Limbic system Flashcards
What is the original path of Papez
Cingulate–> Hippocampus–> to fornix–> to mammillary bodies –> thalamus
What structures were added to Papez path
parts of hypothal, spetal area, orbitofrontal cortex, nucleus accumbens and most importantly: AMYGDALA
What justifies the concept of the limbic system
common physiological and neurochemical properties
Intricate anatomic connections
Common behavioral associations
Common Physiological and neurochemical properties of Limbic system
Herpes virus has affinity for these areas, seizure foci
neurochemical: lots of cholinergics and high density of optiate R’s key for memory/ perception of pain/ pleasure
What provides cholinergic input for the brain in the limbic system
Septal nuclei and nucleus basalis of meynert
This system is critical for positive reinforcement of brain mechanisms (drugs and pleasure)
Mesocorticolimbic Dopamine system
What connects the hippocampus and mammilary and septal nuclei
fornix
What connects the mammillary bodies to the ant. thalamus
mammilothalamic tract
What connects the Entroinal cortex to the Dentate (hippocampus)
Perforant path
What 4 structures make up the Outer Core corticl structures of the hippocampus
Cingulate gyrus, Orbital frontal lobe, subcallosal area, parts of temporal lobe(hippocampus, parahippocampal gyrus, uncus)
The cingulate cortex is part of outer core
rostrally:
caudally:
rostrally in charge of emotions and motor
caudally in charge of visual spatial and memory
Function of the ORbital frontal lobe of the outer cortical area
personality, behavioral control, self awareness
Fnx of teh temporal lobe in the outer cortex
memory
What makes up the Inner core of the limbic system
Anterio thalamic nucleus, mammillary body, hypothalmic nuclei and septal nuclei
Three sub corticla structures of limbic system
Hypothalamus
Amygdala
septum
Subcortical area in charge of pleasure, autonomic and endocrine integrations
Hypothalamus
Neurons project to pituitary and release ACTH and TSH→ involve din maternal behavior, BP, feeding, temp regulation, immune response
Hypothalamus
Amygdala fnxs in the subcortical zone
Preservation of self—behaviors, emotions, social behavior, aggression, defense reponse, sexual behavior, affective significance of visual stimuli, affects of faces, affective regulation
Preservation of self—behaviors, emotions, social behavior, aggression, defense reponse, sexual behavior, affective significance of visual stimuli, affects of faces, affective regulation
Amygdala
Preservation of species—behaviors like sex and emitonality
Septum in the subcortical zone
Septum responsibilities
Preservation of species—behaviors like sex and emitonality
Inntricate anatomic connections; most anatomic connections are
recipricol
connects hippocampus w/ septum and mammilary bodies
a. main efferent pathway
Fornix
connects amygdala with septum/hypothal/ bed nuc/ and nuc acc
Stria terminalis
Ventral amygdalofungal pathway connects amygdala with
connects amygdala with hypothalamus, brainstem and septum
Main AFFERENT to the hippocampal formation
Perforant path: connects entorhinal cortex with dentate gyrus
Medial Forebrain bundle:
connects hypothalamic nuclei and amygdala and brainstem nuclei
connects hypothalamic nuclei and amygdala and brainstem nuclei
Medial Forebrain bundle
Symptoms of Kluver Bucy in monkeys
a. Psychic blindness or visual agnosia: lost ability to detect the meaning of object based on visual criteria
b. Oral tendincies—examine all objects by mouth
c. Hypermetamorphosis—nocite and reacy to every visual stimulus: attend to every visual stimulus w/in field and then will compulsively handle the object
d. Tameness—no motor or vocal reactions with fear or anger~ can’t tell if somethings threatening
e. Hypersexuality—indiscriminate sexual advances
Bilateral large temporal lobe lesions~ including amygdala, hippocampus, uncus will cause what
Kluver Bucy
Human Kluver Bucy
increased oral activy
hypersexuality
Hypermetamorphosis
Placidity: flattened affect, lack of aggressive behavior
Visual agnosia: loss of recogniton of simple familiar objects or people
bulimia
Etiology of Kluver Bucy
a. Post tramatic encephalopathy
b. herpatic viral encephalitis or anoxia
c. subarrachnoid hemorrhage
d. picks diseaes or alzheimers
e. bilateral temporal infarction
f. focal status epilepticus
All Kluver Bucy autopsy show
extensive lesions involving bilateral temporal cortex and amygdala
sensory limbic hyperconnection—strengthening of synaptic connection
Gerschwind syndrome
Symptoms of Gerschwind
Increased concern with philosophical, cosmic, or religious issues
Altered sexual behavior—hyposexual
Hypergraphia—extensive writing that’s typically religious or philosophical in nature such as diaries, poems, essays, sermons
Viscosity—tendency towards interpersonal stickiness, hard to break off conversation
Most pleasurable regions include:
lateral hypothalamus and medial forebrain bundle (connects hypothal and septum)
______ and _______ systems are impliated in location of effective self-stimulation
Catecholamines and DA
Mesolimbic dopamine systems appears to be most important for
motivational process.
Some addictive drugs produce their potent effects on behavior by enhancing mesolimbic DA activity
- -Heroin works by
- –Cocaine works by
Heroin works by increases neuronal firing rate of DA cells
—Cocaine works by inhibits reuptake of DA
Key regions of brain of pleausre
lateral hypothal
medial forebrain bundle
Nucleus accumbens
Pain and punishment→ lesions to ventromedial nucleus of hypothalamus produces
pain, rage or srong aversive rxns and long lasting hyperemotionality
What produces RAGE
When we stimulate Dorsal Nucleus OR if Ventromedial nucleus is destructed → produces RAGE
Modulation and experience of emotional rxns~~ leads to tameness if you lose it.
