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LIMBIC SYSTEM. History. Paul Broca (1824-1880): 1878: “ le grand lobe limbique ” Refers to a ring of gray matter on the medial aspect of the cerebral hemispheres. James Papez (1883-1958):
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History • Paul Broca (1824-1880): 1878: “le grand lobe limbique” Refers to a ring of gray matter on the medial aspect of the cerebral hemispheres. • James Papez (1883-1958): 1930’s: defined a limbic system that might underlie the relationship between emotion and memory (Papez’ circuit).
Components • Amygdaloid body • Hippocampus (“seahorse”) • Cingulate gyus • Parahippocampal gyrus • Hypothalamus • Mamillary bodies • Anterior nucleus of thalamus
Functions • “Emotional brain Emotional and motivational aspects of behavior. Provides emotional component to learning process: Especially the amygdala. • Associated with memory Especially the hippocampus. • Associated with pain/pleasure, rage
Amygdala • Large nuclear group in temporal lobe. • Afferents: Olfactory tract Solitary nucleus Parabrachial nucleus Limbic neocortex: Cingulate gyrus Parahippocampal gyrus
Amygdala Connections Cerebral cortex Olfactory system Thalamus Brainstem reticular formation Hypothalamus Stria terminalis AMYGDALA Ventral Amygdalofugal fibers
Regions of the Amygdala • Large basolateral region: Provides direct input to basal ganglia and motor system. • Small corticomedial group of nuclei: Related to olfactory cortex. • Medial and central nuclei: Connected to hypothalamus.
Amygdala Inputs Olfactory System AMYGDALA Corticomedial Nuclear Group Temporal Lobe (associated with visual, auditory, tactile senses) Basolateral Nuclear Group Central Nucleus Brainstem (viscerosensory relay Nuclei: solitary nucleus and parbrachial nucleus) Ventral Amygdalofugal Fibers
Amygdala Outputs Stria Terminalis Septal Nuclei Hypothalamus AMYGDALA Corticomedial Nuclear Group Dorsal Medial Thalamic Nucleus Nucleus Accumbens Hypothalamus Basolateral Nuclear Group Central Nucleus Ventral Amygdalofugal Fibers Nuclei of ANS Ventral Amygdalofugal Fibers
Functions of the Amygdala • Relate environmental stimuli to coordinated behavioral autonomic and endocrine responses seen in species-preservation. • Responses include: Feeding and drinking Agnostic (fighting) behavior Mating and maternal care Responses to physical or emotional stresses.
Limbic System and Basal Nuclei Anterior Cingulate Gyrus Orbitofrontal Areas (10, 11) Medial and lateral temporal lobe Hippocampus Amygdala Entorhinal cortex (24) Ventral Striatum (nucleus accumbens) Caudate Nucleus (head) Ventral Anterior Nucleus Dorsomedial Nucleus Ventral Pallidum Medial Globus Pallidus Pars Reticularis (Substantia nigra)
Papez Circuit (Emotions) Mammillothalamic tract Fornix Mammillary bodies Other hypothalamic nuclei Septal nuclei Substantia innominata (Basal nucleus of Meynert) Hippocampal Formation (hippocampus and dentate gyrus) Anterior Thalamic nuclear group Neocortex Parahippocampal Gyrus Cortex of Cingulate Gyrus
Pathologies (lesions) • Voracious appetite • Increased (perverse) sexual activity • Docility: Loss of normal fear/anger response • Memory loss: Damage to hippocampus portion: Cells undergoing calcium-induced changes associated with memory
Kluver-Bucy Syndrome: • Results from bilateral destruction of amygdala. • Characteristics: Increase in sexual activity. Compulsive tendency to place objects in mouth. Decreased emotionality. Changes in eating behavior. Visual agnosia.