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Amygdala and Hippocampus and Hypothalamus
Maryann Martone, Ph. D.
NEU257
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
From the Digital Anatomist website
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
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
Olfactory Cortex
http://www.hallym.ac.kr/~de1610/nana/chp-12n.htm#II
Olfactory Cortex
Monkey brainFrom the Digital Anatomist website
Rodent Brain
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
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.
Human (from digital anatomist)
Macaque (from brainmaps.org)
Mouse
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”
http://www.driesen.com/amygdala_connections.htm
Price, Ann. NY Acad Sci., 985:50-58 (2003)
•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
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
“C” shaped structure in medial temporal lobe
http://www.hallym.ac.kr/~de1610/nana/chp-12n.htm#IIFrom Digital Anatomist
Development
http://www.hallym.ac.kr/~de1610/nana/chp-12n.htm#II
From Digital Anatomist
From Digital Anatomist
Gross Anatomy
•Septal-temporal poles
•Fornix
•Fimbria, body, columns
Rodent
Human
Supracommissural hippocampus=supracallosal gyrus, indusium griseum
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)
Cytoarchitecture
Human
Rodent
•Two interlocking cell fields
•Dentate gyrus
•hippocampus
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
Intrinsic connectionsCajal, 1901
http://www.angelfire.com/yt/yas709neuroscience/hippocampus.htm
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
Anatomy of Hypothalamus
science.tjc.edu/ images/brain/Index.htm
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
Cytoarchitecture
Macaque: brainmaps.org
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
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
“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
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
Magnocellular Secretory System
clem.mscd.edu/~raoa/ bio2320/endo1/sld003.htm
• “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
Hypothalamic Portal System
clem.mscd.edu/~raoa/ bio2320/endo1/sld003.htm
Peripheral Influence of Hypothalamus
clem.mscd.edu/~raoa/ bio2320/endo1/sld003.htm
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