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Amygdala and Hippocampus and Hypothalamus Maryann Martone, Ph. D. NEU257

Limbic System lecture, 2008

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Page 1: Limbic System lecture, 2008

Amygdala and Hippocampus and Hypothalamus

Maryann Martone, Ph. D.

NEU257

Page 2: Limbic System lecture, 2008

The Limbic System

•Broca, Papez, Kluver and Bucy, McClean

•Parts of the brain underlying emotional behavior

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

•“Often, the term “limbic” structure is used in a vague fashion to distinguish it from motor structures…” Heimer, 1996

“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

Limbic Lobe: Broca

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From the Digital Anatomist website

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Olfactory System

From the Digital Anatomist website

thalamus.wustl.edu/ course/lim5.gif

http://da-atlases.biostr.washington.edu:80/cgi-bin/DA/PageMaster?atlas:NeuroSyllabus+ffpathIndex/Syllabus^Chapters/VisceralAfferent/OlfSystem+2

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Olfactory Cortex

•Pyriform cortex = 1˚ olfactory cortex

•Allocortex, paleocortex

•3 layeredhttp://da-atlases.biostr.washington.edu:80/cgi-bin/DA/PageMaster?atlas:NeuroSyllabus+ffpathIndex/Syllabus^Chapters/VisceralAfferent/OlfRegions+2

•Also cortical amygdaloid nucleus and periamygdaloid area

•Projects to ventral striatum, MD thalamus, insula and orbitofrontal cortex

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Olfactory Cortex

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

Page 7: Limbic System lecture, 2008
Page 8: Limbic System lecture, 2008

Olfactory Cortex

Monkey brainFrom the Digital Anatomist website

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Rodent Brain

Page 10: Limbic System lecture, 2008

The Amygdala

• Burdach 1819: the amygdaloid complex (“almond”)

• Johnston 1923: central, medial, cortical, basal nuclei

• Price 1980’s: basolateral, cortical, central medial nucleus

• De Olmos and Heimer 1991: extended amygdala• Swanson 1998: there is no amygdala

Page 11: Limbic System lecture, 2008

The amygdaloid complex• Over 20 divisions/nuclei, depending on whom you talk to• 500-1000 different connections identified (Swanson)

• Swanson: “The amygdala is neither a structural nor a functional unit of the cerebral hemispheres; instead, its cell groups participate in at least four distinct, though interconnected, functional systems or differentiations of the corticostriatopallidal system…. Terms such as 'amygdala' and 'lenticular nucleus' combine cell groups arbitrarily rather than according to the structural and functional units to which they now seem to belong..”

» L. W. Swanson: The amygdala and its place in the cerebral hemisphere, PNAS 985: 174, 2003.

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Human (from digital anatomist)

Macaque (from brainmaps.org)

Mouse

Page 13: Limbic System lecture, 2008

One view(based on Heimer, 1996)

• Basolateral– Similar to cortex– Projects to ventral striatum– Has pyramidal like cells– Receives input from primary sensory cortex, polysensory cortex and thalamus– Connections are reciprocal

• Cortical– Olfactory amygdala– Receives direct input form olfactory system, both the olfactory bulb and olfactory cortex

• Central Medial group– Main output of amygdaloid complex– Input from hippocampus, orbitofrontal, insula, anterior cingulate cortex as well as

basolateral group– Projects to hypothalamus, brainstem via stria terminalis and amygdaloventral fugal

pathway– Part of “central autonomic network”

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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

Page 16: Limbic System lecture, 2008

The Hippocampus

• Greek: “Sea Monster”• Another terminology mess

– Allocortex/ archicortex– Hippocampal formation (after Amaral and Witter)

• Dentate gyrus• Hippocampus proper “Cornu ammonis”• Subicular complex

– Subiculum– Presubiculum– parasubiculum

• Entorhinal cortex

Page 17: Limbic System lecture, 2008

“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

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

From Digital Anatomist

From Digital Anatomist

Page 19: Limbic System lecture, 2008

Gross Anatomy

•Septal-temporal poles

•Fornix

•Fimbria, body, columns

Rodent

Human

Supracommissural hippocampus=supracallosal gyrus, indusium griseum

Page 20: Limbic System lecture, 2008

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)

Page 21: Limbic System lecture, 2008
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Cytoarchitecture

Human

Rodent

•Two interlocking cell fields

•Dentate gyrus

•hippocampus

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Hilus

CA1-CA3: pyramidal neurons

Dentate Gyrus: granule cells

www.deltagen.com/.../nervous/ cerebrum_hippo_10x.htm

sospsl

sr

ml

sl-m

•Stratum oriens•Stratum pyramidale•Stratum lucidum•Stratum radiatum•Stratum lacunosum-moleculare

