Trace Fear Conditioning in Mice

Podsumowanie

In the following experiment we describe a protocol for trace fear conditioning in mice. This type of associative memory includes a trace period that separates the neutral stimulus and the unconditioned stimulus.

Streszczenie

In this experiment we present a technique to measure learning and memory. In the trace fear conditioning protocol presented here there are five pairings between a neutral stimulus and an unconditioned stimulus. There is a 20 sec trace period that separates each conditioning trial. On the following day freezing is measured during presentation of the conditioned stimulus (CS) and trace period. On the third day there is an 8 min test to measure contextual memory. The representative results are from mice that were presented with the aversive unconditioned stimulus (shock) compared to mice that received the tone presentations without the unconditioned stimulus. Trace fear conditioning has been successfully used to detect subtle learning and memory deficits and enhancements in mice that are not found with other fear conditioning methods. This type of fear conditioning is believed to be dependent upon connections between the medial prefrontal cortex and the hippocampus. One current controversy is whether this method is believed to be amygdala-independent. Therefore, other fear conditioning testing is needed to examine amygdala-dependent learning and memory effects, such as through the delay fear conditioning.

Wprowadzenie

In fear conditioning a neutral stimulus (NS) is paired with an aversive unconditioned stimulus (US). The NS is normally a tone and becomes a conditioned stimulus (CS) through repeated pairings with the US. The CS can then elicit a conditioned response (CR), such as freezing, in the absence of the aversive US. A commonly used fear conditioning protocol is delay conditioning. In this protocol the onset of the NS and the US is contiguous or with some overlap in stimulus presentation. Even though delay fear conditioning is one of the most commonly used types of temporal associative conditioning, there are several other types of associative conditioning temporal arrangemen....

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Protokół

The mice used in the following experiment were generated and housed at Baylor University at an ambient temperature of 22 °C, with a 14 hr light and 10 hr dark (20:00 to 6:00 hr) diurnal cycle. The mice were given ad libitum access to food and water. All procedures to the mice were in compliance with the National Institutes of Health Guidelines for the Care and Use of Laboratory Animals and the animal protocol was approved by Baylor University Animal Care and Use Committee.

Overview

The trace conditioned fear task is based on procedures described by Wiltgen and colleagues⁹.

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Wyniki

For the representative results we present data from control C57BL/6J adult mice that received the neutral stimulus pairings with the unconditioned stimulus (shock condition) compared to mice that received the neutral stimulus but did not receive the unconditioned stimulus (no shock condition). It is important to run this condition when first setting up this behavioral test to determine whether the protocol has been performed correctly.

The data in Figure 1 represent the traini.......

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Dyskusje

There have been several studies that have elucidated the neural circuitry that underlies trace fear conditioning. Trace fear conditioning is believed to involve the CA1 of the hippocampus^12-14. There is also evidence that the medial prefrontal cortex (mPFC) plays a large role in trace eye-blink conditioning¹⁵, and the mPFC has been found to be involved in trace fear conditioning. One study found that mPFC neurons provide sustained activity during the trace period, thus providing a structure that can.......

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Materiały

Name	Company	Catalog Number	Comments
FreezeFrame	Coulbourn
30% Isopropanol			Purchase 90% isopropanol and dilute it down to 30%
70% Ethanol
Amp-meter	Med-Associates	ENV-420	Windows XP, Vista, and 7 Compatible (32-bit only)
Digital Sound Level Meter		33-2055
Vanilla Extract	McCormick Pure Vanilla Extract
Sticky Notes	Post-it		3 in x 3 in