Limbic System and cognition Flashcards
Where is the hippocampus found?
Temporal lobe
What does the limbic system do?
Mood, emotion, feeling, motivation
50% of Pxs will be there for mood disorders
Where do fibers from the hippocampus go?
Around the thalamus and to the mammillary body and also to the septal nuclei
What is the name of the fiber bundle from the hippocampus to the mammillary body and septal nucleus?
The fornix
Where is The locus cerullius and what does it make?
In the pons
Makes norepinephrine
Where is RAPHE nuclei and what is made there?
Serotonin is made there
Found in the midbrain and pons
What do arousal and sleep-wake cycle?
Norepinephrine and serotonin
What is the meso limbic system?
Reward system
In the midbrain
Dopamine
What is the nucleus of the midbrain that produces the most dopamine in the body?
The ventral tegmental area (VTA)
Where does the VTA project?
Nucleus accumbens
Medial prefrontal cortex
Amygdala
Septal nuclei
What do cocaine and amphetamine do to dopamine?
Prevent dopamine reuptake
What does a lesion in the VTA or the nucleus accumbens do?
Decrease in drug seeking behavior
Same if you give dopamine receptor blockers
What does the nucleus basalis and septal nucleus make?
ACh
What nuclei make ACh in the meso limbic system?
Nucleus basalis
Septal nucleus
First to go in Alzheimer’s
What is the role of the amygdala?
Learning, fear conditioning
What do lesions of the amygdala do?
Prevent fear conditioning
Still feel free but cannot pair neutral and bad stimulus
What does injury to the prefrontal cortex do?
Prefrontal lobe syndrome
- bad goal directed behavior
- emotionless
- responsive to criticism
- poor social judgement
What does the dorsal PFC do?
Executive function
Working memory
What does the orbital frontal cortex do?
Projects to the amygdala
What does the PFC do to the amygdala?
Via the OFC is inhibits the amygdala (normally activates the hypothalamus)
What happens with a lesion in the hippocampus?
Bilateral medial temporal lobectomy
Anterograde amnesia –> no new memories
Temp retrograde memories –> lost old
Old memories were explicit: semantic (facts) and episodic (experiences) where he was
Still had motor skills
What is Urbach-Wiethe disease?
Bilateral loss of amygdala
Impaired recognition of emotion NAND facial expressions
Inability to judge like emotions (fear vs. anger)
Emotional memory loss
What is the triad of symptoms in PTSD?
Re-experiencing the situation
Avoidance of similar situation
Hyperarousal, increase anxiety
What is the etiology of PTSD?
Increase amygdala
Decrease medial PFC
What are symptoms of schizophrenia?
Fragmentation of mood, thought and movement
Positive: delusions, hallucinations
Negative: social withdrawal
Tx only affects positive symptoms
1% of population
What is the dopamine hypothesis of schizophrenia?
Too much dopamine receptors
Haloperidol is anti dopamine, side effect is Parkinson’s motor dysfunction
Clozapine
- Block DA receptor for a small amount of time
- Block serotonin receptors
- Block glutamate reuptake
What is the basis of the glutamate hypothesis of schizophrenia?
PCP - blocks NMDA receptors
Tx: up glutamate
What are symptoms of depression?
Lethargy
Anhedonia - no pleasure in normal activities
Loss of sleep and weight
15%. (20% female, 13% male)
What is the mono amine hypothesis of depression?
Depression is due to a decrease in NE and or Serotonin receptor activity
Tx: raise those concentration in synaptic cleft
How do we block MAO and what does it do?
Block metabolism of NE or 5HT
What do tricyclics like imipramine do?
Block reuptake of NE and 5HT
What do SSRIs like Prozac (fluoxetine) do?
Block reuptake of 5HT
What is Korsakoff’s syndrome symptom wise?
3
No new memories
Disorientation of space and time
Made up stories
What causes Korsakoff’s syndrome?
Alcoholism leading to B1-thiamine def
What part of the limbic system is damaged in Korsakoff’s?
Mammillary bodies or mamallothalamic tract
What is Kluver-Bucy syndrome?
From temporal lobe damage by stroke or encephalitis
Amygdala, hippocampus, and temporal lobe bilateral
Little emotion (loss of amygdala)
Hyper sexuallality (always change it here) (damage pathways to hypothalamus)
Visual agnosia - inability to discriminate visual stimuli (think pen is food?) damage visual pathways
What is characteristic of Alzheimer’s dementia (AD)?
50% of people over 85
1st stage: loss of memory
2nd stage: mood disorder, anxiety and depression
3rd stage: loss of motor function
4th stage: complete Loss of cognitive function
What is the etiology of Alzheimer’s?
Loss of Cholinergic neurons in the nucleus basalis
Proteins NFT inside the cell and B-amyloid plaques form outside the cells
Lateral ventricles are huge because the neurons are gone?
Why treat Alzheimer’s with Aricept?
Blocks acetylcholine esterase
What is chronic traumatic encephalopathy (CTE)?
30-50year
Progressive neurodegeneration disease caused by repeated head trauma
3 symptoms:
- Cognition-anterograde amnesia, goal directed behavior (PFC)
- Mood - depression and apathy
- Behavior - impulse control is bad, aggressive
Get NFTs in amygdala and hippocampus and PFC
What is cognition?
Our internal life
Perception, memory attention language, emotion
Planning
Consciousness
The integration of many kinds of information
Gives choice of appropriate behaviors
What is the “default network?”
