The limbic system is a complex set of brain structures located deep within the brain. It includes the hippocampus, amygdala, hypothalamus, and other structures. The limbic system plays an important role in memory, emotion, learning, and autonomic functions. It has connections throughout the brain and acts as a gateway between the cerebral cortex and structures like the hypothalamus. Certain parts of the limbic system, like the hippocampus, are critical for forming and storing memories.

1. Limbic system
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Dr. musa Atazade

2. Limbic lobe - limbic system:
•The limbic lobe is a complex set of three C-shaped structures containing
both gray and white matter (next slide).
•It lies deep within the brain and includes portions of all the lobes of the
cerebral hemispheres. A myriad of fiber tracts connect the limbic lobe with
numerous deep nuclei and the olfactory apparatus to form the limbic
system.
•It has a central role in memory, learning, emotion, neuroendocrine
function, and autonomic activities.

4. Outer arc of limbic lobe:
also called the limbic gyrus
includes:
subcallosal area, cingulate gyrus, isthmus of
the cingulate gyrus, parahippocampal gyrus

5. Subcallosal area:
A cluster of small septal nuclei that lie immediately anterior to the paraterminal
gyrus and anterior commissure.
input from: multiple midbrain nuclei, substantia nigra, CA1, subiculum,
amygdala, lateral hypothalamus, cingulate gyrus, and mamillary bodies.
Output to : entire hippocampal formation, the habenula, hypothalamus,
thalamus, amygdala, mamillary bodies and the cerebral cortex.

6. Middle arc of limbic lobe:
•The middle arc (also referred to as Broca’s intralimbic gyrus)
consists of the paraterminal gyrus, the indusium griseum, and
the hippocampus.
•The paraterminal gyrus is wedged between the septal nuclei
and the anterior commissure. Posterior to the anterior
commissure is the hypothalamus.
•.

7. indusium griseum
•The indusium griseum, extending from
the paraterminal gyrus, consists of gray
matter and white matter tracts named
the medial and lateral longitudinal stria.
The indusium griseum is closely applied
to the superior surface of the corpus
callosum. Posteriorly, it courses around
the splenium and inferiorly merges with
the tail of the hippocampus

8. Inner arc of limbic lobe :
•mamillary bodies,
•fornix
•alveus
fimbria
•.

9. Fimbria and fornix
•The alveus and fimbria are the major efferent fibers tracts of the
hippocampus. Posteriorly, the fimbria form the crura of the
fornix that continue upward deep to the splenium of the corpus
callosum. As the two crura converge, a thin triangular sheet of
fibers passes to the opposite side to form the commissure of the
fornix. The crura merge as the body of the fornix, which
continues forward along the inferior edge of the septum
pellucidum and roof of the third ventricle.

10. fornix
•At the foramen of Monroe, the
fornix divides into two columns
which course inferiorly. Just superior
to the anterior commissure, the
columns divide into pre- and
postcommissural tracts. The
precommissural fibers connect to the
septal nuclei and anterior
hypothalamic nuclei. The
postcommissural fibers continue
inferiorly to end in the mamillary
bodies.

11. Hippocampus
•The hippocampus is a part of the middle arc of the limbic system. It is
located in the medial temporal lobe inferior to the choroidal fissure and
temporal horn. In the sagittal plane the hippocampus is a club-shaped
structure divided into three parts: head, body, and tail. The more anterior
head is marked by digitations and is also called the pes hippocampus. The
body is more cylindrical in shape, and the tail tapers posteriorly. The gray
matter of the hippo campus is an extension of the subiculum of the
parahippo- campal gyrus.

12. Hippocampus...
•In coronal plane the hippocampus
and parahippocampal gyrus form
an S-shaped configuration. The
hippocampus itself consists of two
interlocking C-shaped structures:
the cornu ammonis and the
dentate gyrus. Histologically, the
hippocampus is further divided
into four sections: CA1 to CA4

13. amygdala
•The amygdala is positioned
directly anterior to the pes
hippocampus and above the tip of
the temporal horn. The alveus and
fimbria, white matter tracts along
the superior surface of the
hippocampus, continue posteriorly
as the fornix and serve as the
major efferent pathways to the rest
of the brain

14. function
•The limbic system is associated with emotion and motivation.
The amygdala is known to attach emotional significance to
sensory input. Olfactory stimuli enter the limbic loops via the
entorhinal cortex of the parahippocampal gyrus. The limbic
system has a direct influence on neuroendocrine, autonomic, and
behavior mechanisms, and it also has a role in functions such as
fight or flight, homeostasis, self-maintenance, appetite, and
sexuality.

16. Gateway!
•As noted above, structures of the limbic system are
highly interconnected with the rest of the brain, and they
likely form a gateway for communication between the
cerebral cortex and the hypothalamus. This gateway
allows for cognitive processes to modify the affect of the
limbic system on hypothalamic functions

17. memory
•The hippocampus, fornix, and mamillary bodies have an integral role in
memory and learning.
•left anterior temporal lobectomies : Impaired verbal memory
•right temporal lobectomy : visual/spatial memory disturbances.

20. •Note the relation ship
between these terms:
•- parahippocampal
gyrus
•- uncus
•-isthmus of cingulate
gyrus
•- pyriform and
enthorinal cortex

23. amygdala

26. cingulum
•the cingulum is a
collection of white matter
fibers projecting from the
cingulate gyrus to the
entorhinal cortex in the
parahippocampal gyrus.

28. Parahippocampal gyrus
•Located in medial temporal lobe : The parahippocampal gyrus
•(= hippocampal gyrus) is a cortical gray matter that surrounds the hippocampus.
•Includes :
•- perirhinal cortex
•- entorhinal cortex = ERC
•IMPORTANT ROLE : memory encoding and retrieval
•ERC funnels highly processed information to the hippocampal formation and
serves as its major output pathway.

32. diencephalon
•The diencephalon is part of the prosencephalon (forebrain), which develops from the
foremost primary cerebral vesicle.
•The prosencephalon differentiates into a caudal diencephalon and rostral
telencephalon.
•The cerebral hemispheres develop from the sides of the telencephalon, each containing
a lateral ventricle.
•The diencephalon consists of structures that are lateral to the third ventricle, and
includes the thalamus, the hypothalamus, the epithalamus and the subthalamus

33. diencephalon
•The diencephalon consists of structures
that are lateral to the third ventricle, and
includes the thalamus, the hypothalamus,
the epithalamus and the subthalamus