Limbic System - Shorer

Question 1

What are the 3 circles of the limbic system?

What are their pathways?

Answer 1

1. Fornix & Inner Arc
   Begins at alveus, continues through fimbria of fonix, under corpus collosum, splits at anterior commissure, posterior commissural part (80%) empties behind the anterior commissure at the mamillary body, precommisural part (20%) empties into septal area.
2. Intralimbic gyrus
   Starts at dentate gyrus above hippocampus and jumps above the corpus callosum and terminates at septal area. Medial and lateral longitudinal striae above the corpus collosum. Covered by indusium griseum.
3. Limbic gyrus
   Around corpus collosum. Anterior: paraterminal gyrus. Below corpus collosum is subcollosal gyrus. Large gyrus: gyrus cinguli. Back portion: isthmus. Parahypocampal gyrus, Uncus.

Question 2

What and where is the hypothalamic sulcus?

Answer 2

Below the thalamus and above the hypothalamus within the third ventricle behind the ependyma, the cortex and the white matter.

Question 3

What is the striae terminalis?

Answer 3

Outgoing information from the amygdaloid complex. Bundle of fibers goes along inferior border of lateral ventricle to septal area. In the groove between the caudate nucleus and the thalamus.

Question 4

How is the olfactory bulb connected to the cortex and the amygdala?

Answer 4

At cortex there is interpretation of sensory stimulation. From olfactory bulb directly to uncus is the sensory cortex of olfactory stimulation. Other fibers from olfactory terminate at the amygdala. These paths don’t deal with smell interpretation (this is in the cortex). Amygdala deals with response to the smell: judgement as good, gross, emotional feeling relating to it. Response without knowing the type of smell. Connection from amygdaloid process to brainstem: VTA (ventral tegmental area), connects the amygdaloid with lower regions of the autonomic responses. Amygdaloid also connects to the hypothalamus. Tiny fibers connect lower region to CNS.