Neural Mechanisms of Fear Conditioning

Question 1

Fear conditioning

Answer 1

The establishment of fear in response to a previously neutral stimulus (the conditional stimulus) by presenting it, usually several times, before the delivery of an aversive stimulus (the unconditional stimulus).

Question 2

Prefrontal cortex

Answer 2

Is thought to act on the lateral nucleus of the amygdala to suppress conditioned fear.

Question 3

Contextual fear conditioning

Answer 3

The process by which benign(goede) contexts come to elicit fear through their association with fear-inducing stimuli

Question 4

Hippocampus

Answer 4

• Plays a key role in memory for spatial(ruimtelijk) location.
• Bilateral hippocampal lesions block the development of a fear response to the context without blocking the development of a fear response to the conditional stimulus (e.g., a tone).
• Is thought to interact with the lateral nucleus of the amygdala to learn about the context of fear-related events.

Question 5

Circuit of brain - mediate fear conditioning to auditory conditional stimuli

Answer 5

Sound signals from the medial geniculate nucleus of the thalamus reach the amygdala directly, or indirectly via the auditory cortex. The amygdala assesses the emotional significance of the sound on the basis of previous encounters with it, and then the amygdala activates the appropriate response circuits—for example, behavioral circuits in the periaqueductal gray and sympathetic circuits in the hypothalamus.

Question 6

The amygdala

Answer 6

• Receives input from all sensory systems, and it is believed to be the structure in which the emotional significance(betekenis) of sensory signals is learned and retained.
• Several pathways carry signals from the amygdala to brain-stem structures that control the various emotional responses.
• -> Pathway periaqueductal gray of the midbrain(outputs from the central nucleus of the amygdala) elicits appropriate defensive responses
• -> Pathway lateral hypothalamus elicits appropriate sympathetic responses.

Question 7

LeDoux and colleagues - auditory fear conditioning

Answer 7

• For the auditory fear conditioning to occur, it is necessary for signals elicited by the tone to reach the medial geniculate nucleus but not the auditory cortex.
• The pathway from the medial geniculate nucleus to the amygdala plays a key role in fear conditioning.
• Both pathways to amygdala capable of mediating fear conditioning to simple sounds; if only one is destroyed, conditioning progresses normally. However, only the cortical route is capable of mediating fear conditioning to complex sounds.

Question 8

Lateral nucleus of the amygdala

Answer 8

Is critically involved in the acquisition, storage, and expression of conditioned fear

Question 9

Name 2 ways contextual fear conditioning has been produced in the laboratory

Answer 9

1. Produced by the conventional fear-conditioning procedure.
   Rat repeatedly receives electric shock following a conditional stimulus(tone) –> rat will become fearful of the conditional context (the test chamber) as well as the tone.
2. Delivering aversive stimuli in a particular context without another conditional stimulus.
   Rat receives shocks in a distinctive test chamber –> rat will become fearful of that chamber.