Task 2 - Brain & Emotion Flashcards
Darwin’s view on emotion
- Human emotions are homologises to those of animals
- many emotional expressions in humans are vestigial - Limited set of basic emotions present across all species (anger, fear, surprise, sadness)
—> research in animals to understand human emotions
James-Lange theory of emotion
-Emotions = bodily responses to emotional stimuli
Bodily response —> subjective experience
Theory has remained influential
Main contribution: emphasis on embodiement of emotions
Cannon-bard theory of emotion
Hypothalamus involved in emotional response to stimuli
- responses can be inhibited by neocorticak regions
Papez circuit
- sensory messages (emotional stimuli) arrive at thalamus
—> directed to cortex (stream if thinking) and hypothalamus (stream of feeling)
Cingulate cortex integrates signals from hypothalamus and sensory cortex —> emotional experience
Top-down control:
Cingulate cortex—> hippocampus —> hypothalamus
Klüver-Bucy Syndrome
Removal of temporal cortices in monkeys extinguishes emotional responses to stimuli
—> temporal lobes crucial for emotions
MacLeans limbic system
- broadly supported
Hippocampus seen as core structure of the limbic system
- receives sensory input from outside world + information from internal body state
- integrate external and internal information streams —> emotional experience
The Amygdala
Removal —> Klüver-Bucy syndrome
- key role in processing social signals of emotion (especially threat related, fear), emotional conditioning (fear conditioning & extinction) & emotional memory consolidation
Amygdala & fear conditioning
Fast vs slow response
Two afferent routes mediate conditioning
- Thalamo-amygdala route
—> process crude sensory aspects of incoming stimuli
- early conditioned fear response - Thalamo-cortico-amygdala route
—> more complex analysis of incoming stimuli
-slower conditioned emotional response
PFC
- OFC
- PFC& Amygdala
- PFC &ACC
- PFC & bodily signals
OFC —> learning emotional and motivational value of stimuli
PFC&Amygdala —> learn & represent relationship between primary and secondary reinforcers
PFC & ACC —> send bias signals to other brain regions
-top down control
PFC&Bodily signals —> somatic marker hypothesis (VLPFC)
- Physiological reactions that tag previous emotionally significant events
ACC
- integrates visceral, attentional & emotional information
—> regulation of affect (top-down) - key substrate for conscious emotional experience
Dorsal cognitive subdivision
Ventral affective subdivision —> activated by emotional stimuli
- monitors conflict between internal state and new information that might have affective or ,motivational consequences
Hypothalamus
Rewarding stimuli —> sex, hunger
Single system models
Cannon, Papez, MacLean
Dual system models
Davidson’s valence asymmetry model
-activation/inhibition
Multiple systems models
Darwin
—> different emotions underpinned by separate brain regions
Traditional fear circuit view
Threat—> sensory system —> fear circuit —> fear response (defensive behaviour, physiological responses & conscious experience)
Two system model of fear
Fear= product of cortical cognitive circuits (WM)
Subcortical circuits —> control defensive behaviour & physiological responses (contribute indirectly to conscious experience of fear)
Emotional & non-emotional states of consciousness arise from the same systems
Anxiety —> distant/ abstract threat
BNST = hub for anxiety
—> extended survival circuit
Amygdala = hub of fear circuit (downregulated by MPFC in healthy subjects)
NAcc —> defensive actions
Do responses to threat and subjective fear arise from the same area (Amygdala)?
Why not?
1) subjective fear and anxiety do not correlate well with physiological/behavioural responses
2) patients with amygdala damage still feel fear, panic and pain
3’ threats trigger amygdala activity and physiological responses even if subjects remain unaware
4) blindsight: threat induce pd amygdala activity & defensive behaviour even in absence of conscious awareness
Amygdala —> Responsible for detecting and responding to immediate threats, but not for producing subjective feelings of fear –> It is not innate fear center
Emergence of conscious experience
Subjective feeling of Fear & anxiety underlies same circuits as any other form of conscious experience –> Higher-order cortical regions
- Global workspace theory
- Higher-order theory (prefrontal hub)
—> separate circuits for conscious feeling and response control
–> Amygdala contributes indirectly to subjective feelings –> One interprets the bodily signals and integrates these signals with context information
Classical fear conditioning
Neutral stimulus repeatedly paired with aversive stimulus Which elicits autonomic fear response
- activity in ACC, anterior insula, amygdala —> aversive conditioning network
–> After some time the person habituates and the activity in the amygdala decreases
Extinction of conditioned fear response
Neutral stimulus repeatedly presented without aversive stimulus —> conditioned fear response gradually eliminated
- involves aversive conditioning network
+ prefrontal regions (regulate amygdala fear reaction)
Symptom provocation paradigm
Contrast negative emotional condition with neutral condition
—> hyperactivity of amygdala during symptom provocation
- codes salience/relevance/value
Enhanced activation of fear network:
Insula: subjective feelings & interoceptive awareness
ACC: approach/avoidance, fear learning
PTSD (neuroimaging)
Amgygdala hyperactivity —> elevated fear response
Hypoactivity jn mPFC and ACC —> impaired top-down control
Reduced hippocampal activity —> difficulties in defining safe contexts
Structural changes in hippocampus, amygdala and mPFC
OCD (neuroimaging)
Striatal dysfunction
Hyperactive amygdala & insufficient top-down control
Hyperactive OFC and ACC
