Lecture 07 - Limbic System

Question 1

Limbic system

Answer 1

feeling and reacting brain

• physiological arousal (autonomics), expressive behaviors (somatomotor and autonomics) and conscious experience (happy vs. sad)
• parts of cerebral cortex (orbital and medial prefrontal cortex, anterior cingulate cortex, amygdala)
• parts of hypothalamus (paraventricular nucleus)
• Ventral striatum/BG (ventral pallidum, N. accumbens)
• MD nucleus of thalamus

Question 2

Olfaction

Answer 2

hooks up with emotional limbic system (amygdala/orbitofrontal cortex and hippocampus)
-ties in with memories and feelings evoked

Question 3

Components of emotional expression

Answer 3

1. autonomic/visceral response (HR, BP)
2. somatomotor response (facial expressions)
3. actual internal “feeling”

Question 4

somatomotor output

Answer 4

• voluntary facial contractions
• body configuration/muscle contraction
• innervated by neurons NOT in primary and 2ndary motor cortical areas
• cells in layer 5 of cingulate cortex also has motor inputs to LMNs innervating lower face
• UMN lesion = can’t voluntarily smile with whole face, but when laughing at something funny, can fully smile
• emotional cortical lesion = can’t smile from emotion, but can when non-emotional

Question 5

Autonomic output

Answer 5

Hypothalamus and amygdala - also have reciprocal connections

• both act on autonomic centers in brain that act on symp or parasymp, or direct to autonomic neurons
• maintain homeostasis
• hypothalamic outputs activate autonomics thru brain or direct, or via pituitary (HPA axis)
• PVN acts primarily via dorsal longitudinal fasciculus (DLF) and medial forebrain bundle (MFB)
• DLF is major descending pathway

Question 6

Horner’s syndrome

Answer 6

issue with descending pathway from hypothalamus to sympathetics (dorsolateral brainstem)

• dama to PICA
• droopy eyelid, constricted pupil, no sweat, hyperemia

Question 7

Amygdala

Answer 7

structure that exists in every vertebrate

• detect changes in the environment (prepare and respond to threat)
• set of nuclei
• basolateral considered “amygdala proper”
• learning when fear response and neutral stimulus presented together –> arrive together and converge on same amygdala cells –> gradually tone alone triggers
• vmPFC controls amygdala via feedback

Question 8

Cingulate cortex

Answer 8

• may store memories of emotional events (emotional awareness)
• may generate relevant skeletomotor behavioral/emotional activity

Question 9

Basal Ganglia

Answer 9

emotion part = reward and decision making (limbic loop)

-vmPFC driven