The overall goal of the following experiment is to prevent the recovery of fear memory by introducing extinction training during the reconsolidation window. This is achieved by using classical fear conditioning to train participants to associate an innocuous stimulus with an aversive outcome while physiological measures are recorded as an index of fear arousal. As a second step subjects return a day later and receive extinction training during the reconsolidation window opening, using a reminder queue of the CS plus outside the same reconsolidation window, or simply undergo standard extinction training without reconsolidation.
Next, participants should return to the lab the following day to be tested for fear recovery results show that undergoing extinction training within the reconsolidation window leads to significantly less fear recovery when compared to those receiving extinction training at other times. The main advantage of this technique over existing methods, such as standard extinction training, is that unlike extinction, which might lead to the recovery of fear, interfering with reconsolidation might more permanently modify the fear, memory, and lead to less recovery. The implication of this technique extends toward therapy of anxiety disorders by offering a more permanent way of modifying fear responses.
As circumstances change. To begin clean the subject's fingertips using a Q-tip dampened with distilled water allow the fingertips to dry completely prior to electrode application. Next, apply a highly conductive electrolyte gel to both electrodes.
The gel should rise slightly above the SCR electrode well and not contain air bubbles, which can interfere with the SCR signal. Attach an electrode to the first and second fingers between the first and second phalanges where the electrodermal signal is more pronounced. Ensure the Velcro straps are securely fastened.
Ask the subject to report whether they feel any pulsing in their fingertips. To prevent interference of the SCR signal, loosen the straps if pulsing is recorded. Now that the subject is prepared, load the acknowledged software and save a new file to record SCR for each individual.
The recording screen should be separate from the computer presenting the experimental script and out of the subject's site. Next, begin recording a skin conductance sample for approximately five minutes. Ensure the subject has robust SCR responses by directing them to take in and hold a deep breath.
This should produce a substantial rise in SCR. During the workup procedure, the shock trigger should be unplugged from the stimulator box. Apply a bead of conductance gel to each electrode of the stimulator bar and attach it to the wrist opposite the hand with the SCR electrodes.
Place the bar on the inner wrist to either side of the palm Mars longest tendon and secure it with a nylon Velcro strap. Check to be sure that the strap is not too tight. Now that the stimulator bar is in place, inform the subject that they will receive a series of manually delivered shocks.
Manually trigger a single shock starting at a low level. Continue triggering single shocks while gradually increasing the intensity in five volt increments until the subject indicates that the shock is uncomfortable but not painful. There should be a large SCR to the shocks.
Record the final shock level that was delivered and maintain this voltage level for the remainder of the experiment. When ready to begin, assist the subject in finding a comfortable position that will not require movement. Both arms should be placed in a relaxed position with the wrists supported on a table or the arms of a comfortable chair.
Instruct the subject to breathe naturally. Since abrupt respiratory changes can interfere with SCR, direct the subject to keep their eyes on the screen at all times. Tell the subject that they will see visual stimuli on the screen and receive occasional shocks.
The subject is asked to monitor the relationship between the stimuli they are seeing and the shock received. Once the subject is ready, plug the trigger back into the stimulator box and change the acknowledged setting from off to external. Set the voltage to the correct level and initiate both the acknowledge file and the experimental script.
Each session begins with a screen indicating the experiment is about to start during the acquisition session. One conditioned stimulus or CS is represented by a yellow square and co terminates with a mild shock in a subset of trials. This is referred to as CS plus.
The other conditioned stimulus is represented by a blue square and is never paired with the shock. This is referred to as CS minus conditioned stimuli are presented for four seconds. There is an inter trial interval during which subjects view a black screen with a white fixation point in the center.
The session terminates with a screen indicating that they have successfully completed that part of the experiment on the following day. Randomly divide all subjects that have demonstrated adequate acquisition of fear from day one into three groups as seen here. Group one receives extinction training 10 minutes after retrieval and within the reconsolidation window.
Group two receives extinction training six hours after retrieval outside of this window, and group three receives standard extinction training without any retrieval. Upon arrival, each subject should be set up exactly as they were on day one, instruct the subject to sit comfortably and pay attention to the stimuli presented. Subjects in both reactivation groups undergo a single unreinforced presentation of the CS plus followed by a 10 minute break.
Subjects in the no reactivation group undergo the setup procedure, but then go directly to the break without the reactivation session. During the break, stop the acknowledged recording of the SCR and direct subject's attention to a separate screen that has a preselected TV show. After the break, the reactivation 10 minute group proceeds with extinction training subjects in the reactivation six hour group, return for extinction training six hours later for the no reactivation subjects, half immediately undergo extinction training and half return six hours later for training.
If the subjects demonstrate adequate extinction learning, they should return to the lab 24 hours after their extinction session. Upon arrival, they should be set up as seen previously. Each subject should undergo a re extinction session whereby they again receive unreinforced presentations of both CSS in order to assess the extent to which fear responses recover.
Due to the passage of time at the end of the session, the subject is debriefed and paid before departing. Results from individuals from each experimental condition are seen here at the end of day one. These subjects demonstrated differential SCRs to the conditioned stimuli.
Responses to reinforced cues shown here in red must be higher than those from unreinforced cues shown here in blue In order for subjects to return on day two by the end of day two. These differential responses diminish over time such that there is no longer a difference between responses to the CS plus and CS minus. When examining spontaneous recovery on day three, there is no fear recovery in the reactivation 10 minute group.
Since this group received extinction training within the Reconsolidation window, however, a substantial recovery of fear is seen in the reactivation six-hour group that received extinction training outside of the Reconsolidation window, as well as the no reactivation group that received standard extinction training. Following this procedure, we can now try to interfere with other types of memories in order to answer questions such as, can we interfere with traumatic memories or with rewarding memories associated with addiction and Obesity? After watching this video, you should have a good understanding of how to interfere with reconsolidation of fear memory using a classical conditioning paradigm.
