Neuroscience Limbic System Russell T. Matthews Flashcards
What did Papez hypothesize about the limbic system?
That it is involved with emotions, the Papez circuit
What is the Papez circuit? (Four items)
- Hippcampus connected to mammilary bodies
- Mammilary bodies to the anterior of the thalamus
- Anterior nuclesu to the cingulate cortex
- Cingulate cortex back to the hippocampus
T or F: The amygdala is part of the Papez circuit.
FALSE. Kluver-Bucy showed that all emotional symptoms could be recapitulated by removing/damaging the amygdala (monkey experiment)
What are the areas of the limbic system currently thought to be active in emotional processing?
- Amygdala
- Anterior and mid-cingulate cortex
- Mediodorsal nucleus of the thalamus
- Prefrontal cortex
What is the key function of the Anterior Cingulate Cortex (ACC)?
To store emotional/valenced information and recode the amygdala
**regulates ANS
What is the key function of the Mid-Cingulate Cortex (MCC)?
Select responses (mental or motor), predict outcomes, resolve ambiguity, improvise new behavior for new problems **resolves conflict, regulates skeletomotor output
What is the key function of the amygdala?
Invests sensory experience with emotional significance (valence), most prominently involved in fear
What is the key function of the hypothalamus?
Autonomic, hormonal control
What is the key function of the periaqueductal gray?
Coordinate behaviors, autonomic/skeletal
What is the key function of the locus coeruleus?
Coordinates responses and enhances storage of emotional memories
What is the key function of the dorsal raphe nucleus?
Regulates mood
What are secondary emotions?
Conscious emotions, involve conscious processing
What is the effect of Urbach-Wiethe disease?
Calcification of the amygdala
What was special about patient S.M.?
She has no fear response, but her motor, sensory system, intelligence level and function, and memory were intact. She had loss of her amygdalas bilaterally due to Urbach-Wiethe disease, a genetic disorder.
The amygdala receives direct input from the:
thalamus
Memory is directly enhanced in the presence of:
norepinephrine
What specific locations in the brain mediate the fight or flight response?
Amygdala to the periaqueductal gray and locus coeruleus (and connections from the LC to the PAG)
What is/where is the periaqueductal gray?
It is part of the limbic system, surrounds the cerebral aqueduct in the midbrain.
T or F: PAG has no memory. It is controlled by higher brain regions.
True
What are the behaviors stimulated by the PAG?
Could be anything in the F or F response, or quiescent/bradychardic response. Depends on the area of the PAG being stimulated.
A stroke or tumor to the hypothalamus/PAG can produce:
Sham rage
Activation of the __1__ causes quiet resting behavior, while activation of the __2__ causes affective defensive behaviors.
- Ventromedial Hypothalamus (VMH)
2. Lateral Hypothalamus (LH)
PAG acts through other circuits to produce what kind of response, which heightens the feeling of emotions?
ANS
What region of the cingulate cortex acts through the ANS?
ACC
Through what projections does the ACC act through the ANS?
- NST, nucleus of the solitary tract
2. DMX, dorsal motor nucleus of the vagus
What area of the brain is particularly vulnerable to emotional diseases such as depression?
Perigenual region of the corpus collosum
What parts of the cingulate cortex are most involved in processing emotion?
The ACC, and the anterior part of the MCC (NOT the posterior regions)
PET studies show activation in the ACC when remembering what kinds of events?
Sad events
Electrical stimulation of the MCC produces what?
Complex motor outputs, such as emotionally valenced motor behaviors, ie kissing.
Where does emotional facial expression and interpretation occur in the brain?
ACC (facial region)
Provide the summary of the fear response from stimulus to facial response:
- Sensory stimulus activates amygdala
- Amygdal activates upstream (ACC) and downstream (PAG)
- ACC further activates PAG, and activates facial area at ACC/MCC border
- Facial area activates facial nucleus ad facial expression
Storage of emotionally valenced memories in the amygdala and ACC depends on what critical item?
Norepi released from the LC
LC is critical for what responses?
F-or-F
Where is the LC?
Pons, regulates HPA axis
Summarize the 4 points at which the LC intercedes in the limbic system to coordinate motor outputs.
- Nucleus of the solitary tract (NST/paraventricular nucleus (PVT) in the thalamus mediate heart rate responses from the ACC/Central amygdala
- PAG: NE selects F-F
- PVN (paraventricular nucleus in the hypothalamus) drives HPA axis: NE, ACTH, Cortisol
- Enhances amygdala processing and memory
What behavior disorders are associated with the limbic system?
Conduct disorders
Criminal psychopathy
Sociopathies
What mood disorders are associated with the limbic system?
PTSD Anxiety Depression Schizophrenia (Addiction) **Most prevalent are A&D
Why does the limbic system play a secondary role in nearly all neuropsychiatric disorders?
Bc it is an integration point for all the biogenic amines (5HT, dopamine, serotonin, NE)
What are some structural and functional evidences of mood disorders in the limbic system (3)?
- Increased amygdala size in adolescents with high anxiety
- Decreased ACC size in patients with MDD
- Reduced glucose metabolism in ACC in MDD
Where is the specific area of connectivity between the ACC and the amygdala, where glucose metabolism is reduced in MDD?
genu of the corpus callosum
The dorsal Raphe nuclei are located where in the brain?
In the midbrain, PAG on either side laterally
What is the major source of 5HT in the brain?
DRN
What are the first-line strategies for treating mood disorders such as MDD?
Modulation of NE and 5HT
