Limbic System Flashcards
2 sulci of the limbic system
Rhinal - anterior
Collateral - posterior
Papez circuitry
Hippocampus to mamillary bodies via fornix…mammillary bodies to anterior nucleus via mammillo-thalamic tract…anterior nucleus to cingulate cortex via anterior limb of IC…Cortex to hippocampal region via fornix
Entorhinal cortex
Piriform cortex
Perirhinal cortex
Entorhinal is part of parahippocampal gyrus
Prifirom and perirhinal cortices both relatred to olfaction
Orbitofrontal cortex role
Planning, decision mking and reinforcement of affective value
Regulates planning behvaior with sensitivoty to reward/[unishment
Cingulate gyrus and the cingulum
Cingulum is route form neocrotex into the hippocampus
Hippocampal formation
Key compoennts in long term meoryr consolidation and retention
Parts of the hippocampus
Lateral (bodering inferiro orn of the lateral ventricle)…hippocampus
Dentate is in between
Subiculum is most medial
Main input to hippocampus from the cortex is from the
Perforant pathway - this comes from the entorhinal cortex
Entorhinal cortex receives cortical information from the cingulum
Main input to hippocampus from subcortical areas is the
Fornix
Cell bodies arise from glutaminergic cell bodies in the subiculum
Also carries cholinergic inputs from the septal nuclei to the hippocampus nd dentate gyris
Crus
Body
Columns
Hippocampal commissure
Crus - part that enters and exits the hippocampal foramtion
Body - arching midlin
Columns - input to the thalamus/hypthalamus (postcommissural) and septal nuclei (precommisual)
Basal nucleus of meynert
Main cholinergic inputs to the hippocampus and neocrotex
Septal nuclei
Cholinergic nucleus that helps facilitate memory consolidation
Input from amygdala (via stria terminalis)
Working memory
Short term memory
LT memory
Wokring - associated with prefrontal cortex
ST - hippocampal circuits
LT - hippocamapl that receive info from all association cortices
Papez circuit type of memory
Explicit or declarative memory
Regions affected in ALzheimers
Medial and temporal lobes
As stages progress, becomes worse
Neuroimaging in Alz
In mild, atrophy of hippocampus and entorhinal cortex
High amyloid binding and hypometabolisn in the cingulate gyrus, precuneus and prefrontal crotex
Olfactory system
Sensory are in the mucosa of the roof of the nasal cavity
Mitral cell axons form olfactory tract
Anterior olfactory nucleus helps modulate
Medial and lateral olfactory stria
Medial - modify output from contralateral bulb
Lateral - raminder of output to the parahippocampal gyrus and directly to amygdfala
Piriform cortex
Projects directly to the thalamus and responsible for perception and discrimination of odors
Projects to hippocampal formation along with perirhinal to bring memory into pathway
Amygdala outputs to subcortcial structures
Stria terminalis to hypothalamus, thalamus and septal nuclei
Ventral amygdalogufal pathway to the basal forebain (ncuelus accumbens, basal of meynert)…these forebrain can go to hippocampus
Amygdala output to cortcial structures
Ventral amygdalofugal pathway to cingulate gyrus and orbitofrontal cortex to allow influences on behavior
Also to thalamus
Vnetral tegmentral area
Dopaminergic
Input from amygdala
Output to nucleus accumbens and prefrontal cortex
Nucleus accumbens
Input from VTA
Output to prefrontal cortex and cingulate gyrus
Mesocrotcial pathway
VTA projections directly to prefrontal and orbitofrontal cortex
Role in frontal lobe executive function
Too little DA
Negative signs because of too little in the mesocortical pathway
Mesolimbic pathway
VTA dopaminergic to limbic like amygdala, nucleus accumbens, hippocampus via amygdalofugal pathway
Increases activation of the limbic system
Also indicrrect because the nucleus accumbens projects to the PFC as a GABAnergic…when stimulated by VTA, it inhibits PFC
Too much dopamine
Positive signs due to increased dopamine in the mesolimbic pathway
