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The Limbic System. The Limbic System. The Limbic System. In 1878, Paul Broca defined the limbic (Latin limbus :border ) lobe as the cerebral convolutions that surround the brain stem and central commissures consisting primarily of the parahippocampal and cingulate gyri .

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The limbic system
The Limbic System

The limbic system1
The Limbic System

The Limbic System

  • In 1878, Paul Broca defined the limbic (Latin limbus:border) lobe as the cerebral convolutions that surround the brain stem and central commissures consisting primarily of the parahippocampal and cingulategyri.

  • In 1937, Papez suggested the limbic lobe was part of a larger integrated system involved in emotional behavior that is now referred to as the limbic system. 

  • Different authors have defined its components in various ways, but the main structures include the cingulategyrus, the parahippocampalgyrus, the hippocampal formation, the hypothalamus, the septal nucleus, the amygdala, the mammillary bodies, several thalamic nuclei, the basal forebrain, olfactory structures, and the subcallosal region as well the tracts connecting them.

The limbic system2
The Limbic System

The limbic system3
The Limbic System

  • First it includes several regions of one form of cortex called the limbic cortex; this cortex is also known as the cingulate cortex as shown in the picture.

  • Besides the limbic cortex, the most important parts of the limbic system are the hippocampus and the amygdala.  The fornix and mammilary bodies are also parts of the limbic system.

  • The limbic system has been implicated in learning and memory and emotions.  The implication in emotions involves feelings and expressions of emotions, emotional memories and recognition of emotions in other people.

The limbic system4
The Limbic System

  • The limbic system (or paleomammalian brain) is a complex set of brain structures that lies on both sides of the thalamus, right under the cerebrum.

  • It is not a separate system, but a collection of structures from the cerebrum, diencephalon, and midbrain, including the:

    • Hippocampus

    • Amygdalae

    • Anterior thalamic nuclei

    • Septum,

    • Limbic cortex

    • Fornix

The limbic system5
The Limbic System

  • It supports a variety of functions, including:

    • Emotion

    • Behavior

    • Motivation

    • Long-term memory

    • Olfaction.

  • It appears to be primarily responsible for our emotional life, and has a great deal to do with the formation of memories.

The limbic system6
The Limbic System

The limbic system7
The Limbic System

The limbic system8
The Limbic System

The limbic system9
The Limbic System

The limbic system10
The Limbic System

The limbic system11
The Limbic System

  • Anatomy

  • The limbic system is the set of brain structures that forms the inner border of the cortex.

  • The components of the limbic system located in the cerebral cortex generally have fewer layers than the classical 6-layered neocortex, and are usually classified as allocortex or archicortex.

  • The limbic system includes many structures in the cerebralpre-cortex and sub-cortex of the brain. The term has been used within psychiatry and neurology, although its exact role and definition have been revised considerably since the term was introduced.

  • The following structures are, or have been considered to be, part of the limbic system:

The limbic system12
The Limbic System

  • Hippocampus:

    • Required for the formation of long-term memories and implicated in maintenance of cognitive maps for navigation.

    • The hippocampus consists of two “horns” that curve back from the amygdalae.

    • It appears to be very important in converting things that are “on one's mind” at the moment (in short-term memory) into things that one will remember for the long run (long-term memory).

    • If the hippocampus is damaged, a person cannot build new memories and lives instead in a strange world where everything he or she experiences just fades away, even while older memories from the time before the damage are untouched.

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The Limbic System

  • Amygdala:

  • Involved in signaling the cortex of motivationally significant stimuli such as those related to reward and fear in addition to social functions such as mating.

  • Furthermore, the anatomy of amygdalae are two almond-shaped masses of neurons on either side of the thalamus at the lower end of the hippocampus.

  • The amygdalae stimulate the hippocampus to remember many details surrounding the situation, as well.

The limbic system14
The Limbic System

  • Fornix:

    • is a C shaped bundle of axon which carries signals from the hippocampus to the mammillary bodies and septal nuclei.

