Limbic System Flashcards
Limbic System includes
hippocampal formation, amygdala, septal nuclei, cingulate cortex, entorhinal cortex, perirhinal cortex, parahippocampal cortex
Hippocampal Formation is located in the
temporal lobe
Hippocampal components:
Subiculum, Hippocampus proper, Dentate gyrus
WHat 2 hippocampal structures form an interlocking C
Hippocampal proper and dentate gyrus
Paleocortex and the hippocampus
Old cortex, 3-layered structure
Inside out Hippocampus meaning
the cortical layers begin with an inner molecular layer and outer polymorphic layer
The middle layer varies between dentate and hippocampus
Hippocampus - pyramidal, dentate gyrus - granule
CA3
area of hippocampus that is capped by the dentate gyrus
Alveus
the polymorphic layer of the hippocampus (white matter of neocortex) that forms the fornix
Subiculum
transitional layer between hippocampus and parahippocampal gyrus (6-layer)
Functions of the hippocampus
Short-term memory loss and inability to learn new tasks or facts
Anterograde memory loss
after lesion to hippocampus, short-term memories cannot be retained
Korsakoff’s Syndrome
Alcoholism and thiamine deficiency cause mammillary body destruction, patients cannot form new memories
Fornix
major pathway of exit/entrance to the hippocampus
Fimbria of fornix
travel posteriorly as a tight bundle of fibers of the alveus
Crura of the Hippocampus
extension of the fimbria that extends superiorly to the hippocampal commissure
Hippocampal commissure
provides 1 of 2 major pathways for hippocampi communication
Body of the Fornix
single fiber bundle from the hippocampal commissure to the anterior commissure
As the fornix reaches the anterior commissure, the fornix spits into 3:
Precommissural fornix, Decussation at the anterior commissure, and the Postcommissural fornix
Precommissural fornix fibers project to
Septal nuclei, ventral striatum, and cingulate cortex
Fibers decussating in the anterior commissure
provides the other major pathway for hippocampi communication between contralateral hippocampus
Postcommissural fornix fibers project to
Mammillary bodies and anterior nucleus of thalamus
Amygdala Location
mediodorsal portion of temporal lobe (deep to uncut, anterior to hippocampus)
Amygdala function
integrative center for emotions, emotional behavior, and motivation
Major input to amygdala
Visceral input from hypothalamus, septal areas, orbital cortex, parabrachial nucleus, olfactory bulb, temporal and anterior cingulate gyrus
Ventral Amygdalofugal output pathway of the amygdala function
motivation and drive influences on response, learned responses, stimulus-response associative learning
Stria Terminalis output pathway of the amygdala function
to septal and hypothalamus; communicate among anterior commissure
Amygdala functions
intense emotions, like fear and aggression
Amygdala lesion can result in
tameness and placid calmness
Urbach-Wiethe disease
lesion to amygdala due to Ca deposition = inability to discriminate emotion in facial expressions (facial recognition intact)
Afferents to the Septal area
hippocampal formation via the fornix, and amygdala via stria terminalis
Efferents form the Septal area
MFB to hypothalamus and midbrain tegmentum
Septal Nuclei function
PLEASURE CENTER (sex, food drive)
Lesion to septal nuclei =
loss of libido and foraging behavior
Prefrontal Cortex Location
Area 9, 12 connected to other association cortices
Prefrontal Cortex Function
judgement and foresight
Cingulate Gyrus Function
ANS (PNS activity increased) and Somatic effects (arrest behavior)
Anterior Cingulate Gyrus Function
aggression
Anterior Nucleus of the Thalamus
hypothalamus/MTT and hippocampus/fornix –> anterior nucleus –> cingulate gyrus
Dorsomedial Nucleus of the Thalamus
amygdala and prefrontal cortex –> dorsomedial nucleus –> prefrontal cortex
Substantia Innominata in forebrain
cholinergic neurons that connect limbic system and neocortex
Alzheimer’s disease shows marked cell loss of
Substantia innominata
Nucleus Accumbens in forbrain
Caudate and putamen are continuous
Nucleus Accumbens function
connection between motivational state and motor behavior
Addictions are formed by
Nucleus Accumbens
Papex Circuit
limbic system pathway for cortical control of learning and memory, emotion, and social behavior
Storing memory involves
PAPEZ Circuit
