LIMBIC SYSTEM LIMBIC SYSTEM

&& RETICULAR RETICULAR FORMATIONFORMATION

LEARNING OBJECTIVESLEARNING OBJECTIVES

I.I. Anatomical Location + discussion of Anatomical Location + discussion of components.components.

II.II. Structure and function of the Structure and function of the hippocampal formation.hippocampal formation.

III.III. The Amygdaloid nucleus complex and The Amygdaloid nucleus complex and the function of its 3 components.the function of its 3 components.

IV.IV. Links between the limbic system and Links between the limbic system and effector (behaviour) systems.effector (behaviour) systems.

V.V. Links between neurotransmitter-Links between neurotransmitter-specific projection systems and the specific projection systems and the limbic system.limbic system.

VI.VI. Regional Anatomy of these structures.Regional Anatomy of these structures.

LIMBIC SYSTEMLIMBIC SYSTEM

I.I. Anatomical Location and Anatomical Location and Overview.Overview.

A.A. Limbic association cortex – Limbic association cortex – surrounding diencephalonsurrounding diencephalon-medial + inferior (orbital) surface -medial + inferior (orbital) surface cingulate gyrus, cingulate gyrus, parahippocampal gyrus, orbital parahippocampal gyrus, orbital gyrus, temporal pole.gyrus, temporal pole.

FUNCTIONSFUNCTIONS EmotionsEmotions(Expression of Feelings)(Expression of Feelings)FEAR(Fight or Flight))FEAR(Fight or Flight))BehaviorBehaviorMemoryMemory

Anatomically refers to areas Anatomically refers to areas surroundingsurrounding the diencephalon the diencephalon (limbus = border) and bordering (limbus = border) and bordering the cerebral cortex. the cerebral cortex.

In 1878 Broca introduced the name In 1878 Broca introduced the name LIMBIC SYSTEMLIMBIC SYSTEM

The “C”-shaped hippocampal The “C”-shaped hippocampal formation and includes the formation and includes the amygdala, cingulate and amygdala, cingulate and parahippocampal cortices.parahippocampal cortices.

The key to learning, memory, and The key to learning, memory, and behavior (including emotional behavior (including emotional behavior) – of paramount behavior) – of paramount importance in psychiatry.importance in psychiatry.

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

Hypothalamus, AN thalamus, Hypothalamus, AN thalamus, habenular N, interpeduncular N, habenular N, interpeduncular N, midbrain tegmental N, strai midbrain tegmental N, strai medullaris thalami, fasciculus medullaris thalami, fasciculus retroflexus & median forebrain retroflexus & median forebrain bundlebundle

LIMBIC LOBELIMBIC LOBE

Limbic System: Cortical AreasFigs. 16-2 and 3

Note: surroundingdiencephalon, medial +inferior (orbital) surface [cinglulate gyrus, parahippgyrus, orbital gyrus, temporal pole].

These cortices are near otherassociation cortices and projectto:

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

CORTICAL & SUBCORTICAL CORTICAL & SUBCORTICAL STRUCTURES FORMING STRUCTURES FORMING

LIMBIC SYSTEMLIMBIC SYSTEM

Look!!

Limbic SystemLimbic System The limbic system is The limbic system is

comprised ofcomprised of– Hippocampus: involved Hippocampus: involved

in learning and memoryin learning and memory– Amygdala: involved in Amygdala: involved in

emotionemotion– Mammillary BodiesMammillary Bodies

TheThe fornix fornix is a fiber is a fiber bundle that interconnects bundle that interconnects the hippocampus with the hippocampus with the mammillary bodiesthe mammillary bodies

The Limbic SystemThe Limbic System

PAPEZ CIRCUITPAPEZ CIRCUIT

PAPEZ CIRCUITPAPEZ CIRCUIT Papez circuit consists of Papez circuit consists of

hippocampus, fornix, hippocampus, fornix, mammillothalamic tract, anterior mammillothalamic tract, anterior thalamic nuclei, thalamocingular thalamic nuclei, thalamocingular radiation, cingulate gyrus and radiation, cingulate gyrus and cingulohippocampal fiberscingulohippocampal fibers

SUBCORTICAL REGION SUBCORTICAL REGION (Limbic)(Limbic)

AMYGDALAAMYGDALA

Superiorly it is related to the anterior Superiorly it is related to the anterior part of lentiform nucleus. part of lentiform nucleus.

