAL OLFACTORY STRIA?
It is part of the feedback loop of the anterior olfactory nucleus, which feeds info to both ipsilateral and contralateral olfactory bulbs.
What does atrophy of the anterior olfactory nucleus do?
- Impaired olfaction
- Seen in Alzheimer's
What is the LATERAL OLFACTORY STRIA?
It is the tract through with mitral and tufted cells of the olfactory bulb project directly to the primary olfactory cortex.
What two cortices make up the PRIMARY OLFACTORY CORTEX?
1. Piriform cortex
2. Periamygdaloid cortex
Where is the PRIMARY OLFACTORY CORTEX located?
Near the medial anterior tip of the TL
Besides the primary olfactory cortex, where do fibers of the olfactory tract project to?
1. The CORTICOMEDIAL NUCLEUS of the amygdala
2. OLFACTORY TUBERCLE located in the anterior perforated substance
Where does the PERIFORM CORTEX send information to?
1. Anterior entorhinal cortex (which plays a role in memory and may explain why smells can elicit vivid memories)
2. Orbitofrontal olfactory area - both directly and indirectly thru the entorhinal cortex or the mediodorsal nucleus of the thalamus
3. Basolateral amygdala
4. Lateral preoptic area
5. Nucleus of the diagonal band
What 3 main regions of the brain appear to be critical to memory formation, consolidation, and retrieval?
1. Medioal temporal lobe memory areas
2. Medial diencephalic memory areas
3. The white matter network connections between 1 & 2
What structures are involved in the MEDIAL TEMPORAL LOBE memory areas?
1. Hippocampal formation
2. Parahippocampal gyrus
What structures are involved in the MEDIAL DIENCEPHALIC memory areas?
1. Thalamic nuclei
a. Mediodorsal nucleus
b. Anterior nucleus
c. Internal medullary lamina
2. Mammillary bodies
3. Other diencephalic nuclei lining the 3rd vetnricle.
What are the 3 components of the HIPPOCAMPAL FORMATION?
1. Dentate gyrus
2. Hippocampus
3. Subiculum
What cortical areas are included in the parahippocampla gyrus?
1. Entorhinal cortex (anterior portion)
2. Parahippocampal cortex (posterior portion)
3. Perirhinal cortex (medial and lateral walls of the rhinal sulcus)
What does the entorhinal cortex do?
It serves as the major input and output relay between association cortex and the hippocampal formation.
Where does the main input to the hippocampal formation arrive from?
From the association cortex in the F, P-O, and T lobes, through the entorhinal cortex.
Where does association info go to before going to the entorhinal cortex?
To the perirhinal cortex and parahippocampal cortex (see p. 773 & 776)
Where is memory storage thought to take place?
In the association and primary cortices that allow a particular memory to be reactivated.
What are the important output pathways of the hippocampal formation?
1. The projection from the subiculum to the ENTORHINAL cortex and from there back to multimodal association cortex.

2. From the subiculum to the FORNIX, which carries outputs to the diencephalon and septal nuclei.
What structure allows communication between the hippocampi?
Hippocampal commissure (see p. 778)
How do the medial septal nucleus and the nucleus of the diagonal band influence the hippocampal formation?
They provide modulatory inputs via the fornix, arising from their cholinergic inputs.
What is the alveus?
A white matter layer on the ventricular surface of the hippocampus.

These are output fibers from the hippocampal formation. (see p. 774 & 778)
What are the 3 main targets of axons traveling forward in the fornix?
1. Medial and lateral mammillary nuclei
2. Lateral septal nucleus
3. Anterior thalamic nucleus
What is the Papez circuit?
A complete loop of structures in the limbic system.