9/21 Emotions - Glendinning Flashcards
basal forebrain structures
nucleus basalis of Meynert:
- contains cholinergic neurons that project to entire cortex
- roles in attention, memory, learning
septal nuclei:
- “pleasure center”
- anterior to anterior commisure
nucleus of diagonal band: connects nucleus basalis of Meynert and septal nuclei
nucleus accumbens
thalamic nuclei
- n. accumbens: component of basal ganglia “limbic loop”
- _anterior nucleus of thalamu_s: linked to learning/memory
- dorsomedial nucleus of thalamus: linked to emotions
temporal structures
(centered around hippocampal formation)
hippocampus
amygdala
- anterior to hippocampus in temporal lobe
- almond-shaped “corticoid area” (where cortex merges with nuclei)
parahippocampal gyrus
uncus
fornix: main output of hippocampus → projects to mammillary bodies, spetal nuclei, anterior thalamic nucleus
emotions
help humans react, communicate, focus attn, learn from experience
- trigger autonomic and motor responses
- fight/flight
- freezing
- focus our attention
- elicit emotional expression
role of hypothalamus in emotional expression
“angry cat” experiments demonstrate that emotional expression can be driven by hypothalamus in isolation
- made cut through brain that did/did not include the hypothalamus
- only cuts that left hypothalamus-midbrain connection intact showed “sham rage”
emotional expression
occurs through limbic system outputs to hypothalamus and brainstem reticular formation
- motor circuits tap into somatic and autonomic systems to produce:
- laughing, crying, gagging, chewing, facial exp, vomiting
mesencephalic/rostral pontine reticular formation: modulates forebrain activity
caudal pontine and medullary reticular formation: premotor coordination of lower somatic and visceral motor neuronal pools
example of person displaying “contradictory” motor function?
- voluntary vs involuntary mismatch?
how does it happen
yes!
ex. corticobulbar lesion
- asked to smile → voluntary facial paresis
- made to smile via emotion → involuntary smile response (full)
opposite can also happen (facial muscles intact for voluntary activation, NOT for emotional)
how?
voluntary facial paresis interrupts pyramidal smile
- mediated by descending pyramidal and extrapyramidal projections from motor cortex/brainstem
emotional facial paresis interrupts “Duchenne smile”
- mediated by descenting extrapyramidal projections from medial forebrain/hypothalamus
both systems activate motor pools in facial nucleus to attempt to elicit smile
amygdala
emotional center
- assigns value to stimuli (good or bad?)
- enables us to choose appropriate rxn to conditions
- ex. get a reward, avoid something negative
- esp activated when viewing an untrustworthy face
comprise 12 nuclei in 3 groups
amygdala nuclear groups
- MEDIAL nuclei
* olfactory and autonomic functions - BASOLATERAL nuclei
* direct sensory input from thalamus and sensory cortices - CENTRAL NUCLEI
* output nuclei → project to hypothal and brainstem
amygdala pathway
amygdala receives stimulus, then…
projects DOWNWARD (from central nucleus) TO…
- hypothalamus → endocrine responses in bloodstream
- brainstem →
- signals to muscles in face/limbs
- autonomic signals
- signals to nt nuclei
projects UPWARD (from basal nucleus) TO…
- basal forebrain → attention
- frontal association cortex → behavior
summary:
- upper connections: behavioral responses, focusing attn
- lower connections: visceral and autonomic responses (incl arousal)
short and long pathways from amygdala
sensory input FROM thalamus
also sensory input from olfactory (direct or indirect from piriform cortex)
bidirectional connections TO:
- basal forebrain (short)
- thalamus (short)
- hypothalamus (short): emotional changing of memories
- brainstem (short)
- cortex: temporal and frontal association cortex and frontal limbic cortex → deciding behaviors
also a long set of pathways that wraps around to get to basal thalamis/hypothalamic areas (stria terminalis)
emotional brain
enables associative learning between sensory inputs and corresponding feelings/emotions
fear conditioning in amygdala
experiments pair innocuous tones with painful stimulus
- leads to fear of the tone in animals → freezing
NMDA input is important
Kluver Bucy Syndrome
bilateral damage to temporal lobes → loss of amygdala/fx
could be due to…
- herpes simplex encephalitis
- bilat temp lobe surgery
- CNS degen disorders: Alzheimer’s, Pick’s
- lose emotional responses to sensory stimuli
- fearlessness
- loss of rage/aggression, esp towrads humans
- overattn to sensory stimuli (oral examination)
- hyperphagia (excessive eating)
- hyperactivity
- hypersexuality
fear-learning in PTSD
association of sensory stimuli with fear appears to play a role in PTSD
- trauma/pain sensation is enhanced by simultaneous input of norepi from locus ceruleus
in fear-cond trials, people with PTSD show:
1. hyperactivation of amygdala
2. hypoactivation of prefrontal cortex (vPFC)
amygdala and motivation
amygdala also generates visceral and behavioral responses to positive stimuli as well as negative stimuli →→→ involved in generating motivations
repeating things that are pleasurable activates a “habit forming” pathway involving basal ganglia
- ventral basal ganglia: nucleus accumbens (part of reward pathway)
pathway for emotional reinforcement
DA neurons fine when an experience is rewarding → reinforces direct loop
ventral tegmentum nucleus releases dopamine → nucleus accumbens/orbitofrontal cortex when experiencing things we like
- monetary reward
- pleasant music
- attractive facial expressions
- seeing good food
*link to addiction: most abused drugs have a link to dopamine → prolong action of dopamine in n. accumbens
