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Olfactory system, Amygdala and
Hippocampus
Maryann Martone, Ph. D.
NEU257
The Limbic System
“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
•Broca, Papez, Kluver and
Bucy
•Parts of the brain
underlying emotional
behavior
http://www.hallym.ac.kr/~de1610/nana/chp-12n.htm#II
•Associated with the
olfactory system;
rhinencephalon = “smell
brain”
Limbic Structures
• Hippocampus
• Amygdala
• Olfactory system
Terminology
assistance:
http://www.umanitoba.ca/faculties/medi
cine/anatomy/neuro/gloss/gloss.htm
http://braininfo.rprc.washington.edu/ma
inmenu.html
From the Digital Anatomist website
From the Digital Anatomist website
Olfactory System
thalamus.wustl.edu/ course/lim5.gif
From the Digital Anatomist website
Olfactory Cortex
•Also cortical
amygdaloid nucleus
and periamygdaloid
area
•Projects to ventral
striatum, MD
thalamus, insula and
orbitofrontal cortex
•Pyriform cortex = 1˚ olfactory cortex
•Allocortex, paleocortex
•3 layered
From the Digital Anatomist website
Olfactory Cortex
http://www.hallym.ac.kr/~de1610/nana/chp-12n.htm#II
Olfactory Cortex
Monkey brain
From the Digital Anatomist website
Rodent Brain
Amygdala most closely associated with
emotional behavior
•
•
•
•
•
•
“Angst and the Amygdala
“Fear, faces, and the human amygdala.”
“The neurobiology of psychopathy”
“Emotion, decision making, and the amygdala”
“Neuroanatomy of autism”
“The functional neuroanatomy of PTSD: a critical
review”
• “Neurobiology of escalated aggression and
violence.”
– Pub Med search for “Amygdala”
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.
Amygdala
Amygdaloid
complex
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”
Major afferents to the amygdaloid complex
Figure 23-18 Major inputs to the basolateral (blue), central (red), and medial (green) nuclei of the amygdala (Am). Only inputs from
visual association cortex to the basolateral nuclei are shown, although there are similar projections from most or all unimodal sensory
areas. The inputs from limbic cortex to the basolateral nuclei also include a major projection from the insula, which is not present in this
view. B, brainstem (periaqueductal gray, parabrachial nuclei, other nuclei); Hy, hypothalamus; S, septal nuclei; T, thalamus (multiple
nuclei). (Modified from Warwick R, Williams PL: Gray's anatomy, Br ed 35, Philadelphia, 1973, WB Saunders.)
From Nolte
Downloaded from: StudentConsult (on 1 March 2011 06:45 AM)
© 2005 Elsevier
Major efferents to the amygdaloid complex
Figure 23-21 Major outputs from the basolateral (blue), central (red), and medial (green) nuclei of the amygdala (Am). These take three routes: (1) the
stria terminalis, which reaches the septal nuclei (S) and hypothalamus (Hy); (2) the ventral amygdalofugal pathway (see Fig. 23-20B and C) to the
hypothalamus (Hy), thalamus (T; mainly the dorsomedial nucleus), widespread areas of ventromedial prefrontal and insular cortex, ventral striatum
(VS), olfactory structures, and various brainstem sites (B); and (3) direct projections to the hippocampus (HC) and temporal and other neocortical
areas. Only visual cortical areas are shown, although there are similar projections to most or all primary and unimodal sensory areas. (Modified from
Warwick R, Williams PL: Gray's anatomy, Br ed 35, Philadelphia, 1973, WB Saunders.)
From Nolte
Downloaded from: StudentConsult (on 1 March 2011 06:45 AM)
© 2005 Elsevier
Connections of the central medial group
cal.vet.upenn.edu/neuro/server/ slides/ns_075-BNST.jpg
•Extended amygdala: Central medial group shares continuity and similarity
with parts of substantia innominata and bed nucleus of the stria terminalis
Summary of Forebrain Systems
• Cortical vs subcortical
– According to Swanson, the forebrain can be
understood in terms of two systems:
– Cortex and cortical (basal) nuclei
• Cortex: glutamate projection neurons
» Projections to striatum
» Interconnections with thalamus
• Striatal: GABA projection neurons
• Pallidal: GABA ---> Thalamus --> Cortex
The Hippocampus
• Greek: “Sea Monster”
• Another terminology tangle
– 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
From Digital Anatomist
http://www.hallym.ac.kr/~de1610/nana/chp-12n.htm#II
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
Supracommissural
hippocampus=supracallosal
gyrus, indusium griseum
Human
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
•Two interlocking cell
fields
•Dentate gyrus
•hippocampus
Human
Rodent
so sp
•Stratum oriens
•Stratum pyramidale
•Stratum lucidum
•Stratum radiatum
•Stratum lacunosummoleculare
sl
sr
sl-m
ml
•ml=molecular layer
Hilus
www.deltagen.com/.../nervous/ cerebrum_hippo_10x.htm
CA1-CA3: pyramidal neurons
Dentate Gyrus: granule cells
Cajal, 1901
Intrinsic connections
fornix
http://www.angelfire.com/yt/yas709neuroscience/hippocampus.htm