The limbic system plays an important role in emotion, motivation, learning, and memory. It consists of brain structures located deep within the cerebral hemispheres and under the cortex. These structures include the hippocampus, amygdala, septum, cingulate gyrus, hypothalamus, and others. The limbic system is involved in many psychiatric conditions due to its role in emotion regulation, memory formation, and the stress response. Dysfunction of limbic structures and circuits can lead to disorders like anxiety, depression, schizophrenia, and epilepsy. The limbic system also mediates functions like olfaction, appetite, sleep, sexual behavior, and addiction.

1. THE LIMBIC SYSTEM AND ITS
PSYCHIATRIC ASPECTS
PRESENTER:DR. AKASH NEMA
GUIDE:DR. NISHIKANT THORAT
MODERATOR:DR. VANSHREE PATIL MA’AM

2. CONTENTS
1. HISTORY
2. ANATOMY
3. FUNCTIONAL CIRCUITS
4. FUNCTIONS
5. CLINICAL IMPLICATIONS

3. HISTORY
1. The term "limbic" - Latin word limbus, for "border" or "edge’
2. Paul Broca coined the term based on its physical location in
the brain
3. James Papez(American physician) described his anatomical
model of emotion, the Papez circuit
4. Hippocampus, Cingulate gyrus,Hypothalamus, Anterior
thalamic nuclei,and the interconnections
5. Paul D. MacLean proposed triune brain theory (three brain in one)-R-
complex (reptilian complex), the limbic system and the
neocortex

4. NEURAL CIRCUIT FOR EMOTION AS ORIGINALLY
PROPOSED BY JAMES PAPEZ

5. ANATOMY
• The brain regions that constitute the limbic system
are:
1.Limbic cortex
Cingulate gyrus
Parahippocampal gyrus
2.Hippocampal formation
The dentate gyrus
Hippocampus
Subicular Complex
3.Amygdala
4.Septal area
5.Hypothalamus

6. ANATOMY
Hippocampus:
Learning and
Memory
Amygdala:
Emotions and
Aggression
Hypothalamus:
Hunger, Thirst
Temperature Control
Thalamus:
Relay Center for Sensory
Information

7. ANATOMY
Drawing of the major anatomical structures of the
limbic system

8. ANATOMY
1.LIMBIC CORTEX
• The cingulate gyrus and the parahippocampal gyrus
• The cingulate gyrus, located dorsal to the corpus callosum,
includes several cortical regions that are heavily
interconnected with the association areas of the cerebral
cortex
• Posteriorly, it becomes continuous with the parahippocampal
gyrus, located in the medial temporal lobe
• Entorhinal cortex funnels highly processed cortical
information to the hippocampal formation

9. ANATOMY
2.HIPPOCAMPAL FORMATION
• Hippocampal formation in the temporal lobe has three
distinct zones:
1. The dentate gyrus
2. The hippocampus proper
3. The subiculum
• These zones are composed of adjacent strips of cortical tissue,
and fold over each other mediolaterally in a spiral fashion,
giving rise to a C-shaped appearance

10. ANATOMY
Dentate gyrus 3 layers:
1. Outer- acellular molecular layer
2. Middle- granule cells
3. Inner- polymorphic layer
Hippocampus is also a trilaminate structure
• Composed of molecular and polymorphic layers and a middle
layer of pyramidal neurons
• Hippocampus is divided into three distinct fields:-CA3,CA2,
and CA1, on the basis of cytoarchitecture(CA-cornu ammonis)

11. ANATOMY
Subicular complex- 3 components
1. The presubiculum,
2. The parasubiculum,
3. And the subiculum
• It serve as transition regions between the hippocampus and
the parahippocampal gyrus.

12. ANATOMY
CROSS-SECTIONAL VIEW OF THE HIPPOCAMPAL FORMATION

13. ANATOMY
INTRINSIC CONNECTIVITY OF HIPPOCAMPAL FORMATION

14. ANATOMY
3.AMYGDALA
1. Group of nuclei
2. Located in the medial temporal lobe just anterior to the
hippocampal formation
3. These nuclei form several distinct clusters:
 Basolateral Complex
 Centromedial Amygdaloid Group
 Olfactory Group, includes the cortical amygdaloid nuclei

15. ANATOMY
• Basolateral complex
1. Largest group
2. The basolateral nuclei are directly and reciprocally connected
with the temporal, insular, and prefrontal cortices
3. Like cortical regions, the basolateral complex shares
bidirectional connections with the medial dorsal thalamic
nucleus
4. And receives projections from the midline and intralaminar
thalamic nuclei
5. Neurons are pyramidal like and use excitatory
neurotransmitter