  • Mammillary body:

    • Locates at the ends of the anterior arches of the fornix. It is involved with the process of recognition memory.

  • Septal nuclei:

  • Located anterior to the interventricular septum, the septal nuclei provide critical interconnections. The septal area isn't related to the smell, but it is the pleasure zone in animals.

The limbic system15
The Limbic System

Mammillary Body:a small, round, paired cell group that protrudes into the interpeduncularfossa from the inferior aspect of the hypothalamus. It receives hippocampal fibers through the fornix and projects fibers to the anterior thalamic nuclei and into the brainstem tegmentum.

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The Limbic System

  • Limbic lobe

    • Parahippocampalgyrus:

      • Plays a role in the formation of spatial memory.

    • Cingulategyrus:

      • Autonomic functions regulating heart rate, blood pressure and cognitive and attentional processing.

    • Dentate gyrus:

      • Thought to contribute to new memories.

The limbic system17
The Limbic System

  • In addition, these structures are sometimes also considered to be part of the limbic system:

    • Entorhinal cortex: Important memory and associative components.

    • Piriformcortex:The function of which relates to the olfactory system.

    • Fornicate gyrus: Region encompassing the cingulate, hippocampus, and parahippocampalgyrus.

    • Nucleus accumbens: Involved in reward, pleasure, and addiction.

    • Orbitofrontal cortex: Required for decision making.


  • Fornix:

  • The major efferent fiber tract arising from the hippocampal formation.

  • It is the direct continuation of the alveus and the fimbria.

  • Below the splenium of the corpus callosum, these structures become the crus of the fornix.

  • Under the body of the corpus callosum, the two crura fuse to become the body of the fornix which is attached to the corpus callosum superiorly by the septum pellucidum.


  • Anteriorly, the body turns ventrally in front of the interventricular foramina and splits into right and left half.

  • These vertical portions are referred to as the columns of the fornix. The main portion of the columns (postcommissural fornix) pass inferiorly through the hypothalamus and terminate in the mammillary bodies.

  • A small portion of the columns (precommissural fornix) split off above the anterior commissure and terminate anteriorly in the septal nuclei.

Hippocampus and fornix
Hippocampus and Fornix

Uncus:a prominent bulge on the medial surface of the temporal lobe.

The bulge contains the medial portion of two structures: anteriorly the amygdala and posteriorly the peshippocampi.

These structure are separated by the most anterior portion of the temporal horn of the lateral ventricle which is lies horizontally in a coronal plane.

The uncus is part of the parahippocampalgyrus.

The papez circuit
The Papez Circuit

  • The Papez circuit is a neural pathway in the brain first described by American neuroanatomistJames Papezin 1937.

  • Papez believed that the circuit was involved with emotions.

  • Since the circuit's discovery, many experiments have been conducted to explore the system and how its structures work together.

  • Recent studies show that it has a more significant role in memory functions than in emotions.

  • The Papez circuit was later modified by American neuroscientist and physician Paul D. MacLean and now, the circuit is known as the limbic system.

  • Damage to parts of the Papez circuit have shed light on not only its function, but on possible diagnosis of many disorders relating to memory.

The papez circuit1
The Papez Circuit

  • The Papez circuit involves various structures of the brain.

  • It begins and ends with the hippocampus (or the hippocampal formation). Fiber dissection indicates that the average size of the circuit is 350 milimeters. The Papez circuit goes through the following neural pathway:

  • hippocampal formation (subiculum) → fornix → mammillary bodies → mammillothalamic tract → anterior thalamic nucleus → cingulum → entorhinal cortex → hippocampal formation.

  • A photograph of the inferior medial view of the brain when dissected clearly shows the layout of the Papez circuit. Due to the location of the structures in the circuit, the resulting shape is a limbus.

The papez circuit2
The Papez Circuit

  • This is what drove MacLean to call the circuit the limbic system when he later modified the circuit.

  • Various studies indicate that the Papez circuit is greatly influenced by the cerebellum and that perhaps the hippocampus is not the starting point of the circuit.

