Why is it a two-system model?
dual brain systems provide us with
the flexibility to react instantly (subcortically, unconsciously) or more thoughtfully
(‘consciously’) to environmental threats
Which ‘different’ brain pathways/processes are involved in emotional responsiveness vs conscious experience of fear (emotions)?
- thalamo-amygdala route –> defensive responses
- thalamo-cortico-amygdala route –> FEAR
- -> concsious experience: higher-order cortex important (l&mPFC, insula)
Does LeDoux see the amygdala as the centre of explicit emotional experience?
amygdala is not itself responsible for the experience of fear but can detect & respond to present or imminent threats –> higher-order circuits important for experience
What (implicit) processes does LeDoux think underlie conscious emotional experiences?
-circuits in higher-order association cortex
–> areas:
• Lateral & medial PFC
•Insula
Why is fear not what causes threat responses?
- fear –> due to higher-order association cortex
- threat responses –> not dependent on cortex
Why can people without an amygdala still feel fear?
-since amygdala not itself responsible for fear (but cortex!)
What does the figure mean (PTSD& amygdala activity)?
-PTSD: hyperactive amygdala
–> greater amygdala responsiveness to
negative pictures (vs fixation cross) in
PTSD patients
What could a hyperactive amygdala in PTSD patients imply?
-amygdala hyperactivity:: persistently elevated fear response & hypoactivity in frontal regions suggests a reduced potential for top-down regulation of fear & fear extinction
==> reduced PFC control on sub-cortical ‘survical’
pathway including amygdala
How could conditioned emotion/fear responses be involved in this? How to explain higher amygdala responsiveness to negative stimuli in
anxiety disorder patients? Particular role for conditioned emotional responsiveness
- Fear conditioning: depends on amygdala
- decreased top-down control (PFC)
‘Aversive conditioning network’ including different brain areas/circuits (Holzschneider et al): what are the most important ones?
anterior cinculate cortex (ACC), anterior insula (AI) & amygdala
How does this aversive conditioning network function in patients with anxiety disorders? –> PTSD
- hyperactive amygdala & hypoactivity in the mPFC & ACC
- less active hippocampus
How does this aversive conditioning network function in patients with anxiety disorders? –> OCD
- striatal dysfunction leads via direct & indirect pathways to inefficient thalamic gating –> hyperactivity within the OFC &ACC
- -> amygdala hyperactivation in OCD patients might reflect general emotional hyperarousal rather than OCD-related anxiety
Global workspace theory (LeDoux)
subjective experience emerges through widely distributed reentrant circuitry, with prefrontal areas playing an especially prominent role
Higher-order theory (Le Doux)
subjective experience arises from a more delimited circuitry, especially involving a prefrontal hub, which supports thoughts about lower-order information