16. ANATOMY
• Centromedial amygdala:- two major
subdivisions
1. The central subdivision- central amygdaloid nucleus+lateral
portion of the bed nucleus of the stria terminalis
2. The medial subdivision-Composed of the medial amygdaloid
nucleus

17. ANATOMY
4.SEPTAL AREA
• Gray matter structure
• Above the anterior commissure
• The septal nuclei are reciprocally connected with the
1. Hippocampus
2. Amygdala
3. Hypothalamus and project to a number of structures in
the brainstem

18. ANATOMY
5.HYPOTHALAMUS
• Lies at the center of the limbic system
• Subdivided into three zones:
1. Supraoptic Region
2. Tuberal Region
3. Mammillary Region
• The three zones are divided on each side into medial and
lateral areas by the fornix.

19. ANATOMY

20. ANATOMY
NUCLEI IN THE MEDIAL HYPOTHALAMUS

21. FUNCTIONAL CIRCUITS OF LIMBIC
SYSTEM
• The major structures of the limbic system are interconnected
with each other and with other components of the nervous
system
• Sensory information from the cingulate, the orbital and
temporal cortices, and the amygdala is transmitted to the
entorhinal cortex of the parahippocampal gyrus and then to
the hippocampal formation

22. FUNCTIONAL CIRCUITS OF LIMBIC
SYSTEM
• After traversing the intrinsic circuitry of the hippocampal
formation, information is projected through the fornix either
to the anterior thalamus, which, in turn, projects to the limbic
cortex, or to the septal area and the hypothalamus
• These latter two regions provide feedback to the hippocampal
formation through the fornix
• In addition, the mammillary bodies of the hypothalamus
project to the anterior thalamus
• Finally, the hypothalamus and the septal area project to the
brainstem and the spinal cord

23. FUNCTIONAL CIRCUITS OF LIMBIC
SYSTEM
Functional circuit b/w hippocampul formation,
Thalamus,cerebral cortex and hypothalamus

24. FUNCTIONAL CIRCUITS OF LIMBIC
SYSTEM
• Sensory information, primarily from the association regions of the
prefrontal and temporal cortices, projects to the amygdala
• Output from the amygdala is conducted through two main
pathways
• A dorsal route, the stria terminalis, project primarily to the septal
area and the hypothalamus
• The second route, the ventral amygdalofugal pathway, terminate
in the septal area, the hypothalamus, and the medial dorsal
thalamic nucleus
• The medial dorsal nucleus, in turn, projects heavily to prefrontal
and some temporal cortical regions

25. FUNCTIONAL CIRCUITS OF LIMBIC
SYSTEM
Functional circuit b/w amygdala,hypothalamus
Prefrontal and temporal ass. cortices

26. FUNCTIONAL CIRCUITS OF LIMBIC
SYSTEM
• The ventral amygdalofugal pathway also projects to the
Nucleus accumbens (ventral striatum)
• The area where the head of the caudate nucleus fuses with
the putamen
• This region sends efferents to the ventral palladium, an
extension of the globus pallidus
• This area, in turn, projects to the medial dorsal thalamic
nucleus

27. FUNCTIONAL CIRCUITS OF LIMBIC
SYSTEM
• Both of these pathways reveal how the limbic system
is able to integrate the highly processed sensory and
cognitive information content of the cerebral cortical
circuitry with the hypothalamic pathways that
control autonomic and endocrine systems

28. FUNCTIONAL CIRCUITS OF LIMBIC
SYSTEM
Functional circuits b/w basal ganglia and limbic system

29. FUNCTIONS OF THE LIMBIC SYSTEM
OLFACTION
1. The limbic structures are closely related to the olfactory
cortex
2. Amygdala is involved in the emotional response to smell
3. Entorhinal cortex, is concerned with olfactory memories
APPETITE AND EATING BEHAVIOR
1. Amygdala plays a role in food choice and emotional
modulation of food intake
2. The lateral nucleus of the hypothalamus is the center for
control of feeding whereas the ventromedial nucleus
functions as the satiety center

30. FUNCTIONS OF THE LIMBIC SYSTEM
SLEEP AND DREAMS
1. The limbic system is one of the most active brain areas
during dreaming (PET and fMRI )
2. Ties together emotions and memory during REM sleep to
form the content of dreams
3. The suprachiasmatic nucleus of hypothalamus is the
circadian rhythm generator controlling the sleep-wake cycle
4. The ventrolateral preoptic nucleus (VLPO) of the
hypothalamus functions as a 'sleep switch', promoting sleep
5. The lateral hypothalamic area (LHA) contains orexinergic
neurons that promote wakefulness

