Limbic System Anatomy Flashcards
Limbic lobe
Consists of the cingulate gyrus, isthmus, parahippocampal gyrus, and subcallosal gyrus
Prefrontal cortex components
Dorsolateral PFC
Ventrolateral PFC
Medial PFC
Orbitofrontal cortex
Anterior cingulate cortex
Major functions of the PFC?
Attention, concentration, executive control
The Cingulum
A fiber bundle that projects from the cingulate gyrus to the entorrhinal cortex in the temporal lobe, also projects to the amygdala . Receives input from the thalamus (which receives input from the spinothalamic tract about pain/temp). Reinforces behaviors that reduce pain.
Where does the entorrhinal cortex project to?
The hippocampal formation
Components of the hippocampal formation
Hippocampus and dentate gyrus.
Main output structure from hippocampal formation
Subiculum
Order of processing from entorhinal cortex through hippocampal formation
Entorhinal cortex ->dentate gyrus -> CA3
Projections of CA3
1) Via precommissural fornix to septal nuclei, ventral striatum (Accumbens and olfactory tubercle).
2) Via shaffer collaterals to CA1, which projects to the subiculum
Where does the subiculum project?
Via the postcommissural fornix to the mammillary bodies
Bilateral hippocampi removal?
Anterograde amnesia
Effect of AD on hippocampus?
Shrinks
Frontotemporal dementia symptoms
Dramatic changes in personality, socially inappropriate behavior, impulsivity, emotional indifference, language deficits.
Hippocampal place cells
Generate a map of the environment
Where do the mamillary bodies project after receiving input from postcomissural fornix?
Back to the thalamus (anterior group), which projects back to the cingulate cortex.
Function of the basal forebrain, septal nuclear complex, ventral striatum
Memory, cognition, reward.. These are cholinergic systems.
Cholinergic projection from septal nuclei to the hippocampus?
Via the fornix, important for cognition.
Amygdala structure
Has basal and lateral nuclei, then central and edial nuclei
Function of the amygdala
Learning associated with fear, memories associated with fear. Important in memory/cognition. Also, major epileptic focus.
Kluver Bucy Syndrome
Bilateral lesions of the amygdala produce placidity, loss of fear, hypersexuality, and hyperphagia.
Two main output pathways from the amygdala
The Ventral Amygdalo-fugal pathway - projects to the basal forebrain, hypothalamus, ventral striatum, and thalamus
(regulates emotional tone)
Stria terminalis and its bed nucleus- Important for sex, control of eating, and anterior pituitary control.
HPA axis and limbic control
Controls cortisol secretion from the adrenal cortex, Hippocampus: inhibition. Amygdala: Excitation.
Olfactory cortex and its association with the limbic system
Very strong. No thalamic relay.
Two main dopaminergic limbic pathways
Mesolimbic- from VTA to NAS via median forebrain bundle. Mediates reward
Mesocortical pathway- From VTA to DLPFC, VMPFC, ACC, Olfactory bulb. Mediates cognition, memory, and emotion.