  • Anatomically, this would make sense since the cerebellum is connected to the circuit with many fine fibers and fiber bundles.

  • Chemical lesions on the cerebellum seem to have an inhibitory effect on the circuit. Animal behavioral studies show that electrical stimulation of the anterior cerebellum can cause arousal, predatory attack, and feeding responses, all of which are thought to be expressions of emotion. Overall, these studies provide evidence that the cerebellum may also be included in an emotional system of the brain.

The papez circuit3
The Papez Circuit

The papez circuit4
The Papez Circuit

The papez circuit5
The Papez Circuit

The papez circuit6
The Papez Circuit








Limbic Function

Functional Aspects of Limbic System

1.Emotion - Affective Behavior


Limbic and Prefrontal Cotex

- Desire, Motivation, Goal-directed Behavior

Hypothalamus and Brain Stem

- ANS - maintenance of self (appetites)

maintenance of species (sexual function)

cf. Klüver-Bucy Syndrome

2. Memory and Learning

Papez Circuit

cf. Korsakoff’s syndrome

Limbic Function

Evolution and Limbic System

- Triune Concept of MacLean

Protoreptilian Brain

(R Complex) ---- Instinct

Paleomammalian Brain

--- Limbic System ---- Emotion

Neomammalian Brain

--- Neocortex --- Analytical, Reasoning


Concept of Limbic System

Broca (1877) - ‘La Grand Lobe Limbique’

Papez (1937) - ‘Limbic Circuit’ - emotion

MacLean (1952) - ‘Limbic System’ - visceral brain

Nauta (1972) - ‘Septo-hypothalamo-mesencephalic continuum’

PAUL BROCA (1824-1880)

JAMES PAPEZ (1883-1958)

Limbic System

- term of Paul MacLean (1952)

- Visceral Brain

- triune concept of brain evolution


Nucleus accumbens

amygdaloid nuclear complex

orbitofrontal cortex

Some psychiatric implications on

physiological studies on fronto-

temporal portions of limbic system

(visceral brain). Electroencephalogr

Clin Neurophysiol 4: 407-418, 1952

Paul D. MacLean

Main Components of Limbic System








NAUTA’SSepto-(Preoptico)-Hypothalamo- Mesencephalic Continuum












Limbic System


of Emotion





Components of the Limbic System (I)

Basal Forebrain Area

Substantia Innominata

Basal Nucleus of Meynert

Ventral Pallidum

Nucleus Accumbens (Septi)

Septal Region

Septal Area

Paraterminal Gyrus

Subcallosal Gyrus

Septal Nuclei

Dorsal, Lateral and Medial

Septal Nuclei

Nucleus of Diagonal Band of Broca

Bed Nucleus of Stria Terminalis

Amygdaloid Nuclear Complex

Corticomedial Nuclear Group

Basolateral Nuclear Group

Central Nucleus


Limbic Lobe

Gyrus Fornicatus

Cingulate Gyrus

Parahippocampal Gyrus

Hippocampal Formation


Dentate Gyrus


Hippocampal Rudiments

Fasciolar Gyrus

Indusium Griseum

Olfactory Cortex (Rhinencephalon)

- Piriform Lobe

Prepiriform Cortex

Periamygdaloid Cortex

Entorhinal Cortex

Components of the Limbic System (II)


Thalamus, Limbic

Anterior Nuclear Group

Mediodorsal (MD) Nucleus

Midline Nuclei


Preoptic Region

Preoptic Periventricular Nucleus

Medial Preoptic Nucleus

Supraoptic Region

Suprachiasmatic Nucleus

Anterior Nucleus

Supraoptic Nucleus

Paraventricular Nucleus

Tuberal Region

Dorsomedial Nucleus

Ventromedial Nucleus

Infundibular (Arcuate) Nucleus

Mammillary Region

Lateral, Medial and Intermediate

Mammillary Nucleus

Posterior Nucleus


Habenular Nucleus

Medial Habenular Nucleus

Lateral Habenular Nucleus

Pineal Gland


Limbic Midbrain Area

Median Raphe Nucleus

Dorsal Raphe Nucleus

Ventral Tegmental Area

Dorsal Tegmental Nucleus

Periaqueductal Gray

Limbic Lobe

Classification of Cortex

Isocortex - Neocortex




Dentate Gyrus


Olfactory Bulb

Piriform Lobe

Mesocortex (Juxtallocortex,

Periallocortex, Mesallocortex)

