The limbic system and reticular formation are brain structures involved in emotion, learning, memory, and behavior. The limbic system includes the hippocampus, amygdala, and surrounding cortical areas. It regulates emotions, expression of feelings, fear responses, and memory formation. The reticular formation is a diffuse network in the brainstem that maintains arousal, muscle tone, sleep-wake cycles, and modulates pain perception. Together these structures form circuits that are important for basic functions and are implicated in various psychiatric conditions.

1. LIMBICLIMBIC
SYSTEMSYSTEM
&&
RETICULARRETICULAR
FORMATIONFORMATION

2. LEARNING OBJECTIVESLEARNING OBJECTIVES

3. I.I. Anatomical Location + discussion ofAnatomical Location + discussion of
components.components.
II.II. Structure and function of theStructure and function of the
hippocampal formation.hippocampal formation.
III.III. The Amygdaloid nucleus complex andThe Amygdaloid nucleus complex and
the function of its 3 components.the function of its 3 components.
IV.IV. Links between the limbic system andLinks between the limbic system and
effector (behaviour) systems.effector (behaviour) systems.
V.V. Links between neurotransmitter-Links between neurotransmitter-
specific projection systems and thespecific projection systems and the
limbic system.limbic system.
VI.VI. Regional Anatomy of these structures.Regional Anatomy of these structures.

4. LIMBIC SYSTEMLIMBIC SYSTEM

5. I.I. Anatomical Location and Overview.Anatomical Location and Overview.
A.A. Limbic association cortex –Limbic association cortex –
surrounding diencephalonsurrounding diencephalon
-medial + inferior (orbital) surface-medial + inferior (orbital) surface 
cingulate gyrus, parahippocampalcingulate gyrus, parahippocampal
gyrus, orbital gyrus, temporal pole.gyrus, orbital gyrus, temporal pole.

8. FUNCTIONSFUNCTIONS
EmotionsEmotions
(Expression of Feelings)(Expression of Feelings)
FEAR(Fight or Flight))FEAR(Fight or Flight))
BehaviorBehavior
MemoryMemory

9.  Anatomically refers to areasAnatomically refers to areas
surroundingsurrounding the diencephalon (limbus =the diencephalon (limbus =
border) and bordering the cerebralborder) and bordering the cerebral
cortex.cortex.
 In 1878 Broca introduced the nameIn 1878 Broca introduced the name
LIMBIC SYSTEMLIMBIC SYSTEM

10.  The “C”-shaped hippocampal formationThe “C”-shaped hippocampal formation
and includes the amygdala, cingulateand includes the amygdala, cingulate
and parahippocampal cortices.and parahippocampal cortices.
The key to learning, memory, andThe key to learning, memory, and
behavior (including emotional behavior)behavior (including emotional behavior)
– of paramount importance in– of paramount importance in
psychiatry.psychiatry.

11. ANATOMICAL COMPONENTSANATOMICAL COMPONENTS
 Olfactory pathwayOlfactory pathway
 Pyriform lobePyriform lobe
 Amygdaloid bodyAmygdaloid body
 Hippocampal formationHippocampal formation
 Limbic lobeLimbic lobe

12.  Hypothalamus, AN thalamus, habenularHypothalamus, AN thalamus, habenular
N, interpeduncular N, midbrain tegmentalN, interpeduncular N, midbrain tegmental
N, strai medullaris thalami, fasciculusN, strai medullaris thalami, fasciculus
retroflexus & median forebrain bundleretroflexus & median forebrain bundle

13. LIMBIC LOBELIMBIC LOBE

14. Limbic System: Cortical Areas
Figs. 16-2 and 3
Note: surrounding
diencephalon, medial +
inferior (orbital) surface 
[cinglulate gyrus, parahipp
gyrus, orbital gyrus,
temporal pole].
These cortices are near other
association cortices and project
to:

15. B. the Hippocampal Formation and Amygdala.
The “C” shape, along with the major output paths
for the hippocampus: the fornix.

16. CORTICAL & SUBCORTICALCORTICAL & SUBCORTICAL
STRUCTURES FORMINGSTRUCTURES FORMING
LIMBIC SYSTEMLIMBIC SYSTEM

17. Look!!

18. Limbic SystemLimbic System
 The limbic system isThe limbic system is
comprised ofcomprised of
– Hippocampus: involved inHippocampus: involved in
learning and memorylearning and memory
– Amygdala: involved inAmygdala: involved in
emotionemotion
– Mammillary BodiesMammillary Bodies
 TheThe fornixfornix is a fiber bundleis a fiber bundle
that interconnects thethat interconnects the
hippocampus with thehippocampus with the
mammillary bodiesmammillary bodies

19. The Limbic SystemThe Limbic System

25. PAPEZ CIRCUITPAPEZ CIRCUIT

26. PAPEZ CIRCUITPAPEZ CIRCUIT
 Papez circuit consists of hippocampus,Papez circuit consists of hippocampus,
fornix, mammillothalamic tract, anteriorfornix, mammillothalamic tract, anterior
thalamic nuclei, thalamocingular radiation,thalamic nuclei, thalamocingular radiation,
cingulate gyrus and cingulohippocampalcingulate gyrus and cingulohippocampal
fibersfibers

27. SUBCORTICAL REGIONSUBCORTICAL REGION
(Limbic)(Limbic)

28. AMYGDALAAMYGDALA

29.  Superiorly it is related to the anterior partSuperiorly it is related to the anterior part
of lentiform nucleus.of lentiform nucleus.
 Inferiorly it is related to uncus.Inferiorly it is related to uncus.
 Medially it extends to the inferior surfaceMedially it extends to the inferior surface
of the cortex of the temporal lobe.of the cortex of the temporal lobe.

