Sjldllds ;l;sf’;’;s بسم الله الرحمن الرحیم 1390 1 Medical Science University...

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بسم الله الرحمن الرحیم

1390 1Medical Science University of Isfahan, Anatomical Sciences

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1390 Medical Science University of Isfahan, Anatomical Sciences

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2Figure 12.2b

عّن�ین من فهو والّنجوم التشریح یعلم لمالله معرفت فی

• One who do not have the knowledge of Anatomy and Astronomy, will not be able to know God

علم که کسینجوم و تشریح

از نداند راخدا شّناخت

ست ا ناتوان

علم که کسینجوم و تشریح

از نداند راخدا شّناخت

ست ا ناتوانآفتابیش بشکافی که را ذره هر دل

بیّنی میان در

The Limbic System

•Broca, Papez, Kluver and Bucy

•Parts of the brain underlying emotional behavior

•Associated with the olfactory system; rhinencephalon = “smell brain”

“The hypothalamus, the anterior thalamic nucleus, the cingulate gyrus, the hippocampus and their interconnections, constitute a harmonious mechanism which may elaborate the functions of central emotion as well as participate in

the emotional expression.” -James Papez, 1939

http://www.hallym.ac.kr/~de1610/nana/chp-12n.htm#II

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Olfactory System

From the Digital Anatomist website

thalamus.wustl.edu/ course/lim5.gif

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Olfactory Cortex

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•Extended amygdala: Central medial group shares continuity and similarity with parts of substantia innominata and bed nucleus of the stria terminalis

Connections of the central medial group

cal.vet.upenn.edu/neuro/server/ slides/ns_075-BNST.jpg

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“C” shaped structure in medial temporal lobe

http://www.hallym.ac.kr/~de1610/nana/chp-12n.htm#IIFrom Digital Anatomist

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Development

From Digital Anatomist

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Gross Anatomy

•Septal-temporal poles

•Fornix

•Fimbria, body, columns

Rodent

Supracommissural hippocampus=supracallosal gyrus, indusium griseum

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Connections•Afferents:

•Much of cortex is reciprocally connected to entorhinal cortex•Cholinergic and GABA input via septal nuclei•Amygdala•VTA, LC, Raphe

•Efferents•Via the fornix•Precommissural: septal nuclei•Post-commisural: mammillary bodies (to anterior thalamic nucleus via mammillothalamic tract)

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THANK YOU

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16Figure 12.2b

Limbic System 18th Lecture

Limbic lobeHippocampal formatiomHipocampus

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Mesencephalon Diencephalon

Telencephalon

Limbic System

IncludesStructures of

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Limbic System

• Libmbic lobe– Hippocampal formation– Septal area– Parahippocampal gyrus– Cingulate gyrus– Insula

• Related subcortical nuclei :– Amygdala– Some part of Mesencephalone– Some part of Diencephalone

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Limbic System

Limbic Lobe (Cortex) Related Subcortical Nuclei

Hippocampal formation Amygdala

Septal Area

Parahippocampal gyrus

Cingulate gyrus

Insula

Some parts of Diencephalon

Some nuclei of Midbrain

Corticomedial group

Bsolateral group

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Limbus = A ring

• A ring of cortex around Corpus Callosum and Diencephalon

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Hippocampal formation

Hippocampus Dentate Subiculum

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LIMBIC SYSTEM

(from http://ferguson.bvu.edu/BioPsych/Chpt4_Neuroanatomy.html)

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Limbic functions

Regulate Emotional & Motivational

aspect of Behaviour

Changing short-termMemory into long-term

Memory (Learning)

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Embryology of Limbic System

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Embryology of Limbic System

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Hippocampal formation:

• 1- Hippocampus, (efferent cortex)

• 2- Dentate gyrus (afferent cortex)

• 3- Subiculum (efferent cortex)

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Cornu Ammonis

• Hippocampus = Ammon,s horn (Cornu) after Egyptian deity with ram,s head

• For research purpose, it is divided into 4 cornu ammonis (CA) zones :– CA1– CA2– CA3– CA4

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Anatomy of Hippocampus,

• The hippocampus is a scrolled structure located in the medial temporal lobe. In a coronal section, it looks like a hippocampus

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Anatomy of Hippocampus

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Parts of Hippocampus

• The hippocampus can be divided into 4 different areas,

• Areas CA3 and CA1 are more diffuse; the small CA2 is hard to distinguish between them.

