5. Paul D. MacLean (1913- )
Limbic System
- term of Paul MacLean (1952)
- Visceral Brain
Hypothalamus
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
6. Septo-(Preoptico)-Hypothalamo- Mesencephalic Continuum
Main Components of Limbic System
Septal
Region
Hypothalamus
Limbic
Midbrain
Area
Hippocampal
Formation
Limbic cortex
Amygdaloid
Nuclear
Complex
Spinal
Cord
&
Brain
Stem
Limbic System
7. īĄ Scoville and Milner ī memory loss
following bilateral ATL
ī§ Bilateral hippocampal ablation ī loss of recent
memory and anterograde amnesia
īĄ The amygdala ī German physician Burdach
in the early 19th century.
9. ī KlÃŧver and Bucy in 1939 ī hypersexuality
in monkeys after bilateral temporal lobectomy
ī The human counterpart was described by
Terzian and Dalle Ore in 1955 and by
Marlowe in 1975.
10. ī structures that form a limbus (ring or border) around the brain
stem.
ī The limbic lobe is a synthetic lobe whose component parts are
derived from different lobes of the brain (frontal, parietal,
temporal)
ī subcallosal gyrus
ī cingulate gyrus
ī isthmus
ī parahippocampal gyrus
ī uncus
The term limbic system refers to the limbic lobe and the
structures connected to it.
11. īĄ crescent of tissue
that caps the lateral
end of the fissure,
bulges into the
medial wall and
floor of the
temporal horn and
then curves
medially above the
dentate gyrus
14. īĄ Originally, the limbic lobe was assigned a
purely olfactory function.
ī§ only a minor part of the limbic lobe has
olfactory function
īĄ Rest of the limbic lobe plays a role in
emotional behavior and memory
15. ī limbic lobe and all the cortical and subcortical
structures related to it
ī Septal nuclei
ī Amygdala
ī Hypothalamus (particularly the mamillary body)
ī Thalamus (anterior and medial thalamic nuclei)
ī Brain stem reticular formation
ī Epithalamus
ī Neocortical areas in the basal fronto-temporal region
ī Olfactory cortex
ī Ventral parts of the striatum
16.
17. īĄ Reticular Formation of the Brain Stem and Spinal
Cord
ī§ limbic nuclear groupings
(1) mesencephalic reticular formation ī hypothalamus,
thalamus, and septum
(2) the locus ceruleus of the upper pons and the raphe of
the midbrain ī ascending serotoninergic and
adrenergic systems onto the diencephalon and
telencephalon.
18. Interpeduncular Nucleus
īĄ habenulopeduncular tractī hypothalamus
and the midbrain limbic region
īĄ Amygdaloidal information ī via the stria
terminalis to the septum and then from the
septum to the interpeduncular nucleus.
19. Hypothalamus
īĄ highest subcortical center
ī§ body temperature
ī§ Appetite
ī§ water balance
ī§ pituitary functions
ī§ emotional content
īĄ most potent ī control of the autonomic
nervous system
21. âĸ Septal area
âĒ septum pellucidum ī glia ,lined by ependyma
âĒ septum verumī vental to s. pellucidum
âĒ Poorly developed in humans
22. ī The hippocampal-septal relationship is
topographically organized
ī specific areas of the hippocampus project on
specific regions of the septum
ī CA1 ī medial septal region
ī CA3 and CA4 ī lateral septal region
ī medial septal region to CA3 and CA4
25. īĄ ACTIVITY
ī§ high initial state of activity in response to a novel
situation which rapidly declines almost to
immobility.
īĄ LEARNING
ī§ tend to learn tasks quickly and perform them
effectively once they have been learned.
īĄ REWARD
ī§ Stimulation ī pleasure or rewarding effects.
26. īĄ AUTONOMIC EFFECTS
ī§ Stimulation ī inhibitory effect
īĄ Cardiac deceleration ī reversible with
atropine
ī§ septal effects are mediated via the cholinergic
fibers of the vagus nerve.
27. īĄ Destruction of the septal nuclei ī behavioral
overreaction to most environmental stimuli.
ī§ changes occur in sexual and reproductive behavior,
feeding, drinking, and the rage reaction
īĄ ACh ī euphoria and sexual orgasm
īĄ Septal recording during sexual intercourse ī spike and
wave activity
īĄ septal damage ī increased sexual activity in humans.
28. īĄ below the caudate
ī§ amygdala ī ventral amygdalofugal pathway
ī§ basal ganglia ī major link between the limbic and
basal nuclei
īĄ high content of acetylcholine
īĄ Alzheimerâs disease ī significant loss of cholinergic
neurons in this nucleus.
