Limbic System Flashcards
1
Q
Le Grande Lobe Limbique
A
- Described by Broca
- Cortical areas forming a rim around the diencephalon on the medial surface of the brain
- Cingulate cotex, parahippocampal gyrus, olfactory cortex
- Originally though to have primary role in olfaction
2
Q
Papez Circuit
A
- James Papez hypothesized the limbic system is involved in emotions
- Components: Hippocampus connected to mammilary bodies (hypothalamus), mammilary bodies connected to the anterior nucleus of the thalamus, anterior nucleus connected to the cingulate cortex, cingulate cortex back to the hypothalamus
- KEY missing part: amygdala
3
Q
Klucy-Buver Experiment
A
- Removal of temporal lobes of aggressive monkey
- Became docile, over ate, ate inappropriate things, hyperoral, hypersexual
4
Q
Modern limbic system primary components
A
-Amygdala, anterior and mid-cingulate cortex, mediodorsal nucleus of thalamus, prefrontal cortex
5
Q
Anterior cingulate cortex
A
- Store emotional/valenced information and recode the amygdala
- Involved in AFFECT
- Stores long-term emotional memory
- Operates through ANS projections to the nucleus of the solitary tract and dorsal motor nucleus of vagus
6
Q
Mid cingulate cortex
A
- Select responses (mental or motor), predict outcomes and resolve ambiguity, improvise new behaviors for new problems
- Involved in motivated behavior and response selection
- Anterior part activated during fear
- Operates through spinal projections to the skeletomotor system
- Projections to the striatum, red nucleus, pontine nuclei, and CN nuclei for somatomotor driving of Alpha motor neurons
7
Q
Amygdala
A
-Invests sensory experience with emotional significance (valence), most prominently in fear
8
Q
Hypothalamus
A
-Autonomic/hormonal control
9
Q
Periaqueductal gray
A
- Coordinate behaviors, autonomic/skeletal
- Surrounds aqueduct in the midbrain between 3rd and 4th ventricle
- Stimulating different parts produce different classes of behavior
- Ventral area: rest and digest, dorsal: fight or flight
- Has none of its own memory
10
Q
Autonomic nervous system
A
-Skeletal motor output and memory enhancement
11
Q
Locus Coeruleus
A
- Coordinates responses and enhances storage of emotional memories, helps to remember responses
- Critical for fight or flight response
- Located in pons
- Extensive projections throughout the cortex, especially the limbic parts
- Driven by input from the amygdala and limbic cortex
- Releases norepi that is critical for storage of emotionally valenced memories
12
Q
Dorsal Raphe Nucleus
A
-Helps to regulate mood, produces serotonin
13
Q
Two types of emotion
A
- Primary: fear, surprise. Reflexive emotions linked with autonomic reflexes (amygdala, hypothalamus, PAG)
- Secondary: conscious emotions (cortical limbic structures and hippocampus)
14
Q
Basal-lateral nucleus of amygdala
A
- Input: thalamus, sensory, entorihinal, and association cortex
- Output: cortex and striatum
15
Q
Central nucleus of amygdala
A
- Input: brainstem, sensory and prefrontal cortex
- Output: brainstem and hypothalamus
- Connects to basal lateral to mediate fear response
16
Q
Urbach-Weithe Disease
A
- Loss of amygdalas due to calcification (hippocampus left intact)
- Example patient SM could not recognize fear
17
Q
Inputs to the amygdala
A
- MGN
- Auditory cortex
- Thalamus
- Receives primary and sensory input from all modalities
- Direct input from thalamus critical to the role of the amygdala in fear response
18
Q
Primary emotion (fear) response steps
A
- Fear evoking stimulus (visual)
- Stimulus perceived
- Input goes directly from LGN to the amygdala, activating fear response (activates cortex and output pathways)
- Expression of fear somatically and viscerally through ANS activation
- Memory of event encoded in the amygdala and cortex
- Memory enhanced by presence of norepi for the LC
19
Q
Sham rage
A
- Lesion to the hypothalamus/PAG can produce a rage without external control (primary emotion)
- Activation of the lateral hypothalamus is the cause
- So losing the descending control to PAG can be dangerous
20
Q
PAG projections
A
-Regulates projections to the nucleus of the solitary tract, dorsal motor nucleus of vagus, intermediolateral nucleus–activates ANS during emotional events
21
Q
HPAA Axis
A
- Amygdala and limbic cortex and NE from LC cause paraventricular hypothalamic nucleus (PVN) to secrete cortisol releasing hormone (CRH) into portal veins.
- CRH evokes release of ACTH from pituitary, then evokes release of cortisol from adrenal cortex
22
Q
Effects of the release of cortisol by adrenal cortex
A
- Binds to glucocorticoid receptors
- Increases glucose levels and metabolism
- Increases AA metabolism
- Increases fat breakdown
- Increases memory (amyg, insula, acc)
23
Q
Reciprocal projections from amygdala to ACC
A
-Helps form the conclusion that the ACC is mainly involved in emotion and may be vulnerable to emotional diseases
24
Q
Different regions of cingulate activation with memory of emotional events
A
- Fear: anterior MCC
- Sadness: ventral ACC
- Happiness: rostral ACC
25
Electrical stimulation of MCC results
- Complex motor outputs that are emotionally relevant
| - Ex: lip puckering, finger kneading
26
Site of emotional facial awareness and expression
- Anterior cingulate cortex, called the facial region
- Projects to the facial motor nucleus
- Allows us to read each others emotions, also explains why we "wear our emotions on our sleeves"
27
Points at which the LC intercedes in limbic systems to coordinate motor outputs
- NTS/paraventricular nucleus in the thalamus mediates heart responses from ACC/central amyg
- PAG: NE selects fight or flight
- PVN drives HPA axis: NE, ACTH, Cortisol
- Enhances amygdala processing and memory
28
Disorders of the limbic system
- Conduct disorders, sociopathies, mood disorders, neuropsychiatric disorders
- Most prevent are depression and anxiety
29
Evidence of limbic involvement in depression
- Increased amygdala volume in depressed patients
- Reduced glucose metabolism in ACC in major depression
- Decreased ACC volume in patients with major depression
30
Depression and 5HT in limbic system
- Serotonin produced in raphe nucleus, near PAG
- 5HT is an important modulator of mood through limbic pathways
- Determines tonic activity of the system
31
Deep brain stimulation
- Targets the ACC
- Can be used to treat depression
- Long lasting effects