• The dentate gyrus is the dense dark layer of cells at the "tip" of the hippocampus.

• The subiculum sits at the base of the hippocampus, and is continuous with entorhinal cortex, which is part of the parahippocampal gyrus.

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Limbic Function

• Regulate :

• Emotional and motivational aspects of behavior

• Limbic projection to forebrain contribute to emotions and provide motivation for behaviors essential to survival

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Function of limbic System

• A- Limbic system is able to influence many aspects of emotional behavior via hypothalamus, which in turn employs :– 1 Autonomic nervous system– 2 Endocrine system

• B- Converting short term memory to long term memory and facilitate learning

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Connections of hippocampus

• 1- Perforant pathway from entorhinal area to dentate gyrus

• 2- Axons from dentate to pyramidal cell in CA3 sector

• 3- Axons from CA3 to fimbria

• 4- A branch from the CA3 fiber called Schaffer collateral, projects to CA1

• 5- CA1 projects to entorhinal cortex

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Afferent Connections to Hippocampus

• 10 Groups of fibers pass to Hippocampus:

• 1- Fibers from cingulate gyrus

• 2- Fibers from septal area

• 3- Fibers from opposite hippocampus

• 4- Fibers from indusium grisum

• 5- Fibers from enthorhinal or olfactory area

• 6- Fibers from dentate and subiculum

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Afferents connections cont…

• 6- From auditory, visual, olfactory association cortex

• 7- Cholinergic fibers from septal area

• 8- Noradrenergic fibers from ceruleus nucleus

• 9- Cerotonergic fibers from raphe nuclei

• 10- Dopaminergic fibers from ventral tegmental area

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Efferents from hippocampus

• 1- Massive effertent fibers to association areas of cortex

• 2- Fornix fibers to :• Septal area• Anterior hypothalamus• Mammillary body, anterior thalamus and cingulate

cortex from which returns to hippocamus• Medial forbrain bundle (MFB)

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Medial forebrain bundle

• Is a complex group of fibers arising from basal olfactory regions, the septal nuclei, the periamygdaloid region and subiculum that passes to and through, the lateral preoptic and lateral hypothalamic regions. The bundle is formed at the level rostral to the anterior commissure, mainly of fibers from septal regions.

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Efferent Connections of Hippocampus

• Axons of large pyramidal cells of hippocampus emerge to form alveus and fimbria and fornix which pass to :

• 1- Mammillary body• 2- Anterior nucleus of thalamus• 3- Tegmentum of midbrain• 4- Septal area and anterior hypothalamus• 5- Habenular nuclei through stria

medullaris thalami

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Papez circuit

• 1- Backward projection neurons in cingu.

G.• 2- Projection into

entorhinal gyrus• 3- Projection into hipp.• 4- Fornix• 5- Mammillothalamic t• 6- Projection from ant.

thalamic to cingulate

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Memory

• Autopsy and imaging studies of patients with memory disorders suggest that:

• 1- Hippocampus and related structures, such dorsomedial nucleus of thalamus are important in memory processing.

• 2- Bilateral damage to these structures results in impairment of recent memory

• 3- Lesion of hippocampus results in individual being unable to store long term memory

• 4- Hippocampus is concerned in converting short term memory to long term memory

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Memory Deficit

• A stroke can have this effect, but there must be bilateral damage of the hippocampal to affect memory. Therefore only situations that deplete blood or oxygen flow to the entire brain will produce a memory deficit. The pathology of severe temporal lobe epilepsy looks very similar to ischemic damage.