30.  The dorsomedial part of amygdaloid bodyThe dorsomedial part of amygdaloid body
is connected with the primary olfactoryis connected with the primary olfactory
area while venteromedial part isarea while venteromedial part is
component of limbic system.component of limbic system.
 Feeling of fear & apprehension leading toFeeling of fear & apprehension leading to
aggressionaggression

31. CONNECTIONS OFCONNECTIONS OF
AMYGDALAAMYGDALA

32. SEPTAL AREASEPTAL AREA

33.  The cortex of the septal region is presentThe cortex of the septal region is present
infront of lamina terminalis beneath theinfront of lamina terminalis beneath the
genu & rostrum of corpus callosum.genu & rostrum of corpus callosum.
 The paraolfactory area or the subcallosalThe paraolfactory area or the subcallosal
gyrus lies underneath the rostrum ofgyrus lies underneath the rostrum of
corpus callosum.corpus callosum.
 Posterior to parolfactory area & justPosterior to parolfactory area & just
anterior to lamina terminalis isanterior to lamina terminalis is
paraterminal gyrusparaterminal gyrus

35. CLINICAL ANATOMYCLINICAL ANATOMY
 Alzheimers DiseaseAlzheimers Disease
 Papez circuitPapez circuit
 Brucy Calvier SyndromeBrucy Calvier Syndrome
 EpilepsyEpilepsy
 DementiaDementia

36. Feelings & EmotionsFeelings & Emotions
(Emotion is expression of feelings(Emotion is expression of feelings
andand Antiemotions is Depression)Antiemotions is Depression)
 Nature controls Man by two things Pain and PleasureNature controls Man by two things Pain and Pleasure
(Patient =Suffering)(Patient =Suffering)
Pain is PunishmentPain is Punishment
Pleasure is RewardPleasure is Reward
FEAR (DANGER):Horror,HauntedFEAR (DANGER):Horror,Haunted
FightFight
FrightFright
HypothalamusHypothalamus
SympatheticSympathetic
EndocrineEndocrine
Amygdaloid damage- ends Fear (Fearless)Amygdaloid damage- ends Fear (Fearless)

37. Food & SexFood & Sex
 Nature`s Priorities (Biological needs)areNature`s Priorities (Biological needs)are
 Preservation of life(Food)Preservation of life(Food)
 Procreation of life(Sex)Procreation of life(Sex)
 Human hasHuman has
 self conciousness(I)self conciousness(I)
 emotionsemotions
 memorymemory
 Damage to Amygdaloid leads to abnormal foodDamage to Amygdaloid leads to abnormal food
habits & Sex (Hypersexualty)habits & Sex (Hypersexualty)

38. MemoryMemory(Storage of information(Storage of information))
 Alzheimers DiseaseAlzheimers Disease
 HIPPOCAMPAL DAMAGE CAUSESHIPPOCAMPAL DAMAGE CAUSES
LOSS OF RECENT MEMORYLOSS OF RECENT MEMORY

39. RETICULAR FORMATIONRETICULAR FORMATION

40.  Diffuse network of nerve fibers & neuronsDiffuse network of nerve fibers & neurons
 In tegmental core throughout brainstem.In tegmental core throughout brainstem.
 Fills space not occupied by cranial nerveFills space not occupied by cranial nerve
nuclei/ other nuclei/ tracts.nuclei/ other nuclei/ tracts.

41. FUNCTIONFUNCTION
 Concerned with arousal or alertness byConcerned with arousal or alertness by
ARASARAS
 Maintains muscle tone & posture duringMaintains muscle tone & posture during
sitting and standing by reticulospinal tractsitting and standing by reticulospinal tract
 Seratonergic fibers induce slow sleep &Seratonergic fibers induce slow sleep &
dimnish pain sensationdimnish pain sensation
 Nadr. fibers produce paradoxical sleepNadr. fibers produce paradoxical sleep
 Dopaminergic fibers preventsDopaminergic fibers prevents
parkinsonian tremor & rigidityparkinsonian tremor & rigidity

42.  TS through brainstem & spinal cordTS through brainstem & spinal cord
showing the reticular formationshowing the reticular formation

45. EXTENT OF RETICULAREXTENT OF RETICULAR
FORMATIONFORMATION SUPERIORLY:SUPERIORLY:
 Reticular nucleus &Reticular nucleus &
subthalamic nuclleussubthalamic nuclleus
 INFERIORLY :INFERIORLY :
 Cervical spinal cordCervical spinal cord

46. RETICULAR NUCLEI INRETICULAR NUCLEI IN
BRAINSTEMBRAINSTEM

48. EFFERENT & AFFERENTEFFERENT & AFFERENT
CONNECTIONSCONNECTIONS

52. Various nuclear regions inVarious nuclear regions in
reticular formation between wellreticular formation between well
defined cranial nerve nucleidefined cranial nerve nuclei

53. ASCENDING RETICULARASCENDING RETICULAR
ACTIVATING SYSTEMACTIVATING SYSTEM
 Ascending fibers of reticular formation toAscending fibers of reticular formation to
cerebral cortex and limbic systemcerebral cortex and limbic system
 Convey diffuse input from all sensoryConvey diffuse input from all sensory
systemssystems
 Concerned with degree of conciousnessConcerned with degree of conciousness
from sleep to arousalfrom sleep to arousal