17.3 Neural Mechanisms of Fear Conditioning

Question 1

What is Fear conditioning

Answer 1

the establishment of fear in response to a previously neutral (conditional) stimulus by presenting it prior to delivering an aversive stimulus (the unconditional)

Question 2

Explain the standard fear conditioning experiment

Answer 2

rat hears a tone (conditional), followed by a mild electric shock (unconditional)

• after several pairings, the rat response with
  1. defensive behaviours
  2. sympathetic nervous system responses

Question 3

How did Ledoux et al begin their search for the neural mechanisms of auditory fear conditioning

Answer 3

made lesions in the auditory pathways of rats
- bilateral lesions to the medial geniculate nucleus (auditory relay nucleus of the thalamus) blocked fear conditioning, but bilateral lesions to the auditory cortex did not

Question 4

what did the fact that bilateral lesions to the medial geniculate nucleus (auditory relay nucleus of the thalamus) blocked fear conditioning, but bilateral lesions to the auditory cortex did not show? (2)

Answer 4

1. for aud. fear conditioning to occur, it is necessary for signals elicited by the tone to reach the MGN but not the aud cortex
2. a pathway from the MGN to a structure other than the aud cortex plays a role in fear conditioning

Question 5

what was a the structure that the Medial geniculate nucleus project to that allows for auditory fear conditioning?

Answer 5

MGN to the amygdala

Question 6

what effects do lesions to the amygdala have on fear conditioning

Answer 6

they block aud fear conditoning

Question 7

from where does the amygdala receive Input (sensory)

Answer 7

all the sensory systems

Question 8

what do we believe is the amygdala primary role in emotional processing?

Answer 8

structure in which emotional significance of sensory signals is learned and retained

Question 9

How does the amygdala play a role in emotional responses?

Answer 9

several pathways from the amygdala to the brain stem structures that control the various responses exist

Question 10

what is an example of a pathway from the amygdala to the brain stem structures that control the various emotional responses ? (2)

Answer 10

1. Amygdala to periaqueducttal gray of the midbrain elicits appropriate defensive responses
2. amygdala to the lateral hypthal elicits appropriate sympathetic responses

Question 11

what are the two pathways sound signals take to the amygdala

Answer 11

1. directly from the medial geniculate nucleus of the thalamus (directly )
2. indirectly, from the auditory cortex

Question 12

what does the amygdala do with auditory information from the two pathways

Answer 12

assesses emotional significance off the sound of the basis of previous encounters with it, then activates the appropriate response circuits
- example, behavioural circuits n the periaqueductal gray, sympathetic circuits in the hypthal

Question 13

what is contextual fear conditioning

Answer 13

the process by which benign contexts come to elicits fear through their association with fear inducing stimuli

Question 14

what are the two ways contextual fear conditioning has been elicited in the lad

Answer 14

1. produced by conventional fear conditioning procedure

2. produced by delivering aversive stimuli n a particular context in the absence of any other conditional stimulus

Question 15

why is it reasonable to expect that the hippocampus is involved in contextual fear conditioning

Answer 15

bc it plays such a major role in memory for spacial location

Question 16

what confirmed the hippocampus’s role in contextual fear conditioning

Answer 16

bilateral hippocampal lesions block toe development of a fear response to the context without blocking the development of a fear response to the explicit conditional stimulus

Question 17

what is a more accurate description of the amygdala

Answer 17

the amygdala complex, bc it is a cluster of a dozen nuclei with her own sub nuclei, which are each structural distinct with different connections, and have different functions

Question 18

what is the role of the lateral nucleus of the amygdala

Answer 18

it is the structure that is critically involved n the acquisition, storage and expression of conditioned fear

Question 19

what 2 major structures project to the lateral nucleus of the amygdala, and why is this relevant

Answer 19

1. PFC - acts on the lateral nucleus of the amygdala to suppress conditioned fear
2. hippo - interacts with that part of the amygdala to mediate learning about the contest of fear related events

Question 20

how is the amygdala thought to control defensive behavioural outputs?

Answer 20

through its central nucleus!