29. īą crescent of tissue that caps the lateral end of
the fissure, bulges into the medial wall and
floor of the temporal horn and then curves
medially above the dentate gyrus
35. The Hippocampus
CA fields
A) Lateral Ventricle, B) ependymal glia (ventricular surface), C) Alvear Layer, (pyramidal axons)
3 layers of hippocampus (archicortex):
1. Polymorph Layer (pyramidal axons & basket cells (-))
2. Hippocampal pyramidal layer (pyramidal cell bodies)
3. Molecular Layer (pyramidal dendrites)
A) Lateral ventricle
B) Ependymal glia
C) Alvear layer
1. Polymorph Layer
2. Pyramidal Layer
3. Molecular Layer(pyramidal dendrite)
(pyramidal axon)
(pyramidal cell body)
36. Hippocampus is divided in three parts
Based on relation to brain stem
Head : anterior edge of brain stem
Body : adjacent to brain stem
Tail : ascending , curving behind brain stem
37. Hippocampal Head
The hippocampal head is the voluminous anteror part of the
arc of the hippocapus.
It includes an intraventricular part and an extraventricular
part.
41. Afferent Connections
From Entorhinal Cortex
Alveolar Path
from medial part of EC
to CA1 and Subiculum
Perforant Path
from lateral part of EC
to CA1, CA2, CA3 and
Dentate Gyrus
43. Afferent Connections
EC & Hippocampal Afferents
Surrounding Neocortex
from association areas
- temporal, frontal lobe
Limbic System
from hypothalamus,
amygdala, septal area,
anterior thalamic nuclei,
and midbrain limbic area
45. Efferent Connections
Fornix
- from pyramidal neurons of hippocampus &
subiculum
Postcommissural Fornix â main bundle
to Mammillary Body
Anterior Thalamus
Lateral Septal Nuclei
Hypothalamus
Midbrain Tegmentum
46. Hippocampal Formation:
Circuitry.
A.Components and structure â
a banana-shaped structure with its
components (dentate, hipp,
subiculum) folded upon one
another like a âjelly rollâ.
Inputs are from entorhinal
cortex, which collects info
from other association areas
ī dentate gyrus
ī hipp formation + subculum
ī output to fornix and
also back to entorhinal cortex
47. Summary of Hippocampal Connections
īĄ Entorhinal Cortex
Alveolar Path
from medial part of EC to CA1 and Subiculum
Perforant Path
from lateral part of EC
to CA1, CA2, CA3 and
Dentate Gyrus
īĄ Dentate Gyrus
Mossy fiber - CA3
Schaefer fiber (CA3-CA1)
īĄ Others
Hypothalamus, Septal Nuclei, Substantia Innominata
Midbrain Limbic Area
48. īĄ fornix
ī§ from Pyramidal Neurons of hippocampus & subiculum
īĄ Precommissural Fornix
ī§ Nucleus Accumbens Septi
ī§ Anterior Hypothalamic Area
ī§ Medial Surface of Frontal Lobe
ī§ Anterior Olfactory Nucleus
īĄ Postcommissural Fornix
ī§ to Mammillary Body
ī§ Anterior Thalamus
ī§ Hypothalamus
ī§ Bed Nucleus of Stria Terminalis
49. īĄ attention and alertness
īĄ Stimulation of the hippocampus in animals
ī§ glancing and searching movements
ī§ bewilderment and anxiety
īĄ Unilateral ablation of the hippocampus in humans
does not affect memory to a significant degree
50. īĄ declarative (explicit) memoryī facts, words, and
data that can be brought to mind and consciously
inspected
īĄ plays a time-limited role (being needed only for
recently acquired information)
51. īĄ Episodic memory ī more severely disrupted than
semantic memory
ī§ left hippocampus ī verbal memory
ī§ right hippocampus ī nonverbal memory
52. īĄ low threshold for epileptic activity
īĄ spread of such epileptic activity to the nonspecific
thalamic system, and hence all over the cortex, is
not usual
53. ī CA1 ī NMDA receptors.
ī dentate hilus ,CA3 sector ī kainate receptors
ī Activation by glutamate ī entry of calcium ions into
the pyramidal neurons
ī The pyramidal neurons of these sectors contain very
little calcium-buffering protein
ī repeated activation of these pyramidal neurons
could result in cell death.
54. ī 75% of the complex partial seizures arise in the temporal lobe;
the remainder arise in the frontal lobe
ī Seizures might arise in the temporal neocortex, majority arise
in the mesial temporal structures, particularly the hippocampus
ī The hippocampus has a low threshold for seizure discharge;
consequently, stimulation of any region that supplies
hippocampal afferents or stimulation of the hippocampus itself
might produce seizures
ī Hippocampal stimulation ī respiratory and cardiovascular
changes, as well as automatisms (stereotyped movements)
involving the face, limb, and trunk
55. īĄ critical age during infancy and early childhood for
the acquisition of the pathology
īĄ There might be an age-related remodeling of
intrinsic hippocampal connections
56. ī§ anterior thalamic nuclei
ī§ contralateral and ipsilateral cingulate cortex
ī§ temporal lobe via the cingulum bundle
ī§ corpus striatum and most of the subcortical limbic
nuclei.
