None listed
Conditions
Brief summary
This study aims to examine sex differences in the effects of Yohimbine on the neural processing of, and delayed memory for, emotional images. Sex differences will also be explored in the effects of Yohimbine on fear conditioning, and whether this impacts the rate of extinction learning after a delay. Participants will be randomly assigned to recieve either Yohimbine or Placebo. Participants will first undergo a fear conditioning procedure in which they will be presented with coloured circles and a particular colour will be paired with a mild electrical stimulus. Rate of conditioning (or associative fear learning) will be measured via skin conductance responses across trials. Subsequently, in an fMRI scanning machine, all participants will view a series of emotional and neutral images. Two days later, participants will return and undergo a surprise memory test for the images. Following the memory tests, participants will undergo an extinction learning procedure in which skin conductance will be recorded across trials in which the same circles will be presented without any reinforcement (electrical stimulus). The hypothesis is that Yohimbine will enhance amydgala activation during the processing of emotional images, and be associated with superior memory for the emotional images. It is predicted that Yohimbine will enhance the rate of fear conditioning, particularly in women. It is also predicted that the administration of Yohimbine will result in strong amygdala activation during the processing of emotional images as well as the deactivation of prefrontal regions of the brain in participants with higher levels of endogenous cortisol. Finally, it is believed that participants in the Yohimbine group will experience a slower rate of extinction learning after the delay (and particularly in women). All participants and research staff will be blind to the drug contition of the subject until after the study is completed.
Interventions
Healthy male and female participants are either given Yohimbine (20mg) or placebo pill via oral administration. Participants then undergo a fear acquisition paradigm in which they will be shown images of blue and red circles. In a counter-balanced order, one set of coloured circles will be paired with a mild electrical stimulus applied to participants' fingertips at an intensity selected by the participant to be "uncomfortable but not painful". Skin conductance will be used as a measure of condi
Healthy male and female participants are either given Yohimbine (20mg) or placebo pill via oral administration. Participants then undergo a fear acquisition paradigm in which they will be shown images of blue and red circles. In a counter-balanced order, one set of coloured circles will be paired with a mild electrical stimulus applied to participants' fingertips at an intensity selected by the participant to be "uncomfortable but not painful". Skin conductance will be used as a measure of conditioned response to the stimuli. Participants will then undergo a functional magnetic resonance imaging scan (fMRI) where they will view emotional and neutral images. They return two days later to complete surprise recall and recognition memory tasks for the images. At this second session, participants will also undergo a fear extinction paradigm in which they will be presented with the blue and red circles without aversive reinforcement. Skin conductance will again be recorded during this procedure.
Sponsors
University of New South Wales
Study design
Allocation
Randomised controlled trial
Intervention model
Parallel
Primary purpose
Treatment
Masking
Blinded (masking used)
Eligibility
Sex/Gender
All
Age
18 Years to 40 Years
Healthy volunteers
Yes
Inclusion criteria
Healthy University Students. Right handed.
Exclusion criteria
Current course of medication (including hormonal contraceptive for female participants), pregnancy or breasfeeding, substance abuse / dependence, current or recent history of psychiatric conditions, current or recent medical conditions, suicidal thoughts, known sensitivity to Hydrocortisone or Yohimbine, post-menopausal (for female participants), any participants with metal implants in the body. Participants are instructed not to drink alcohol or take any illegal drugs on the day of drug administration, and to abstain from fluids and food for two hours prior to drug administration.
Outcome results
None listed