Amygdala
In a study of amygdala, depth of electrode recordings show discharge in amygdala most frequently associated with affective phenomena in patients w/ ______
epilepsy
*amydala attributes affective significance to visual stimuli
Afferent and efferent conx of amygdala are strategically situated to geneate r
apid, specific autonomic and endocrine responses to complex social signs
Amygdala and social situations
Need amygdala for normal social interaction→w/out see decreased social interaction, affiliative behavior, Indiscriminate hypersexuality, devestating effect on maternal behavior
Provides emotional response to faces
amygdala
Function of Septal Regions
a. Hypersexuality seen in cats by amygdalar lesions abolished by septal lesions (positive control of sex behavior)
b. Stimulation in animals results in 400% increase of sex drive of rats as measured by crossing electrical grid to a sex incentive
Stimulation in animals results in 400% increase of sex drive of rats as measured by crossing electrical grid to a sex incentive
Septal region
Septal lesions produce
enhancement of social contacts and incresed of sexual activit
emotional affects of sepatal tumor
rage like attacks and increased irritability
Hippocampus: Lesions of dorsal medial nulceus of thalamus, mammillary nuclei alone or in combination may lead to
amnestic states
Declaritive memory
aquisition of facts and events
need dorsal medial nucelus of thalamus and the mammilary nuclei
Person events in ones life, actively remembere, embedded in time and place
Episodic—-Declaritive memory
Facts, known rather than actively remembered
Semantics—declartive memory
Hippocampal formation incldues
hippocampus, dentate gyrus, subiculum
Major effernt of hippocampal formation:
Major Afferent of hippocampal formation:
- Fornix
- Perfornith path
Hippocampal formation:
Neurons from EC project to the dentate and synapse with
granule cells, and hippocampal pryamidal cells
Neurons from EC project to dentate, synapse with granule cells, then with hippocampal pyramidal cells cells and extend toward
lateral ventricle whre they form the alveus ,then fimbria, then fornix
Crucial for formation of episodic memories in humans (record of personal events) and dedicated to spatial mapping in animals
Hippocampus
Amnesia following bilateral temporal~ removed the guys bitemporal temporal lobes and he couldn’t learn anything new and each day forgot… we also see hippocampal sclerosis and atrophy as a result of
–also see hippocampal sclerosis and atrophy as a result of temporal lobe epilepsy for a long time
supplies much of hippocampal region and get amnesia if stroke here
Stroke: Left MCA Stroke→ the Posterior cerebral artery (from basilar)
Wernicke Korsakoffs syndrome
Wernicke Korsakoffs Syndrome
d/t to chrnoic alcoholism and nutritional deficienty (thiamine)
Acute state is Wernickes encephalopathy; confusion, disorientation, oculomotor, dysnfnx, ataxia
Chronic anterograde and temporally-graded retrograde amnesia
Lesions in mammillary bdies and thalamus
Cingulate Gyrus Behavioral changes after lesions in anterior cingulate
in humans: apathy, disinhibition, placidity, depression, anxiety, OCD, heightened sexuality, bulimia
Anterior cingulate
emotion and motor fnx
Posterior cingulate
visuospatial and memory
Used to succefully tx OCD
can help chronic pain pts
narcotic withdrawl
cingulotomy
See associated sociopathy– show blunted autonimic responses to emotional stimuli
have cingulotomy
mostl commly associated with bilateral anterior cingulate cortex lesions
pts can talk, but have no desire to
akinetic mutism
Abnormalities in AC is postulated bc of its role in affective vocalizations
Gilles de la Tourette Syndrome
Lesions of AC can relieve OCD and is an associated feature of
GTS
What happens when we electircally stimulate the AC
complex coordinated movements
How can we reduces tourtettes synmptoms
disconnection of AC from thalamus
Integration of thought, motivation, and emotion with movement are critical aspects of cingulate fnx
—Anterior cingulate gyurs
Excessive amplification of emotional signals in the anterior cingulate gyrus result in
anxiety and OCD
Amplification of motor behavior in anterior cingulate results in
tics and impulsive behavior
Excessive filtering of emotios and motor behavior in the anterior cingulate result in
Apathy, akinesis, mutism
Orbital frontal lobe syndrome
Disinhibited, tactless, bawdy, boastful, grandiose, restless, impulsive, inattentive, perseverative, tendancy to dress carelessly and eat gluttonously
Disinhibited, tactless, bawdy, boastful, grandiose, restless, impulsive, inattentive, perseverative, tendancy to dress carelessly and eat gluttonously
orbitofrontal lobe syndrome
Apathetic, slow, demonstrates little initiative or spontaneity
responding in an automaton like manner, vacancy of expression
Frontal/convexity or dorsolateral syndrome
akinetic mutism, inert, speechless, with intact sleep wake cycle, “motionless, mindless, wakefulness” loss of drive to move or speak
Medial frontal syndrome
Medial frontal sydrome
akinetic mutism, inert, speechless, with intact sleep wake cycle, “motionless, mindless, wakefulness” loss of drive to move or speak
Frontal/convexity or dorsolateral syndrome
Apathetic, slow, demonstrates little initiative or spontaneity
responding in an automaton like manner, vacancy of expression
