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TASK 2 - THE ANXIOUS BRAIN (LeDoux (TERMINOLOGY (defensive circuits =…
TASK 2 - THE ANXIOUS BRAIN
DALGLEISH
History of affective neuroscience
James-Lange theory
Darwin
Cannon-Bard theory
Papez Circuit
upstream thought stream
downstream feeling stream
MacLean's limbic system
Kluver-Bucy syndrome - lack of temporal lobes elicits lack of emotional reacitivty
MacLeans theory
reptilian brain
old mammalian brain
new mammalian brain
Important areas for emotion
amygdala - social signals of emotion, fear conditioning, memory consolidation
direct thalamo-amygdala route
thalamo-cortico-amygdala pathway
PFC
reward processing (primary and secondary reinforcement)
bodily signals
somatic marker hypothesis (VMPFC)
interoceptive blindness - great difficulty with situations of uncertainty where the subtle emotional values of multiple stimuli need to be processed
top-down regulation
valence-assymetry hypothesis (left-sided PFC approach (positive) goals)
ACC
regulation of affect and other forms of top-down control
point of integration of visceral, attentional and emotional infor
conscious emotion experience
dorsal - cognitive subdivision and ventral/rostral - affective subdivision
hypothalamus - reward system invovling PFC, amygdala and VS
EMOTION SYSTEMS
single system models: Cannon and Bard, Papez, MacLean
dual-system models : Davidson's valence asymmetry model, Rolls dual-system (emotions elicted by positive rewarding , and negative punishing instrumental reinforces)
Multiple-system models: small set of discrete emotions are underpinned by separable neural systems in the brain
LeDoux
TERMINOLOGY
defensive circuits = brain circuits that detect and respond to threats as defensive circuits
defensive behaviors = behaviors that occur in response to threats
defensive physiological adjustments = peripheral changes in physiology that support defensive behaviors as defensive physiological adjustments
fear = feelings that occur when the source of harm, the threat, is either immediate
anxiety = feelings that occur when the source of harm is uncertain or is distal in space or time
FEAR CENTER MODEL
Threat -> Sensory system -> Fear circuit -> Fear responses (defensive behavior and physiological response)
amygdala: bodily reaction to threat and feelings of fear
sensory system - > LA -> CeA (
defensive reactions
like flight and freezing)
sensory system->LA->BA->Striatum NAcc (defensive actions like escape and avoidance)
when uncertain threat: sensory system-> LA -> BA-> BNST -> defensive actions (through NAcc) and reactions
BNST = behavioural inhibition and risk assesment
TWO SYSTEM MODEL
S1 : generating conscious feelings
S2: controlling behavioral and physiological responses to threats
Conscious experience
Global workspace theory
Higher-order theory
Holzschneider
study by Büchel et al.
neutral faces were conditioned with an unpleasantly loud tone
-presentation of the conditioned stimulus evoked brain activity in the
anterior cingulate cortex, the anterior insula, and the amygdala
amygdala activation decreased over time - habituation
Neuroimiging of anxiety disorders
symptom provocation paradigm = contrast a negative emotional condition with a neutral or positive condition to elicit anxiety-specific brain activity + then compared activity in anxiety disorder patients with healthy controls
RESULTS: social anxiety disorder, PTSD, spider phobic individuals:
hyperactivity of the amygdala during symptom provocation that is related to the experienced symptoms of fear
further brain regions like the anterior cingulate cortex and the insula were involved in the development and maintenance of anxiety disorders
PTSD
a) amygdalar hyper-activity = persistently elevated fear response
b) hypoactivity in the medial prefrontal cortex + anterior cingulate cortex = reduced potential for top-down regulation of fear and fear extinction
c) reduced hippocampal activity = difficulties in identifying safe contexts
OCD
cortico-striatal model of OCD: striatal dysfunction -> inefficient thalamic gating -> hyperactivity within the orbitofrontal and anterior cingulate cortex
a) Orbitofrontal hyperactivity occurrence of intrusive thoughts
b) hyperactivity within the anterior cingulate cortex -> unspecific anxiety arising from these thoughts
c) compulsions -> performed to compensatory activate the striatum, achieve thalamic gating -> neutralize intrusive thoughts and anxiety