Sist Limbico
Transcript of Sist Limbico
The Limbic System
Dr. Kenira J. Thompson
Ponce School of Medicine
Dept. of Physiology
840-2575 Ext. 2166
Email: [email protected]
Lecture Goals• Review functional anatomy of the limbic system• Describe behavior and cognitive disturbances associated
with limbic system pathology.
“Is emotion a magic product, or is it a physiological process which depends on an anatomic process?”
(Papez, 1937).
Broca’s Limbic Lobe, 1878(“Le Grand Lobe Limbique”)
C’est magnifique!
Limbic Functions (HOME)
• Homeostatic functions (autonomic and endocrine control)
• Olfaction• Memory• Emotions and Drives
What is the limbic system?
• Set of interconnected cortical and subcortical structures that form a border (or limbus) around the brain stem.
Limbicsystem
Sensory-motorsystems
Hypothal
Main Components• Limbic cortex
– Parahippocampal gyrus, cingulate gyrus, Medial Orbitofrontal cortex• Hippocampal formation
– Dentate gyrus, hippocampus, subiculum• Amygdala• Olfactory cortex• Diencephalon
– Hypothalamus, thalamus (anterior nucleus, mediodorsal nucleus)• Basal Ganglia
– Ventral striatum (Nucleus Accumbens, Caudate, Putamen)• Basal forebrain• Septal nuclei• Brainstem• Also includes the tracts that link these structures: fornix, mammillothalamic,
stria terminalis, etc.
Papez Circuit
• James Papez (1937)– Was the first to identify that emotion is not a function of any
specific brain center but a circuit involving 4 basic structures.
Revised Papez Circuit
• Paul McLean (1970)-– Revised Papez’s theory and called the circuit the limbic system.– Added more structures to the system:
• Prefrontal cortex• Parahippocampal gyrus• Important subcortical structures (amygdala, thalamic nuclei, septal
area, etc.).
Cingulate cortex
Neocortex
HippocampusAnterior nuclei of Thalamus
Hypothalamus
Emotional experience
fornix
Emotional expression
Three limbic circuits
• Amygdala-Hippocampus– Affects behaviors related to self-preservation
• Cingulate gyrus- septum– Relates to pleasure, especially sexual enjoyment (stimulation of
this region in rats results in penile erection, self-grooming)
• Hypothalamus-anterior thalamus– Important for cooperative social behavior
Cingulate Gyrus
CC
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CAUDATE
CINGULATE
Anterior nucleus thalamus
Mamillary bodies
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Parahippocampal gyrus
Fornix
Cingulate Gyrus and Depression
Depressed Patient After Fluoxetine
Hypothalamus
Damage to hypothalamicnuclei results in:Abnormalities in motivatedbehaviors such as feeding, drinking, sexual behavior,fighting, temp. regulation.
Also regulates secretion of hormones via the pituitary gland (secretions control other endocrine organs, such as the thyroid, adrenal glands, ovaries, testes).
Brain transections and sham rage
Rage reaction in cats with hypothalamic stimulation
Korsakoff’s Syndrome
• Severe anterograde amnesia• Results from thyamine deficiency (Vit. B1)• Usually caused by alcoholism• Severe degeneration of mammillary bodies.• Patients tend to confabulate to cover up memory deficit
Amygdala• Buried within the anterior-inferiortemporal lobe.
• Essential in the control of:love, friendliness, affection,fear, rage, aggression.
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Amygdala
P
H
TemporalLobe
Fx
TEMPORALLOBE
STRIA TERMINALIS
Amygdala Nuclei
Amygdala Projections
Amygdala Lesions
• Result in:– Reduced ability to identify motivational and emotional
significance of events– Electrical stimulation of amygdala can lead to emotional attacks
(rage)– Rabies virus (especially attacks the temporal lobe) leads to violent
behavior
Kluver-Bucy Syndrome• Results from bilateral removal of the amygdala and
inferior temporal cortex. Includes:– Tameness, loss of fear– Indiscriminate dietary behavior– Greatly increased autoerotic sexual activity– Tendency to attend to every visual stimulus– Tendency to examine all objects by mouth– Visual agnosia (cannot recognize objects visually)– Inability to recognize facial expression
Human brain activity in response to emotional stimuli
Amygdala activity associated with enhanced emotional memory
Neural circuit for learned fear
Tone Auditory cortex
BLA
Central nucleus
Hypothalamus
PAG
Cerebral cortex
(Autonomic Response)
(BehavioralReaction)
(Emotional Experience)
A neural circuit for aggression
Emotion and Memory
Hippocampal formation…why is it important?
• Making new memories• Involved in severe mental illness
– Reduced volume in schizophrenia, PTSD, depression
• Directly affected by estrogen (Wooley, NWU)
• Neurogenesis
Hippocampus
Mamm
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TemporalLobe
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PHG
Mammilothalamic tract
Hippocampus (cortical connections)
Neurogenesis
Hippocampus and Alzheimer’s Disease
Ischemia
Hippocampus and Depression
Hippocampus and Estrogen
Reward System Projections
This will makeme famous!
DOPAMINE
Self-stimulationReward pathways
Nucleus Accumbens
CP
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Dopamine receptors (D3) in Nuc. Accumbens
Cocaine Addict