•ml=molecular layer

Page 24: Limbic System lecture, 2008

Intrinsic connectionsCajal, 1901

http://www.angelfire.com/yt/yas709neuroscience/hippocampus.htm

Page 25: Limbic System lecture, 2008

Hypothalamus: General description

• Master regulator!!• Vital regulatory functions include: temperature, heart rate, blood

pressure, blood osmolarity, goal seeking behavior, emotional behavior, visceral nervous system, sexual activity, food & water intake

• homeostasis

• Below rostral thalamus (hypo =“under”/”beneath)• Forms floor and lower walls of third ventricle• Contains various classes of peptidergic neuroendocrine cells

which control endocrine function• Communicates with cortex via limbic system and also via direct

projections

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Anatomy of Hypothalamus

science.tjc.edu/ images/brain/Index.htm

Page 27: Limbic System lecture, 2008

Anterior (supraoptic): preoptic, superchiasmatic, supraoptic, paraventricular

Middle (tuberal): dorsomedial, ventral medial nuclei, arcuate nucleus

Posterior (mammillary): mamllary body, posterior hypothalamic area, tubermammillary nucleus

Medial-Lateral Zones

Periventricular

Medial

Lateral

Page 28: Limbic System lecture, 2008

Cytoarchitecture

Macaque: brainmaps.org

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Main Inputs to Hypothalamus

• receives info on external and internal conditions: – specific sensory info (e.g., direct retinal projection

to suprachiastmatic nucleus)– input from visceral senses (NTS: nucleus of the

solitary tract-taste)– contains many neurons that are sensitive to local

temperature, osmolarity, glucose, sodium– circulating hormones influence it via the

circumventricular organs• Brain regions near ventricles that lack a blood-brain

barrier, e.g., subfornical organ, OVLT, median eminence

Page 30: Limbic System lecture, 2008

Hypothalamus pathways

Afferent Pathway Projecting from

Median forebrain bundle Collaterals from other tracts

Fornix Hippocampus (to MB)

Stria terminalis amygdala

Efferent Pathway Projecting to

hypothalamicohypophyseal (from supraoptic nuclei)

Neurohypophysis (pituitary)

Mammillothalamic tract Anterior thalamic nucleus

Widespread projections to many brain regions, including the cerebral cortex, via histamine and hypocretin containing neurons in the tuberal region of the hypothalamus

Page 31: Limbic System lecture, 2008

“The medial forebrain bundle is one of the most famous hypothalamic fiber bundles, but also one of the most

incomprehensible”-Lennart Heimer

• Axons from olfactory related areas

• Monoaminergic axons• Ascending and

descending fibers similar to those found in the brain stem reticular formation

• Collaterals of other pathways

• Amygdalar fibersFrom braininfo.org

Page 32: Limbic System lecture, 2008

Peptidergic neuroendocrine cells: Magnocellular neurons

• “Large” neurons• Located in paraventricular and supraoptic

nuclei• Secrete oxytocin and vasopressin into

general circulation via posterior pituitary• Oxytocin uterine contraction & milk

ejection• Vasopressin vasoconstriction, water

resorption by the kidney

Page 33: Limbic System lecture, 2008

Magnocellular Secretory System

clem.mscd.edu/~raoa/ bio2320/endo1/sld003.htm

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• “small” neurons• Located in medial basal region, arcuate and tuberal

nuclei, periventricular region, preoptic and paraventricular nuclei

• Secrete releasing and inhibiting hormones into portal vasculature via anterior pituitary

• Nobel prize awarded to Guillemin (Salk), Schally and Yalow in 1977 for their (independent) work in proving the hypothesis that the hypothalamus releases hormones that regulate the pituitary

Peptidergic neuroendocrine cells: Parvocellular neurons

Page 35: Limbic System lecture, 2008

Hypothalamic Portal System

clem.mscd.edu/~raoa/ bio2320/endo1/sld003.htm

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Peripheral Influence of Hypothalamus

clem.mscd.edu/~raoa/ bio2320/endo1/sld003.htm

Page 37: Limbic System lecture, 2008

Hypocretin

From Thannickal et al., Neuron 27: 469, 2000

•Also known as “orexin”

•Peptide involved in arousal and feeding behavior

•Project to thalamus, cortex and brainstem regions associated with arousal, cardiovascular control, and autonomic functions

•Few thousand neurons

•Loss of hypocretin neurons implicated in human narcolepsy