Flashcards in export_hippocampal formation Deck (22)
What are the components of the limbic system
1. Limbic cortex
2. Subcortical limbic structures
What are the subcomponents of the limbic cortex
1. Parahippocampal gyrus
2. Hippocampal formation
3. Dentate gyrus
4. Cingulate gyrus
6. Orbitofrontal gyrus
What are the subcortical limbic structures involved in the limbic system
3. Septal nuclei
4. Habenular nuclei
5. Anterior and dorsomedial thalamic nuclei
6. Indusium griseum
What are the fibers/tracts involved in the limbic system
1. Mamillothalamic tract
3. Stria medullaris thalami
4. Stria terminalis
What are the layers of the hippocampus
5. Dentate gyrus
All of these layers are archipallum, that is they are composed of three layers - molecular, pyramidal and polymorphic.
The inferior parahippocampal gyrus is what type or cortex?
Isocortex - it has 6 layers.
What is the indusium griseum
Hippocampal remnants that course over the dorsal surface of the corpus callosum and connect the septal area with the hippocampus.
Composed of the subcallosal gyrus and the medial and lateral longitudinal striae.
Input to the hippocampal gyrus
1. Entorhinal cortex --> hippocampal and dentate gyrus.
2. Medial septal nucleus --> Fimbria
3. Cingulate gyrus --> cingulum --> presubiculum/entorrhinal cortex --> hippocampus
What are the components of the fornix
What are the output fibers/tracts located within the fornix
1. Precommissural fornix --> caudate septal nucleus
2. Postcommissural fornix --> mammillary bodies --> anterior thalamic nulcei --> cingulate gyrus
3. Subiculum --> postcommissural fornix ---> various structures.
Hippocampal output from the subiculum leaves via the postcommissural fornix and travels to the 5 following structures:
1. Mammillary bodies
2. Anterior thalamic nuclei
3. Lateral septal area of the hypothalamus
4. Medial frontal cortex
5. Cingulate gyrus
What is the sole direct cortical projector/output of the hippocampus
The subiculum. Dentate fibers do not leave the hippocampus.
CA1 pyramidal cell axons project to the
Subiculum and fornix
CA3 pyramidal cell axons project to the
CA1 and fornix
What is the function of the hippocampus
Consolidation of short-term memory into long-term memory. Unilateral injury to mammillary bodies or the fornix does not seem to impair function but lesions to this area may cause psychomotor seizures.
What is the circuit of Papez
A bidirectional connection from the subiculum--> mammillary bodies --> mammillothalamic tract --> anterior thalamic nucleus --> entorhinal cortex --> subiculum.
Involved with emotion.
What are inputs to the amygdala
1. Locus ceruleus - noradrenergic fibers
2. SN and ventral tegmentum - dopaminergic fibers
3. Substantia innominata and lateral olfactory area - cholinergic fibers
4. Raphe nucleus - serotonergic fibers
What are the main outputs of the amygdala?
1. Stria terminalis --> nucleus of the stria terminalis --> hypothalamus
2. Ventral amygdalofugal tract --> to various areas including the brainstem nuclei to regulate autonomic functions dealing with fear or stress.
4. Amygdalostriate --> nucleus accumbens
What is the other name for the substantia innominate and where is it located
Nucleus basalis of Meynert
It is located in the basal forebrain and extends from the olfactory tubercle to the hypothalamus
What is the input and output of the substantia innominate/nucleus basalis of Meynert
Input: amygdala, temporal lobe, pyriform cortex, and entorhinal cortex.
Output: Diffuse cortical outputs.
Features of the substantia innominata
High concentration of cholinergic fibers and the sole source of the cholinergic output to the cortex.
These cells degenerate in the setting of Alzheimer's disease