The amygdala and emotion

Question 1

amygdala role in emotions

Answer 1

• Robust evident that the amygdala is related to emotions
• Injuries in the amygdala is associated with diminished emotional responses (not total loss)
• Studies in humans have confirmed the key role of the amygdala in fear conditioning
• Within the fear circuits the amygdala:
• Detects the threat on an unconscious level
• Regulates behavioural and physiological responses
• Send signals to the cognitive systems which in turn give rise to the conscious feeling of fear

Question 2

the low and high roads to fear in the amygdala

Answer 2

• Ledoux (1996)- identified 2 different pathways that lead to the amygdala: a ‘quick and dirty’ low road and a ‘slow but accurate’ high road
• The low road does not involve cortical processing and activates the amygdala in a 12 Ms time-frame
• This dual process enables us to react before we (consciously) fear

Question 3

The amygdala and the HPA axis

Answer 3

• In response to detected threat, the amygdala stimulates the HPA axis thru indirect projections to the hypothalamus, resulting in a release of CRF, which stimulates the anterior pituitary to release ACTH into the bloodstream
• In turn stimulates the secretion of cortisol in the adrenal gland, causing blood levels of cortisol to rise

cortisol is the stress hormone playing a important role in cognition and emotional state

Question 4

survival circuits (vs subjective feelings)

Answer 4

• Ledoux (2012) proposed a reconceptualization and re-named the circuits as the ‘survival circitis’
• The proposed reconceptualization recognises the amydala importance in triggering physiological responses to threat, but asserts that it is less important to subjective feelings
• An evidence is that direct electrical stimulation of the amydala reliably elicits physiological responses, but subjects do not report feelings (Inman et al., 2020)
• Moreover, patients with amygdala lesions can consciously report emotional experiences, including fear (Anderson and Phelps)

Question 5

the amygdala and mental disorders

Answer 5

• Anxiety disorders are associated with amygdala hyper-reactivity to threatening and neutral stimuli (Janack & Tye, 2015)
• This applies to panic disorder, social phobias, and, to a lesser extent, PTSD and GAD
• Increased amygdala activity leads to hypothalamo-piturity axis activation and subsequent increase in hormone levels
• Similar amygdala hyperactivity as well as reduced PFC activity is also observed in depressive disorders.

Question 6

The amygdala in reward processing

Answer 6

• Amygdala lesions impair reward-based behaviour (Janak and Tye, 2015), particularly in the ability to respond to cues in the face of changing reward value
• Evidence has shown that the amygdala encode stimulus valence in addition to salience (Sangha et al., 2013):
• • some neurons respond only to a fear cue while other neurons respons only to a reward cue
• Some other neurons respond to both fear and reward cue, and proportionately to ANS activation

Question 7

OBFC

Answer 7

• OBFC- connected reciprocally with the amydgdala, forming a tightly linked circuit
• It has a polymodal processing capacity, receiving multi-modaality inputs both directly from neocortical sensory areas and indirectly via the amygdala
• It is thought to act as an integrator of the inner and outer worlds, and is responsible for out ‘gut reactions’ to people and events
• Recent studies found that the OBFC represents reward value, and its lesion impairs decision making in situation of cessation of previously available reward.

Question 8

Pessoa & McMenamin (2017)

Answer 8

During sustained threat, the amygdala become more central to communication and play an important role in determining the strength of the anxious state. For example, if threat is stronger and more imminent, an apprehension state can result that focuses processing resources on the threat, leaving fewer resources for threat-unrelated processing.