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MEMORY

• If the amygdala is FEAR, then the hippocampus is MEMORY. To understand exactly how the hippocampus is involved in memory, however, you must first know a little about memory.

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Memory

Short term)recent,(

recalling 7 digit

numbers after a few seconds

Long term,recallingpreviously

learned knowledge

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Dissociative or

psychogenicRetrograde

Anterograde

Amnesia

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Diseases of the hippocampus:

• The hippocampus is particularly vulnerable to several disease processes, including ischemia, which is any obstruction of blood flow or oxygen deprivation, Alzheimer's disease, and epilepsy. These diseases selectively attack CA1, which effectively cuts through the hippocampal circuit.

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• Progressive dementia

• Forgetful, abnormalities of memory, cognition, orientation and behavior

• Neuronal loss in hippocampus/ parahippocampal gyrus/cortex

• Reduction in cholinergic innervation of cortex

Alzheimer’s Disease

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34533_wallpaper400.jpg34533_wallpaper400.jpg

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The amygdala

• If you remember only one word about the amygdala, the word is Fear. And then are:

• Fight or Flight

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Inputs to Amygdala

• The association areas of visual, auditory, and somatosensory cortices are the main inputs to the amygdala

• It must to recognize the elements of a scene that signal danger.

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Outputs from Amygdala

• ِِ00 Amygdala must be able to control the autonomic system, to provoke such an instant sympathetic response. The main outputs of the amygdala are to the hypothalamus and brainstem autonomic centers, including the vagal nuclei and the sympathetic neurons.

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Amygdala

• The amygdala is also involved with mood and the conscious emotional response to an event, whether positive or negative. To this end, the amygdala is also extensively interconnected with frontal cortex, mediodorsal thalamus, and the medial striatum.

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Clinical Points:

• Kluver-Bucy syndrome following bilateral removal of temporal lobe:

• 1- Loss of fear and anger

• 2- Vision agnosia

• 3- Increased appetite

• 4- Increased sexual activity

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Limbic functions

Regulate Emotional & Motivational

aspect of Behavior

Changing short-termMemory into long-term

Memory (Learning)

Feeling Feeding Fighting FleeingSexual Activity

Ablation of amygdala suppresses fighting but increases feeding and sexual activity

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Reticular formation

• Phylogenetically a very old neural network

• Made of nerve fibers and nerve cells

• Extend through axis of CNS from spinal cord to cerebrum

• Is strategically placed among nerve tracts and nuclei with vital importance, that is brain stem

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Neurons of Reticular formation

• Isodendritic neurons:– Long branching axon– Branching dendrites in a plane vertical to

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Function of Reticular formation

• It receives input from all sensory systems

• It gives output to all motor systems

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General arrangement of reticular formation

• Reticular formation refers only to polysynaptic network in brain stem although extends cranially and caudally to whole CNS:- Median column, intermediate or raphe nucleus- Medial column, magnocelluar neurons

(efferent)- Lateral column, parvicellular neurons,

(afferent)

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Functions of reticular formationIt controls:

• Skeletal and viscera muscle activity, walking, talking, chewing, laughing, vomiting

• Somatic and visceral sensations, gating mechanism

• Autonomic and endocrine system• Level of consciousness, reticular activating

system• Biological clock

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Components of reticular formation

• Pattern generators:– Somatic and visceral motor centers– Oscilators

• Monaminergic group cells which give rise to:– Raphespinal pathway, Serotonergic pathway– Ceruleospinal pathway, noradrenergic pathway

Reticular Reticular FormationFormation

A. Raphe NucleiA. Raphe Nuclei B. Central B. Central Nuclear GroupNuclear Group

C. LateralC. Lateral Nuclear GroupNuclear Group

D. PrecerebellarD. Precerebellar Reticular NucleiReticular Nuclei

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THE ENDTHE END

Sjldllds ;l;sf’;’;s بسم الله الرحمن الرحیم 1390 1 Medical Science University...

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