Question

Discuss the neural basis of auditory Pavlovian fear conditioning. In your answer make reference to the following: Describe the major sensory inputs to the lateral amygdala and the major output projections of the central nucleus that control different components of the fear response (e.g. freezing vs. autonomic fear CRs). Describe the evidence that indicates that the lateral amygdala is a site of CS-US integration in the fear memory system and neurophysiological evidence that indicates that that the formation of auditory fear memories involves Hebbian alterations in the firing properties of lateral amygdala neurons (Hint: think “weak” vs. “strong”). Describe how fear memories are acquired and consolidated at the molecular level, including a discussion of evidence gathered from pharmacological manipulations that suggests that different molecules involved in E-LTP & L-LTP contribute to short- and long-term formation of memories

Answer 1

Pavlovian fear conditioning ​​​​​​ is a form of associative memory formation where a conditioned stimulus(CS) paired with unconditioned stimulus(US) that elicits a fear unconditioned response (UR).

Fear reaction starts in the brain and spreads through the body to make adjustments for the best defense.The fear response starts in the region of brain called Amygdala.

AMYGDALA:- It is an almond-shaped section of nervous tissue located in the temporal (side) lobe of brain. It is responsible for the perception of emotions such as anger, fear and sadness.size is positively correlated with aggressive behaviour across species. It plays major role in formation and storage of memories associated with emotional events.

It is composed of multiple sub- nuclei including lateral nucleus, basal nucleus and the central nucleus. The lateral nucleus is the main sensory input to the amygdala. The central nucleus is the main output from amygdala for the physiological expression of emotions.

Scientists conducted an experiment on mice to learn fear conditioning. It is a type of associative learning task in which mice learn to associate a particular neutral conditional stimulus (CS) usually a tone, with an aversive unconditioned stimulus (US) usually a electrical foot shock and show a conditional response (CR) often as freezing. After repeated pairings of CS and US, animal learns to fear both the tone and foot shock. After that a very stable and long-lasting behavioural change is produced which is useful for neuro behavioural, genetic and pharmacological studies. In trace FC the CS and US are separated by certain time interval. It has been shown that the front temporal amygdala has an important role in both acquisition and expression of conditional fear and that the hippocampus is necessary for contextual and trace FC.

Memory is the reactivation of specific group of neurons, formed from persistent changes in the strength of connections between neurons. Lasting increases and decreases in synaptic strength are called long term potentiation (LTP).