This video demonstrates the use of Duke's immersive virtual environment, DIVE, to generate lifelike fear conditioning data in humans. Virtual worlds are created with virtual software and code is generated to elicit stimuli.Presentations. The participant is set up with electrodes for skin conductance recording and wrist stimulation, as well as button presses within the virtual reality setting.
Skin conductance response and button press data are then collected while dynamic stimuli are presented in the DIVE, physiological data and expectancy measures are analyzed to demonstrate fear acquisition, fear extinction, and fear of memory retention to condition stimuli, or context. Hi, I'm Kevin Lebar. I'm a professor at the Center for Cognitive Neuroscience at Duke University.
I am Rachel Brady, director of the Duke Immersive Virtual Environment. Hi, my name is Nicole Huff. I'm a postdoctoral associate in Dr.Lamar's Laboratory.
Hello, my name is David Zelensky from the Visualization Technology Group. Today we will show you a procedure for conducting human fear conditioning experiments using fully immersive three-dimensional virtual reality. We use this procedure to examine contextual influences on fear acquisition and memory retention.
So let's get started. To examine contextual influences on fear acquisition and memory, human participants are presented with dynamic condition stimuli in a fully immersive virtual environment known as Duke's Immersive virtual environment. The dive system consists of a three meter by three meter by three meter room, in which all four walls, the ceiling and the floor shows stereographics computer images by rear projection.
Each wall has its own DLP projector, which in turn is controlled by a dedicated computer. One of the wall slides open to allow access into and out of the DIVE, there is a tracking system that provides 3D location and orientation information for the participant's head and hand positions. Active stereo vision is provided through liquid crystal shutter glasses worn by participants.
The six wall dedicated computers are controlled by a master computer that communicates to the tracking system, controls the sound system, and controls an electrical shock system, which is used for fair conditioning. The seven computers are synchronized on image frame boundaries through the genlock capability of their NVIDIA graphics cards. Navigation through the virtual environment is limited to a fixed path that is identical in all virtual worlds.Movement.
Along this path is controlled through the virtual software system. VIRs communicates with the tracking system through the virtual reality peripheral network and open source library. VRPM registers the participant's head and hand location and orientation, as well as button press information.
OLS uses the head tracking information to render the 3D scene at the correct perspective for the participant. Now let's see how to set up a participant for a fair conditioning experiment within the DIVE system. During fair conditioning experiments, inside the DIVE participants encountered dynamic condition stimuli consisting of snakes and spiders paired with electrical wrist stimulation before starting the conditioning procedure first, randomly assign each participant to a particular condition, stimulus term the CS plus stimulus consisting of either snake images or spider images for all participants.
The uncondition stimulus to be paired with the CS plus stimulus consists of electrical stimulation of the wrist for each participant. The stimulus that was not selected to be the CS plus serves as a control and is termed the CS minus stimulus. Now, randomly assign the participant a particular virtual context in which he or she will view the stimuli.
One possible virtual reality context consists of an indoor environment, and the other context consists of an outdoor environment to set up the electrical stimulation that will be paired with the CS plus stimulus. Apply a small amount of conductive gel onto the electrodes, then secure a bipolar surface stimulation electrode over the median nerve of the participant's dominant wrist, secure the electrode leads by a rubber strap and attach them to a grass tele factor SD nine stimulator. Now to find the appropriate stimulation voltage, start with the voltage set at a low level of 30 volts and stimulate for 200 milliseconds.
At 30 to 50 hertz, increasing the voltage in increments of five volts until the participant indicates that their tolerance level has been reached without inducing pain. The goal is to find a setting that is perceived as highly annoying but not painful. The dependent measure of fear in human participants during this experiment is the skin conductance response.
Participants should first wash and dry their hands while they wait at least 10 minutes to acclimate to the temperature of the building. Before attaching the SCR electrodes, exfoliate the middle phalanges of the first and second digits of the non-dominant hand with new prep, wipe them dry and then apply a small amount of Cigna conductive gel in the electrode. Now to measure SCR, attach silver, silver chloride electrode discs to the middle for land use of the first and second digits of the non-dominant hand.
The leads reach a BioPack physiological recording system located just outside the DIVE in the control room. The bio system synchronizes with the stimulus presentation, computer running T'S software wear with the electrical stimulus and SCR electrode set up seat. The participant in the center of the dive facing forward with head tracking on the 3D eyeglasses in the dominant hand place, the one device which will record button press responses from the participant when they encounter a snake or spider.
Now inform the participant that their task is to indicate with a button press on the wand how likely they think it is that they will receive electrical stimulation When encountering a snake or spider, the buttons are ordered from left to right, left being least likely to receive stimulation. Remind them that the button press does not influence the occurrence of electrical stimulation. Now let's see the fair conditioning experiments.
The fair conditioning experiment is conducted over two sessions separated by 24 hours. The first session consists of an initial habituation period immediately followed by the fear acquisition phase. The second session consists of memory, retention, testing, and extinction training during the initial habituation period.
Present the participant with four trials of each CS type viewed on a great background in 3D full immersion, but without reinforcement or the virtual world in which training or testing will occur in each trial, the stimulus appears for four seconds and co-occur with a rattle or tapping sound to signal the appearance of a snake or spider. This phase allows for acclimation to the experimental environment in the DIVE and reduction of orienting responses to the condition stimuli. Immediately following the habituation phase, begin the fear acquisition phase.
Present 16 intermix trials of each CS type in which the CS minus is presented alone and five of the 16 CS plus trials are reinforced with electrical stimulation approximately 24 hours later. Begin the second session. In this phase, present the participant with 16 trials of H Cs type with no electrical stimulation in a virtual context that is either the same as or different from the fear acquisition context depending on which group the participant was initially assigned to.
The task and instructions to the participant are the same as at the second session. Now we'll show some results from fair conditioning experiments in the DIVE equivalent within session Fair acquisition and extinction across groups was found indicating that reliable and informative fear conditioning studies can be performed within the constraints and capabilities of a fully immersive environment. Moreover, in participants who remained in the same context for days one and two of the experiments, there was robust contextual fear memory relative to those who experienced a context shift.
The retention of fear is stronger in the DIVE than in a conventional laboratory matched paradigm. We've just shown you how to conduct human fear conditioning experiments using fully immersive virtual reality. This technology is useful for examining contextual influences over fear of memory.
And remember, when conducting these experiments, it's important to constrain the capabilities of virtual reality so that you can generate interpretable data. For example, you want to control how much a participant moves as well as placement and duration of stimuli. So that's it.
Thanks for watching and good luck with your experiments.