Involved in day dreaming or mind wandering
Autobiographical memories envisioning the future moral decisions
6 parts
- posterior parietal
- posterior cingulate
- dorsolateral prefrontal
- medial prefrontal
- medial temporal
- rostrolateral temporal
What is disturbed in mental illnesses like depression, OCD, schizophrenia, autism?
The default network
What are the “not-primary” cortexes?
Either unimodal integrating with one sensory modality
Or multimodal integrating with many
Examples are the premotor cortex, all association cortexes (visual, somatosensory, auditory)
What is the hierarchy of projections to carry out an appropriate behavioral response to a stimulus?
Primary sensory cortex –> unimodal –> multimodal –> premotor cortex –> motor cortex
What stain is used to look at the cortical lamination?
Nissl stain (6 layers)
What are stellate cells used for?
Lots of sensory information intake
In layer 4 therefore 4 is big in sensory places and small in motor
What is in layer 5 and when is it bigger/smaller?
Betz cells, large pyramidal cells
Big in motor cortexes
What is layer four?
Sense-specific thalamic nucleus
What are the four areas of the thalamus important for sense specific thalamic nucleuses?
VPL, VPM, LGN, MGN
What is the input and output of the lateral geniculate nucleus?
Input - retina
Output - primary visual cortex
What is the input and output of the medial geniculate nucleus?
Input - Cochlea via brainstem auditory nucleus
Output - primary auditory cortex
What areas of the thalamus are for multimodal thalamic nuclei? (Have a big layer 4)
Pulvinar
Medial dorsal
Lateral posterior
Anterior
What is the input and output of the Pulvinar?
Input - association cortex, superior colliculus
Output - parietotemporal and visual association cortex
Involved in putting vision to auditory cortex? And visual cortex
What is the input and output of the medial dorsal nucleus?
Input: superior colliculus, olfactory cortex, amygdala, ventral pallidum
Output: FEF, anterior cingulate cortex
What is the input and output of the lateral posterior nucleus of the thalamus?
Input: association cortex, anterior cingulate, retina
Output: parietal and visual association cortex, anterior cingulate, striatum
What is the input and output of the anterior nucleus of the thalamus?
Input: hypothalamus, hippocampus, cingulate
Output: posterior cingulate
What do layers 2 and 3 of the sensory and association cortexes do?
Send info to other cortical areas
What is a callosal connection?
Info from cortex of one hemisphere to the other
Where does layer 6 project?
The thalamus
Where does layer 5 project?
Thalamus and other sub cortical structures (BG, midbrain, brainstem, spinal cord)
What four thalamic nuclei project to the primary sensory cortex?
LGN, MGN, VPL, VPM
Where do modulatory inputs come from?
From the thalamus and brainstem to the cortex
What has the highest density of corticocortical connections?
The association cortex rather than the primary
What is the function of the association cortex?
Integrate different modalities
Mediate internal cognition
Mediate between sensory inputs and appropriate behavioral output
What is the parietal cortex associated with?
Visual attention, localization, spatial relationships, motor programs
What area of the cortex does recognition and object identification?
Temporal cortex (also language)
What does the parietal association cortex do on the non dominant hemisphere?
Attention
Visuospatial localization
Spatial relationships
What does the dominant hemisphere of the parietal association cortex do?
Skilled movements
Right-left orientation
Where is attention best localized to?
The posterior (inferolateral) parietal cortex
In the inter parietal sulcus
What is the stroop test?
Have the name of a color in a specific color
Where is the stroop test localized to?
Posterior parietal cortex
What does damage to the posterior parietal cortex (attention) do?
Spatial neglect (non dominant) Motor apraxia (dominant)
What is spatial neglect?
Failure to acknowledge half the world
Can apply to the world, your body, thoughts and memories
Occurs in about half of right hemisphere strokes
Where is motor apraxia associated with?
Inter parietal sulcus
Inability to perform skilled movements
Sensory and motor systems in tact
What is ideomotor apraxia?
Cannot use tools
May or may not be able to perform action in daily life
Use of hand in place of imaginary tool indicates damage
What is ideational apraxia?
Inability to sequence actions
What is orofacial apraxia?
Inability to make specific facial movements
What area of the temporal lobe is involved in recognition?
Inferior temporal cortex and deeper structures
What area do the temporal lobe does language and social attention?
Superior temporal sulcus
What is important about face neurons?
No grandmother neuron
Represented through population coding
Each neuron responds to a particular feature and together build an image
Body parts and places may have specific regions
What is agnosia?
Deflects In recognition
Inability to recognize or identify objects
What is prosopagnosia and what causes it?
Inability to recognize faces
Caused by bilateral lesion of the inferior temporal cortex
What is visual agnosia caused by?
Damage to unimodal visual cortex
Can’t recognize an object by sight
What is Astereognosia and what is it caused by?
Inability to recognize an object by touch alone
Caused by damage to unimodal somatosensory cortex
What is finger agnosia?
Right- left confusion
Gerstmann syndrome
Damage to angular gyrus of dominant parietal cortex
What does damage to the PFC do?
Impaired restraint Can't plan Disordered thought Perseceration Cannot guide behavior Inappropriate behavior
What is the changes of the cortex over maturation?
Synaptic density
Myelination
Gray matter thickens
What is the gradient of maturation of the PFC?
Posterior to anterior
- Sensorimotor
- Unimodal association areas
- Highly connected PF, posterior parietal is last (attention)
What areas degenerate first?
The ones that matured last