Neuroscience of fear

What are fear responses?

Behavioural: movement appropriate to situation (fight/flight)

Autonomic: blood vessels constrict/dilate, heart rate changes to enable behavioural response

Hormonal: hormones produced to reinforce the autonomic response (adrenalin)

How is the amygdala used in fear?

Single neurons in lateral nucleus of amygdala increase their firing rate to conditioned stimuli following fear training

How is the amygdala activated in humans?

Left amygdala activated in response to CS+ following instructions that CS+ will be paired with a shock - even when no shock is given

Normal conditioned fear induces bilateral activation

How can extinction reduce fear?

New association is learned between CS & lack of shock/fear

If new learning is blocked in amygdala, rats don’t show extinction

Electrical stimulation of vmPFC can speed up extinction

How can cognitive regulation reduce conditioned fear?

Decreases activation in amygdala: increased activation in prefrontal cortex - same mechanisms that control extinction

What is reconsolidation?

If memories are recalled they become sensitive to change & must be reconsolidated

How can reconsolidation change fear response?

LTP required - can be blocked by blocking protein synthesis

What did Nader et al (2000) find?

Memories were erased by stopping reconsolidation