S14 Neuro Limbic System Flashcards
Limbic system overal functions
survival instincts (innate behavior)
memory (making new memories)
behavioral and emotional expression
limbic system pathologically linked to
encephalopathy
epilepsy
cognitive deficity
psychotic symptoms (schizophrenia)
Major components of the limbic system
Medial and basal forebrain
- septal area and ventral stratum
Hippocampal formation:
- hippocampus proper, dentate gyrus and subiculum
limbic lobe:
- parahippocampus gyrus and the amygdala
amygdala hippocampus (indexer) fornix hypothalamus thalamus (anterior) cingulate gyrus olfcatory cortex entorhinal cortex
cingulate gyrus
three layered cortex
communicates with thalamus and hippocampus
Part of the Paper circuit (memory)
involved with sensory input concerning emotions
regulation of aggressive behavior
anterior part size is smaller in people with schizophrenia
Amygdala
Large, almond shape, nuclear mass
- anterior and medial temporal lobe
substantia innominata (basilar nucleus of meynert)
- origin of primary cholinergic system of the basilar forebrain
- affected in Alzheimer’s disease
Emotional responses
Memory
- Fear conditioning (associative learning process by which we learn to fear some thing)
fear and threat detection
- stimulus 1+ stimulus 2
- adoptive behavioral relationship
- re-enforcement
processing positive stimuli
emotional, more vivid memory
implicit (unconscious) kind of memory
Hippocampus
2 layered allocortex
- dentate gyrus
- Ammon’s horn
- subiculum
memory index
sends memory for remote storage
decides the site of storage
retrieve the memory when necessary
Fornix
band that connects hippocampus to the thalamus
Mammillary bodies (corpus mamillare)
part of diencephalon
2 rounded small bodies
located at the end of the anterior arch of fornix
Important for recollective memory
Damaged with Thiamine (B1) deficiency
Hypothalamus nuclei
Anterior nuclei
- Preoptic & supraoptic
Posterior nuclei
- Mammillary nuclei
Middle group
- Medial and lateral
+Orexin (hypocretin) releasing neurons (lateral)
=Regulates wakefulness and appetite
Hypothalamus parasympathetic control
anterior and medial nuclear groups
hypothalamus sympathetic control
posterior and lateral nuclear groups
hypothalamus portion of the diencephalon
wakeful
emotional center
- angry
- unhappy
behavior
motivation
Lateral hypothalamus
stimulation
- excessive eating
destruction (lesion)
- anorexia and emaciation
Ventromedial hypothalamus nucleus
- destruction (lesion)
+ hyperphagia (excessive eating) asa nearly symptom
Mating driving- humans
Originate in deep frontal lobe structures of the anterior cingulate gyrus and the septal nuclei
Significantly modified by inhibitory input from the temporal lobe limbic structures
Learned social behavioral patterns that develops in the cortex
- Forms another controlling influence of sexual behavior in humans
Libido
deep midline limbic structures
midline limbic structures
- cingulate gyrus
- septal nuclei
- hypothalamus
- limbic midbrain structures
- possibly anterior thalamus
Prefrontral lobectomy
- uninhibited sexual interest and behavior
removal of temporal lobes (Kluver-Buccy Syndrome)
- inappropriate and exaggerated sexual activity
chronic, subclinical, stimulation of the temporal lobes
- global hypo sexuality
Fighting and fleeing
Function of limbic system - temporal lobe \+ amygdala \+ hippocampus - hypothalamus (modulator)
stimulation of the amygdala or hippocampus-> violent attack behavior in Monkeys
- similar behavior seen in
+ temporal lobe epilepsy
+ destructive lesions to ventromedial hypothalamus
memory network/areas
medial temporal lobes
- hippocampus
- amygdala
basal forebrain
diencephalone
- dorsomedial and paramedian thalamic nuclei
- maxillary bodies
Memory and limbic system
mamillothalamic tract
mamilllothalamic tract
mammillary bodies-> anterior nucleus of the thalamus-> cingulate gyrus
Papez circuit
mammillary bodies-(mamillothalamic)-> anterior thalami -(internal capsule)-> cingulate- (cingulum)-> amygdala hippocampus -(fornix)->
amnesia
inability to learn new information:
- disorder of recent memory
- involves the medial temporal lobes, diencephalon and basal forebrain
- amygdala may assign emotional significance to signals prior to processing in hippocampus
limbic dysfunction and Amnesia possible causes
limbic encephalitis
- infectious:
+ herpes simplex virus
- immune/inflammatory + paraneoplastic
+ autoimmune
Amnesia:
- transient global amnesia
- anoxic encephalopathy
- traumatic brain injury
- stroke (PCA stroke)
- Diencephalic tumors
- Alzheimer’s disease
- Korsakoff’s psychosis
Wernicke’s encephalopathy
- triad of:
+ acute mental confusion (encephalopathy)
+ Ataxia (cerebellar involvement)
+ ophthalmoplegia (diplopia) - Korsakoff Amnestic syndrome is a late neuropsychiatric manifestation
+ retrograde and anterograde amnesia
+ confabulation - thiamine (B1) deficiency
+ works as coenzyme in metabolism of glucose and lipid
+ LA and failure of energy-> cellular death - early recognition and treatment
+ resolution of symptoms within hours - alcoholics
+ alcohol affects B1 uptake and utilization
-none alcoholics \+ hyperemesis gravidarum \+ bariatric surgery (bariatric beriberi) \+ prolonged starvation \+ HIV/ AIDS \+ infants fed thiamine deficient formula \+ iatrogenic exacerbation = prolonged glucose or carbohydrate loading in a person with marginal deficiency
Kluver-Bucy syndrome
areas involved:
- bilateral lesions of the medial temporal lobes
- including the amygdaloid nucleus
symptoms:
- amnesia (retrograde and anterograde)
- hyperplasia and hyperorality
- hyper sexuality
- diminished fear responses (placidity)
- visual agnosia
+ inability to recognize familiar objects or people
Kluver-bucy syndrome- damage to the bilateral medial temporal lobes
temporal lobectomy
meningoencephalitis (herpes encephalitis)
traumatic brain injury
brain tumors
ischemic/anoxic (stroke)
conscious appreciation of an emotion: positive feelings
frontal cortex/ septal nuclei/ cingulate gyrus
conscious appreciation of an emotion: negative feelings
temporal lobe cortex/ amygdala/hippocampus
conscious appreciation of an emotion cortical phenomena
- cingulate and phylogenetically order limbic cortex
- entire cortex will participate in fully emotional experience
