Limbic system

What is the limbic system 

A network of ancient cortical and subcortical structures involved in emotion, memory, motivation, reward, social behaviour, and autonomic regulation.  It forms a ring around the medial rim of the cerebral hemisphere and the upper brainstem. 

Where is the limbic system

temporal lobe, medial frontal lobe, diencephalon and basal forebrain

What are the major components of the limbic system

Cingulate gyrus and cingulum bundle, parahippocampal gyrus and hippocampal formation, amygdala, fornix, hypothalamus and mammillary bodies, septal area and nucleus accumbens, anterior nucleus of the thalamus, bed nucleus of the stria terminalis

Where is the cingulate gyrus anc cingulum bundle

located superior to the corpus callosum, curving around it

where are the parahippocampal gyrus and hippocampus formation 

located on the medial temporal lobe, forming floor of the inferior horn of the lateral ventricle. Its anterior portion includes the entorhinal cortex, the primary gateway between neocortex and hippocampus 

Where is the amygdala

situated in the anterior temporal lobe, just anterior to the hippocampal head

Where is the fornix

major white-matter tract arching from the hippocampus to the mammillary bodies

septal area

midline basal forebrain structures linked to reward and drive 

What is the Bed nucleus of the stria terminalis

an extended amygdala component involved in fear, stress and sustained anxiety

additional pathways 

stria terminalis 

anygdalfugal

cigulum

medial forebrain bundle

where are the mammillary bodies

The base of the diencephalon

what do the cingulate gyrus and cingulum bundle do 

form a limbic arch above the corpus callosum. I is divided into subgenual, anterior, dorsal and posterior regions each associated with different emotional and cognitive roles. 

What is the anterior cingulate cortex involved in

pain percerption, emotional appraisal, conflict monitoring and autonomic arousal

What is the cingulum involved in

carrying information from the cingulate through the gyrus into the parahippocampal gyrus and entorhinal cortex which provides major cortical input inot the hippocampal formation.

what are cingulum 

a pair of association white matter tracts underlying each cingulate gyrus. Lesions here can alter mood and treat severe depression and OCD

What is the hippocampal formation

Lies on the floor of the inferior the lateral ventricle. It is a long sausage shaped structure lying in an antero-posterior orientation. In coronal cross section a curved internal structure to the hippocampus proper is evident comprising parts: Cornu ammonis (CA1-CA4), Dentate gyrus. The cortical areas feeding fibres from the parahippocampal gyrus include the entorhinal cortex and subiculum leading to the formation of CA1 of the hippocampal proper

What is the amygdala

It contains nuclei involved in fear, threat detection, emotional valence, social cognition and reward learning.

what can lesions in the amygdala cause

reduced fear, emotional blunting or Kluver-bucy syndrome

more on the amygdala

Its output pathway, the stria terminalis runs along the lateral ventricle toward the hypothalamus and BNST, while the ventral amygdalofugal pathway provides faster projection to the prefrontal cortex and brainstem .

what is the forinx

alveus

fimbria

crura

comissure

body

columns

which descend into mammillaries bodies and the septal area. this pathway is vital for memory consolidation

what are mammillary bodies

receive hippocampal output via the forinx and relay it to the anterior thalamic nucleus via mammilothalamic tract

What is the septal area

receives input from the hippocampus and projects back through the medial septal nucleus modulating hippocampal rhythms important for learning and navigation

What is the best known limbic pathway 

papez circuit , which links emotional experiences with memory and behaviour