57. īĄ The cingulate
cortex is
continuous
with the
parahippocamp
al gyrus at the
isthmus behind
the splenium of
the corpus
callosum.
58. īĄ Stimulation ī respiratory, vascular, and visceral
changes, but changes less than hypothalamic
stimulation.
īĄ Interruption of the cingulum bundle, which lies deep
to the cingulate cortex and the parahippocampal
gyrus, has been proposed as a less devastating way
to produce the effects of prefrontal lobotomy
without a major reduction in intellectual capacity
60. īĄ tip of the temporal lobe beneath the cortex of
the uncus and rostral to the hippocampus and
the inferior horn of the lateral ventricle.
61.
62. īĄ Corticomedial - central : small ,phylogenetically
older
ī§ connections with the phylogenetically older
regions -olfactory bulb, hypothalamus, and brain
stem
īĄ Basolateral : larger , phylogenetically recent
ī§ connections with the cerebral cortex
ī§ intimately and reciprocally connected with the
prefrontal cortex via the uncinate fasciculus
67. Extended Amygdala
Connections
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
Extended Amygdala
- bridging cell groups directly
interconnects amygdaloid
and bed nucleus of stria
terminalis (BST)
which refered to as
Extended amygdala.
69. ī exteroceptive afferents :olfactory, somatosensory,
auditory, and visual) for integration with interoceptive
stimuli from a variety of autonomic areas
(1) prefrontal, temporal, occipital, and insular
corticesī highly processed somatosensory, auditory,
and visual sensory information from modality-specific
and multimodal association areas as well as visceral
information
(2) the thalamus (dorsomedial nucleus)
(3) the olfactory cortex
(4) cholinergic input from the nucleus basalis of Meynert
70. īĄ Mostly terminate in nuclei that regulate
endocrine and autonomic function, and others
are directed to the neocortex
71. īĄ The two amygdala communicate with each other
through the stria terminalis and the anterior
commissure
īĄ Nuclear groups within each amygdaloid nuclear
complex communicate with each other via short
fiber systems
72. ī AUTONOMIC EFFECTS
ī heart rate, respiration, BP, and gastric motility
ī Stimulation ī Both increase and decrease
depending on the.
73. ī ORIENTING RESPONSE
ī Stimulation ī enhances the orienting response to
novel events.
ī Animals with amygdalar lesions manifest reduced
responsiveness to novel events in the visual
environment
ī Their responsiveness, however, is improved if they
are rewarded for the response.
74. īĄ corticomedial nuclear group
ī§ Lesionī aphagia, decreased emotional tone, fear,
sadness, and aggression
ī§ Stimulation ī defensive and aggressive reaction
īĄ basolateral nuclear group
ī§ Lesionī hyperphagia, happiness, and pleasure
reactions.
ī§ Stimulation ī fear and flight.
75. īĄ attack behavior
ī§ Amygdalar stimulation ī gradual buildup and
gradual subsidence upon the onset and cessation
of stimulation.
ī§ Hypothalamic stimulationī begins and subsides
almost immediately after the onset and cessation
of the stimulus.
īĄ prior septal stimulation prevents aggressive
behavior of both amygdala and hypothalamus
stimulation
76. īĄ link the perception of the face to the retrieval of
knowledge about its emotional and social meaning.
ī Bilateral amygdalar lesions ī alteration in social behavior
and social cognition, especially as related to the
recognition of social cues from faces,impaired recognition
of facial expressions
ī Functional imaging studies ī activation of the amygdala
during presentation of emotional facial expressions
ī for negatively valenced emotions (fear, anger, and
sadness).
77. īĄ Stimulation of the basolateral nuclear group of the
amygdala ī arousal response that is similar to but
independent of that of ARAS.
īĄ Stimulation of the corticomedial nuclear group of
the amygdala, by contrast, produces the reverse
effect (a decrease in arousal and sleep).
īĄ The net total effect of the amygdala, however, is
facilitatory
78. īĄ contains the highest density of receptors for sex
hormones
īĄ Stimulation ī erection, ejaculation, copulatory
movements, and ovulation
īĄ Bilateral lesions of the amygdala produce
hypersexuality and perverted sexual behavior.
79. īĄ Stimulation CMN group ī complex rhythmic
movements related to eating, such as chewing,
smacking of the lips, licking, and swallowing
īĄ Electric stimulation of the amygdala elicits
defensive or fear-related behavior
īĄ The amygdaloid projections to the hypothalamus
via the ventral amygdalofugal pathway seem to be
essential for fear-related behavior
80. īĄ low threshold for electrical dischargesī
focus of seizures.