Cingulate Gyrus

Limbic Lobe

Gyrus Fornicatus

Cingulate Gyrus

Parahippocampal Gyrus

Entorhinal Area


Hippocampal Formation

Hippocampus Proper

(Ammon’s horn)

Dentate Gyrus


Hippocampal Rudiments

Fasciolar Gyrus

Indusium Griseum

Hippocampal Formation

Hippocampus Proper

(Ammon’s horn,


Dentate Gyrus



Ammon’s horn

(Cornu Ammonis)

Subdivision of Cornu Ammonis (Hippocampus proper)

- subdivision by Lorente de Nó (1934)




CA4 - Area Dentata

Fascia Dentata

Rafael Lorente de Nó

Hippocampal Formation

Dentate gyrus,CA1, CA2, CA3, CA4,subiculum, enthorinalcortex

Hippocampal Formation

Hippocampus Proper




CA4 - Area Dentata

Dentate Gyrus







Navigation spatial memory
Navigation- spatial memory

  • Place cell circuit tracks position

Septal Region


Septum pellucidum

Septum Verum

- Septal Nuclei


Stria Medullaris Thalami

to medial habenular nucleus

Medial Forebrain Bundle

to hypothalamus and midbrain

Fornix - to hippocampus

Stria Terminalis & Diagonal Band

from amygdaloid complex

Septal Region

Septal Area

Paraterminal (Subcallosal) Gyrus

Subcallosal Area (Parolfactory Area)

Septal Nuclei

Dorsal Septal Nucleus

Lateral septal Nucleus

Medial Septal Nucleus (Ch1)

Nucleus of Diagonal Band

of Broca (Ch2, Ch3)

Bed Nucleus of Stria Terminalis

Bed Nucleus of

Anterior Commissure

Basal Forebrain Area and Limbic Basal Ganglia

Limbic Basal Ganglia

Nucleus Accumbens Septi

(Ventral Striatum)

afferents from

hippocampal formation

amygdaloid body

cingulate gyrus

ventral tegmental area

dorsal raphe nucleus

efferents to ventral pallidum

Ventral Pallidum

efferents to

mediodorsal (MD) thalamus

substantia nigra

subthalamic nucleus

amygdaloid nucleus

lateral habenular nucleus

Basal Forebrain Area

- structures deep to the

anterior perforating substance

Olfactory Tubercle

Substantia Innominata

Basal Nucleus of Meynert (Ch4)

cf. Alzheimer’s disease

Ventral Pallidum

- non cholinergic portions

of the substantia innominata

- part of limbic basal ganglia

Theodor Meynert


  • Austrian Neurologist

  • Professor of Neurology and

  • Psychiatry in Wien University

  • Teacher of Sigmund Freud

  • Use serial sections in histology

  • of nervous system

  • Basal Nucleus of Meynert

  • in substantia innominata

  • Dorsal tegmental decussation

  • of Meynert

Basal Forebrain Area Components


Ventral Striatum, Part of

Ventral Pallidum

Basal Nucleus of Meynert (Ch4)

Extended Amygdala

cf. Cholinergic Cell Groups (Mesulam)

(Magnocellular Basomedial Telencephalic Complex )

1. Ch1 (Medial Septal Nucleus)

2. Ch2 (Nucleus of Diagonal Band of Broca)

3. Ch3 (Nucleus of Diagonal Band of Broca)

4. Ch4 (Basal Nucleus of Meynert)

5. Ch5 (Pedunculopontine Tegmental Nucleus)

Amygdala Components

L. almond

K. F. Burdach’s


Extended Amygdala Components

Extended Amygdala

Central Amygdaloid Nucleus

Medial Amygdaloid Nucleus

Bed Nucleus of

Stria Terminalis (BST)

- bridging cell groups directly

interconnects amygdaloid

and bed nucleus of stria

terminalis (BST)

which refered to as

Extended amygdala.