31. FUNCTIONS OF THE LIMBIC SYSTEM
EMOTIONAL RESPONSES
1. Fear
• Fear responses are produced by the stimulation of the
hypothalamus and amygdala(fear learning)
• Imaging studies have shown that viewing fearful faces
activates the left amygdala
2. Rage and placidity
• The destruction of the ventromedial hypothalamic nuclei and
septal nuclei in animals may induce rage
• Bilateral destruction of the amygdala results in placidity

32. FUNCTIONS OF THE LIMBIC SYSTEM
3. Autonomic and endocrine responses to emotion
• The stimulation of the cingulate gyrus and hypothalamus can
elicit autonomic responses
• The massive sympathetic discharge during stress is called the
"flight or fright response
• Stress via cortical and limbic connections causes release of
corticotropin-releasing hormone (CRH) from the
paraventricular nuclei of the hypothalamus (mediates
endocrine and immune responses)
4. Sexual behavior
• Medial preoptic area of the hypothalamus is the central
control of male sexual behavior

33. FUNCTIONS OF THE LIMBIC SYSTEM

34. FUNCTIONS OF THE LIMBIC SYSTEM
• Addiction and motivation
1. The reward circuitry underlying addictive behavior includes
amygdala and nucleus accumbens.
2. The amygdala plays a central role in cue-induced relapse.
3. Relapse associated with cues, stress and a single dose of a drug of
abuse results in release of excitatory neurotransmitters in brain
areas like hippocampus and amygdala
• Social cognition
1. Limbic structures involved are the cingulate gyrus and amygdala

35. FUNCTIONS OF THE LIMBIC SYSTEM
• Memory
1. Amygdala, prefrontal cortex and medial temporal lobe,
is involved in consolidation and retrieval of emotional
memories
2. Hippocampus is critical for long-term, declarative
memory storage
3. Medial temporal lobe memory system and
Diencephalic memory system(dysfunction of this
circuit results in Korsakoff's syndrome)

36. CLINICAL IMPLICATIONS
1. DEMENTIA
• Degenerative changes in the limbic system (particularly Pick's
disease and Alzheimer's disease)
• Marked atrophy, most notably the dentate gyrus and
hippocampus.
• In Alzheimer's disease,the hippocampus and amygdala are
often severely involved
2. ANXIETY DISORDER
• may be the result of a failure of the anterior cingulate and
hippocampus to modulate the activity of the amygdala

37. CLINICAL IMPLICATIONS
3. SCHIZOPHRENIA
• Studies have shown reduced limbic volumes
• distortion of cortical neurons of layer II of the ERC
• decreased size of hippocampus
• reduced number of GABAergic cells in the cingulate and
anterior thalamus with glutamatergic excitotoxicity
• The other circuit involved is the basolateral circuit which
mediates the social cognition deficits in schizophrenia

38. CLINICAL IMPLICATIONS
4.AFFECTIVE DISORDER
• Studies have shown variation in the volumes of the
frontal lobes, basal ganglia, amygdala and hippocampus.
• Functional studies have revealed decreased prefrontal
and anterior cingulate activity
• Recently, researchers have posited that affective and
cognitive symptomatology represents dysfunction within
a network-the anterior limbic network

39. CLINICAL IMPLICATIONS
5.ADHD
• Enlarged hippocampus.
• Disrupted connections between the amygdala and
orbitofrontal cortex- contribute to behavioral disinhibition
6. KLUVER BUCY SYNDROME
• bilateral destruction of the amygdaloid body and inferior
temporal cortex
• characterized by visual agnosia, placidity,,hyperorality and
hypersexuality

40. CLINICAL IMPLICATIONS
7. KORSAKOFFS SYNDROME
• damage to mammillary bodies, dorsomedial nucleus of
thalamus and hypothalamus (diencephalic memory circuit)
• chronic prominent impairment of recent and remote
memory(recent > remote)
• Confabulation may be marked but is not invariably present
8. AUTISM
• Limbic structures involved cingulate gyrus and amygdala,
which mediate cognitive and affective processing

41. CLINICAL IMPLICATIONS
9. EPILEPSY
• Temporal lobe epilepsy is the most common epilepsy in adults and
is most often caused by hippocampal sclerosis
• Hippocampal sclerosis with involvement of amygdala and
parahippocampal gyrus mesial temporal sclerosis (MTS)
10. LIMBIC ENCEPHALITIS
• a paraneoplastic syndrome -carcinoma of the lung, breast and some
other primaries.
• primarily involves the hippocampus, amygdala, cingulate gyrus,
insula and orbitalfrontal cortex
• memory loss, dementia, involuntary movements and ataxia

42. REFERENCES
• Kaplan and Sadock‘s Comprehensive textbook of
psychiatry,10e
• Rajmohan V, Mohandas E. The Limbic system. Indian
J Psychiatry 2007;49:132-9.

43. THANK YOU