īĄ kindling
īĄ CPS : oral and licking movements with a loss
of conscious activity
81. īĄ Stimulation of the amygdala during brain
surgery ī autonomic and emotional reactions
,feeling of fear and anxiety, dÊjà vu
īĄ Destruction of both amygdalas ī relieve
intractable epilepsy and treat violent behavior.
ī§ Such patients usually become complacent
and sedate and show significant changes in
emotional behavior
82. īĄstructures deep to the anterior perforating substance
īĄ OlfactoryTubercle
īĄ Substantia Innominata
īĄ Basal Nucleus of Meynert
īĄ Ventral Pallidum
īĄ - non cholinergic portions of the substantia innominata
īĄ - part of limbic basal ganglia
86. Mammillary bodies
Other hypothalamic nuclei
Septal nuclei
Substantia innominata
(Basal nucleus of Meynert)
Hippocampal Formation
(hippocampus
and dentate gyrus)
Anterior Thalamic
nuclear group
Cortex of Cingulate GyrusParahippocampal Gyrus
Neocortex
Fornix
Mammillothalamic
tract
87. Memory
âĸ Short-term memory
â The information is accessed via temporary
links or associations formed in the
hippocampus.
âĸ Long-term memory
â The links in the hippocampus are replaced
by more permanent connections within the
cerebral cortex itself.
âĸ Both types of memories involve the
storage of information in the cerebral
cortex.
89. Memory
âĸ Hippocampus
â Essential for acquiring new long-tern
memories, but not for maintaining them.
âĸ Amygdala
â Formation and storage of memories
associated with emotional events.
â Involved in the modulation of memory
consolidation.
91. īĄ sudden memory loss of recent events, transient
inability to retain new information (anterograde
amnesia), retrograde amnesia of variable extension.
īĄ Complete recovery within a few hours.
īĄ epilepsy, migraine headache, and tumor.
īĄ bilateral transient ischemia of medial temporal
structures
īĄ spreading cortical depression in medial temporal
structures
92. ī amygdala, hippocampal formation, and adjacent
neural structures.
ī Visual agnosia or psychic blindness
ī Hyperorality
ī Hypersexuality
ī Lack of emotional response, blunted affect, and
apathy.
ī Increased appetite
ī Memory deficit.
93. ī disorganized thought processes, hallucinations,
delusions, and cognitive deficits.
ī Vulnerability to schizophrenia is 60% genetic and 40%
environmental.
ī Cytoarchitectural studies in schizophrenic brains point
to abnormal laminar organization in limbic structures
that are suggestive of abnormal neuronal migration
during brain development
94. ī atrophic gyri and widened sulci most prominent in
the limbic cortex
ī Association cortices are heavily affected,
primary sensory cortices are minimally affected and
the motor cortex is least affected.
96. īĄ severe focal necrotizing process with a predilection
for the limbic system
īĄ intranuclear viral inclusions (Cowdry type A
inclusions) and inflammation within limbic
structures
97. īĄ Thiamine deficiency ī mammilary body
īĄ Infarcts of the medial or anterior thalamic areas
īĄ mammillothalamic tract
īĄ Tumors of the posterior hypothalamus.
īĄ Lesions in the fornix .
īĄ corpus callosum
īĄ Lesions of the basal forebrain
98. Two basic approaches:
1. transcortical: image guidance is very helpful
īĄ A. Niemeyer approach: 2-3 cm longitudinal cortical
incision through the middle temporal gyrus centered at
a point â 4 cm posterior to the temporal tip
īĄ B. approach through the anterior superior temporal
gyrus
2. transsylvian: approach advocated byYasargil. More
restrictive and greater risk of injury to M1 portion of
MCA within sylvian fissure
īĄ Complications: vascular injury is the most significant
risk.
99. īĄ The major psychiatric diagnostic groups that might
benefit from cingulotomy are
1. chronic anxiety states, including OCD, and
2. major affective disorder (i.e., major depression or
bipolar disorder).
īĄ Oblique coronal MR images are obtained and
typically, target coordinates are calculated for a
point in the anterior cingulate gyrus 2 to 2.5 cm
posterior to the tip of the frontal horn, 7 mm from
the midline, and 2 to 3 mm above the corpus
callosum bilaterally
100. īĄ Stephen G.Waxman, MD, PhD;
ClinicalNeuroanatomy,Twenty-Sixth Edition
īĄ Snell, Richard S; Clinical Neuroanatomy, 7th Edition
īĄ T. Scarabino,U. Salvolini ;Atlas of Morphology and Functional
Anatomy of the brain
īĄ Stanley Jacobson, Elliott M Marcus; Neuroanatomy for the
Neuroscientist
īĄ Charles R. Noback, Norman L. Strominger;The Human
Nervous System Structure and Function , sixth edition