Inferiorly it is related to uncus. Inferiorly it is related to uncus. Medially it extends to the inferior Medially it extends to the inferior

surface of the cortex of the temporal surface of the cortex of the temporal lobe. lobe.

The dorsomedial part of amygdaloid The dorsomedial part of amygdaloid body is connected with the primary body is connected with the primary olfactory area while venteromedial olfactory area while venteromedial part is component of limbic system.part is component of limbic system.

Feeling of fear & apprehension Feeling of fear & apprehension leading to aggressionleading to aggression

CONNECTIONS OF CONNECTIONS OF AMYGDALAAMYGDALA

SEPTAL AREASEPTAL AREA

The cortex of the septal region is present The cortex of the septal region is present infront of lamina terminalis beneath the infront of lamina terminalis beneath the genu & rostrum of corpus callosum. genu & rostrum of corpus callosum.

The paraolfactory area or the subcallosal The paraolfactory area or the subcallosal gyrus lies underneath the rostrum of gyrus lies underneath the rostrum of corpus callosum. corpus callosum.

Posterior to parolfactory area & just Posterior to parolfactory area & just anterior to lamina terminalis is anterior to lamina terminalis is paraterminal gyrusparaterminal gyrus

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

Feelings & EmotionsFeelings & Emotions(Emotion is expression of feelings(Emotion is expression of feelings and and Antiemotions is Depression)Antiemotions is Depression)

Nature controls Man by two things Pain and Nature controls Man by two things Pain and PleasurePleasure

(Patient =Suffering)(Patient =Suffering)Pain is Punishment Pain is Punishment Pleasure is RewardPleasure is RewardFEAR (DANGER):Horror,HauntedFEAR (DANGER):Horror,Haunted Fight Fight FrightFright HypothalamusHypothalamus SympatheticSympathetic EndocrineEndocrine Amygdaloid damage- ends Fear (Fearless)Amygdaloid damage- ends Fear (Fearless)

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 Damage to Amygdaloid leads to abnormal

food habits & Sex (Hypersexualty)food habits & Sex (Hypersexualty)

MemoryMemory(Storage of (Storage of informationinformation))

Alzheimers DiseaseAlzheimers Disease HIPPOCAMPAL DAMAGE CAUSES HIPPOCAMPAL DAMAGE CAUSES

LOSS OF RECENT MEMORYLOSS OF RECENT MEMORY

RETICULAR FORMATIONRETICULAR FORMATION

Diffuse network of nerve fibers & Diffuse network of nerve fibers & neuronsneurons

In tegmental core throughout In tegmental core throughout brainstem.brainstem.

Fills space not occupied by cranial Fills space not occupied by cranial nerve nuclei/ other nuclei/ tracts.nerve nuclei/ other nuclei/ tracts.

FUNCTIONFUNCTION Concerned with arousal or alertness by Concerned with arousal or alertness by

ARASARAS Maintains muscle tone & posture during Maintains 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 prevents Dopaminergic fibers prevents

parkinsonian tremor & rigidity parkinsonian tremor & rigidity

TS through brainstem & spinal cord TS through brainstem & spinal cord showing the reticular formationshowing the reticular formation

EXTENT OF RETICULAR EXTENT OF RETICULAR FORMATIONFORMATION

SUPERIORLY:SUPERIORLY: Reticular nucleus & Reticular nucleus &

subthalamic nuclleussubthalamic nuclleus

INFERIORLY :INFERIORLY : Cervical spinal cordCervical spinal cord

RETICULAR NUCLEI IN RETICULAR NUCLEI IN BRAINSTEMBRAINSTEM

EFFERENT & AFFERENT EFFERENT & AFFERENT CONNECTIONSCONNECTIONS

Various nuclear regions in Various nuclear regions in reticular formation between reticular formation between well defined cranial nerve well defined cranial nerve

nucleinuclei

ASCENDING RETICULAR ASCENDING RETICULAR ACTIVATING SYSTEMACTIVATING SYSTEM

Ascending fibers of reticular Ascending fibers of reticular formation to cerebral cortex and formation to cerebral cortex and limbic systemlimbic system

Convey diffuse input from all sensory Convey diffuse input from all sensory systemssystems

Concerned with degree of Concerned with degree of conciousness from sleep to arousalconciousness from sleep to arousal