LIMBIC SYSTEMLIMBIC SYSTEM

HistoryHistory

Paul Broca (1824-1880):Paul Broca (1824-1880):1878: “1878: “le grand lobe limbiquele grand lobe limbique””

Refers to a ring of gray matter on Refers to a ring of gray matter on the medial aspect of the cerebral the medial aspect of the cerebral hemispheres.hemispheres.

James Papez (1883-1958):James Papez (1883-1958):1930’s: defined a limbic system that might 1930’s: defined a limbic system that might underlie the relationship between emotion underlie the relationship between emotion and memory (Papez’ circuit).and memory (Papez’ circuit).

ComponentsComponents

Amygdaloid bodyAmygdaloid bodyHippocampus (“seahorse”)Hippocampus (“seahorse”)Cingulate gyusCingulate gyusParahippocampal gyrusParahippocampal gyrusHypothalamusHypothalamusMamillary bodiesMamillary bodiesAnterior nucleus of thalamusAnterior nucleus of thalamus

FunctionsFunctions

““Emotional brainEmotional brainEmotional and motivational aspects of Emotional and motivational aspects of

behavior.behavior.

Provides emotional component to learning Provides emotional component to learning process:process:Especially the amygdala.Especially the amygdala.

Associated with memoryAssociated with memoryEspecially the hippocampus.Especially the hippocampus.

Associated with pain/pleasure, rageAssociated with pain/pleasure, rage

AmygdalaAmygdala

Large nuclear group in temporal lobe.Large nuclear group in temporal lobe.Afferents:Afferents:

Olfactory tractOlfactory tract

Solitary nucleusSolitary nucleus

Parabrachial nucleusParabrachial nucleus

Limbic neocortex:Limbic neocortex:

Cingulate gyrusCingulate gyrus

Parahippocampal gyrusParahippocampal gyrus

Amygdala Connections

Cerebral cortexOlfactory system

ThalamusBrainstem reticular formation

Hypothalamus

AMYGDALA

Striaterminalis

Ventral Amygdalofugalfibers

Regions of the AmygdalaRegions of the Amygdala

Large basolateral region:Large basolateral region:Provides direct input to basal ganglia and Provides direct input to basal ganglia and motor system.motor system.

Small corticomedial group of nuclei:Small corticomedial group of nuclei:Related to olfactory cortex.Related to olfactory cortex.

Medial and central nuclei:Medial and central nuclei:Connected to hypothalamus.Connected to hypothalamus.

Amygdala Inputs

AMYGDALA

Corticomedial NuclearGroup

Basolateral NuclearGroup

Central Nucleus

OlfactorySystem

Temporal Lobe(associated with visual,auditory, tactile senses)

Brainstem (viscerosensory relayNuclei: solitary nucleus

and parbrachial nucleus)

VentralAmygdalofugal

Fibers

Amygdala Outputs

AMYGDALA

Corticomedial NuclearGroup

Basolateral NuclearGroup

Central Nucleus

VentralAmygdalofugal

Fibers

Septal NucleiHypothalamus

Dorsal Medial Thalamic NucleusNucleus Accumbens

Hypothalamus

Nuclei ofANS

VentralAmygdalofugal

Fibers

Stria Terminalis

Functions of the AmygdalaFunctions of the Amygdala

Relate environmental stimuli to Relate environmental stimuli to coordinated behavioral autonomic and coordinated behavioral autonomic and endocrine responses seen in species-endocrine responses seen in species-preservation.preservation.

Responses include:Responses include:Feeding and drinkingFeeding and drinking

Agnostic (fighting) behaviorAgnostic (fighting) behavior

Mating and maternal careMating and maternal care

Responses to physical or emotional stresses.Responses to physical or emotional stresses.

Limbic System and Basal Nuclei

Medial and lateral temporal lobeHippocampus

AmygdalaEntorhinal cortex (24)

Ventral Striatum(nucleus accumbens)

Caudate Nucleus(head)

Anterior Cingulate GyrusOrbitofrontal Areas (10, 11)

Ventral PallidumMedial Globus Pallidus

Pars Reticularis(Substantia nigra)

Ventral Anterior NucleusDorsomedial Nucleus

Papez Circuit (Emotions)

Mammillary bodiesOther hypothalamic nuclei

Septal nucleiSubstantia innominata

(Basal nucleus of Meynert)

Hippocampal Formation(hippocampus

and dentate gyrus)Anterior Thalamic

nuclear group

Cortex of Cingulate GyrusParahippocampal Gyrus

Neocortex

FornixMammillothalamic

tract

Pathologies (lesions)Pathologies (lesions)

Voracious appetiteVoracious appetite Increased (perverse) sexual activityIncreased (perverse) sexual activityDocility:Docility:

Loss of normal fear/anger responseLoss of normal fear/anger responseMemory loss:Memory loss:

Damage to hippocampus portion:Damage to hippocampus portion:Cells undergoing calcium-induced changes Cells undergoing calcium-induced changes associated with memoryassociated with memory

Kluver-Bucy Syndrome:Kluver-Bucy Syndrome:

Results from bilateral destruction of Results from bilateral destruction of amygdala.amygdala.

Characteristics:Characteristics:Increase in sexual activity.Increase in sexual activity.

Compulsive tendency to place objects in mouth.Compulsive tendency to place objects in mouth.

Decreased emotionality.Decreased emotionality.

Changes in eating behavior.Changes in eating behavior.

Visual agnosia.Visual agnosia.