Afferents from

Intra-amygdaloid association

fibers from basolateral

amygdaloid nucleus,

whic recieves wealth of

modality-specific and

multimodal sensory input

from the cerebral cortex.

Efferents to

Hypothalamus and

Brain Stem

Amygdaloid Nuclear Complex Extended Amygdala

A. bed nucleus of


B. centromedialamygdala

C. basolateralamygdala

D. cortical amygdala

E. connections between

extended amygdala

and amygdala:

sublenticular portion of


1. striaterminalis

pleasure Extended Amygdala

Medial forebrain bundle

- Ventral tegmental area

Limbic Thalamus Extended Amygdala

Thalamus, Limbic

Anterior Nuclear Group

Anteroventral Nucleus (AV)

Anterodorsal Nucleus (AD)

Anteromedial Nucleus (AM)

Lateral Dorsal (LD) Nucleus

Mediodorsal (MD) Nucleus

Pars magnocellularis (MDmc)

Pars parvocellularis (MDpc)

Pars paralaminaris (MDpl)

Pars densocellularis (MDdc)

Midline Nuclei

Paratenial Nucleus (Pt)

Reunience Nucleus (MV)

Submedial Nucleus (Sm)

Rhomboid Nucleus (Rh)


Anterior Nuclear Group

from mammillary body,

hippocampal formation,

cingulate gyrus

to cingulate gyrus



from primary olfactory cortex,

ventral pallidum

to orbitofrontal cortex

MDpc, MDpl, MDdc

from substantia nigra

limbic midbrain area

to medial frontal cortex

frontal eye field (area 8)

Connections of the Limbic Thalamus Extended Amygdala






Eye Field









Hypothalamus Extended Amygdala

Functional Aspects of Hypothalamus

1. Endocrine Function

Hormones of the Neurohypophysis - ADH, Oxytocin

(Supraoptic and Paraventricular Nucleus)

Releasing and Inhibiting Hormones (Tuberal region)

- Hypothalamo-hypophyseal Portal System

2. Visceral Function (Autonomic Center of CNS)

3. Limbic Function

Hypothalamic Cell Group Extended Amygdala

Silent Attack Extended Amygdala

- little emotional


- evoked by electric

stimulation of

perifornical nuc.

of hypothalamus

“The cat moves swiftly

and with little sign of

emotion to bite the

rat’s neck and kill it”

(Siegel & Brutus, 1990)

Sham Rage Extended Amygdala

- an affective attack


- evoked by radio

stimulation of

medial hypothalamus

“Because the cat does not

direct its attack toward any

target, we regard this as

just a fragment of a normal

attack” (Delgado, 1981)

Anorexia Extended Amygdala


Karen Anne Carpenter


Olfactory Extended Amygdala







Septo-(Preoptico)-Hypothalamo- Mesencephalic Continuum












Limbic System

Papez Circuit Extended Amygdala

Entorhinal Cortex

(Area 28)

alveolar path

perforant path












Thalamic Nuclei

mammillothalamic tract

Papez Circuit Extended Amygdala

A. Hippocampal Formation

B. mammillary body

C. thalamic anterior nucleus

D. cingulate gyrus

1. fornix

2. mammillothalamic tract

3. thalamocortical radiation

4. cingulum

Heinrich Klüver Paul Clancy Bucy Extended Amygdala

(1897-1979) (1904-1992)

Limbic Function Extended Amygdala

Klüver-Bucy syndrome

 Monkey or cats with bilateral damage of temporal lobes

including amygdala and hippocampal formation

Fail to display normal fear of anxiety (docility)

- attempt to pick up snakes and lighted matches

Regression to oral stage

- put almost anything into mouth

Marked increase in both the amount and diversity of

sexual activity