From Attention to Behavior: Increasing Behavioral Inhibition Through Transcranial Direct Current Stimulation in Pedophilia
Trial Snapshot
- Phase
- Not Applicable
- Sponsor
- University of Zurich
- Enrollment
- 76
- Locations
- 1
- Primary Endpoint
- differential AAT index (∆RT)
Study Overview
Brief Summary
This project will investigate if transcranial direct current stimulation can be used as treatment for Pedophilia. Treatment efficacy will be evaluated with behavioral tasks and the recording of eye-movement.
Detailed Description
Pedophilia is an important motivation for sexual offenses involving children, including child pornography and sexual contacts with children (henceforth, pedosexual behavior). Indeed, approximately half of individuals convicted for sexual offenses against children have a Pedophilic disorder and offenders with a Pedophilic disorder are much more likely to sexually reoffend.
A promising line of research has examined the neurocognitive basis of pedophilia. Pedophilic individuals display altered activity in the dorsolateral prefrontal cortex (dlPFC) when attending to child-related stimuli. This brain area is involved in the cognitive control of sexual arousal. Transcranial Direct Current Stimulation (tDCS) has been examined as a non-invasive method to increase activity in the dlPCF, ultimately increasing inhibitory control over impulses. Accumulating evidence also shows that individuals have an attentional bias towards sexually preferred stimuli. These attentional processes can be investigated by recording eye movements. Early automatic eye movements are particularly relevant in discriminating individuals with pedophilia from those without pedophilia.
The proposed study will examine the effects of tDCS over the dlPFC of pedophilic individuals and healthy controls, while they complete a task requiring controlled attention to virtual (computer-generated) images of children and adults. In two separate sessions, participants will be randomly assigned to an active and a placebo (sham) tDCS condition. Eye movements will be recorded during the task.
The investigators expect to observe a conflict between automatic and controlled attention when participants are presented with their sexually preferred stimuli. Specifically, the investigators expect pedophiles to show an attentional bias towards virtual child stimuli. The investigators predict that the attentional conflict will be reduced when tDCS is applied, compared to the sham condition. If the attentional bias is a key cognitive feature of sexual interest, the investigators expect to measure changes in reported or indirectly assessed sexual preferences.
Study Design
- Study Type
- Interventional
- Allocation
- Randomized
- Intervention Model
- Parallel
- Primary Purpose
- Treatment
- Masking
- Double (Participant, Investigator)
Eligibility Criteria
- Ages
- 18 Years to 65 Years (Adult, Older Adult)
- Sex
- Male
- Accepts Healthy Volunteers
- Yes
Inclusion Criteria
- •Diagnosed with pedophilia (further psychiatric illnesses possible)
- •Sufficient German language skills
- •Not diagnosed with Pedophilia (or other psychiatric illnesses)
- •Sufficient German language skills
Exclusion Criteria
- •Prior head injury with loss of consciousness for at least 5 min
- •Neurological diagnosis (including epilepsy) or prior medical conditions with possible central nervous system sequelae
- •Metallic implants inside the brain or any electrical medical device (e.g. pacemaker) in the body
- •Visual or hearing impairment, to the extent that it interferes with task instructions
- •Current medication in patients (antiandrogenic medication among the pedophilic subjects, in particular) will be recorded and acknowledged as a covariate.
- •Prior head injury with loss of consciousness for at least 5 min
- •Neurological diagnosis (including epilepsy) or prior medical conditions with possible central nervous system sequelae
- •Metallic implants inside the brain or any electrical medical device (e.g. pacemaker) in the body
- •Visual or hearing impairment, to the extent that it interferes with task instructions
- •Current or previous pedophilic sexual interest
- •For both groups further exclusion (prematurely) will occur if initial data shows that participants don't comply with instructions or if questionnaires hint toward a lack of sexual interest in general.
Arms & Interventions
Antisaccade Task (active tDCS)
During the antisaccade task, the investigators will show participants computer-generated images depicting clothed and sexually relevant (nude) children, young adults and adults of both genders. Images will be drawn from the Virtual People Set and the Not-Real-People Set (Pacific Psychological Assessment Corporation, 2004). Pedophilic participants are expected to show a sexual preference towards a prepubescent body scheme whereas stimuli displaying adolescence and adulthood (sexual maturity) are expected to be sexually preferred by the teleiophilic control participants. In this arm active Transcranial Direct Current Stimulation will be used to influence performance.
Intervention: Transcranial Direct Current Stimulation (Device)
Antisaccade Task (sham tDCS)
During the antisaccade task, the investigators will show participants computer-generated images depicting clothed and sexually relevant (nude) children, young adults and adults of both genders. Images will be drawn from the Virtual People Set and the Not-Real-People Set (Pacific Psychological Assessment Corporation, 2004). Pedophilic participants are expected to show a sexual preference towards a prepubescent body scheme whereas stimuli displaying adolescence and adulthood (sexual maturity) are expected to be sexually preferred by the teleiophilic control participants. In this arm sham Transcranial Direct Current Stimulation will be used during the task.
Intervention: Transcranial Direct Current Stimulation (Device)
Approach Avoidance Task (active tDCS)
During the Approach-Avoidance Task (AAT), participants will look at a series of images depicting children and adults wearing swimsuits. The images were sampled from internet advertisements and do not constitute legally objectionable material. When sourcing the images, rigorous attention was paid to meet the criteria for fair use indicated by the American Psychological Association. There are 160 images in total. Half of the images will be used in the active and the other half in the sham condition (i.e., 20 female adults, 20 female children, 20 male adults, and 20 male children per condition). In this arm active Transcranial Direct Current Stimulation will be used to influence performance.
Intervention: Transcranial Direct Current Stimulation (Device)
Approach Avoidance Task (sham tDCS)
During the Approach-Avoidance Task (AAT), participants will look at a series of images depicting children and adults wearing swimsuits. The images were sampled from internet advertisements and do not constitute legally objectionable material. When sourcing the images, rigorous attention was paid to meet the criteria for fair use indicated by the American Psychological Association. There are 160 images in total. Half of the images will be used in the active and the other half in the sham condition (i.e., 20 female adults, 20 female children, 20 male adults, and 20 male children per condition). In this arm sham Transcranial Direct Current Stimulation will be used during the task.
Intervention: Transcranial Direct Current Stimulation (Device)
Outcomes
Primary Outcomes
differential AAT index (∆RT)
Time Frame: Through study completion, an average of 10 months. The outcome measure is not an event but a performance measure recorded for every participant in every session.
In the Approach-Avoidance Task (AAT) the differential AAT index (∆RT) will be recorded in both active and sham tDCS condition using the response on the joystick. The proportion of correct/incorrect responses (%) will inform us about automatic attentional processes. Thus the ∆RT is a single performance index for speed tests measured with a unit of time, in this case Milliseconds (ms). It gives information on how fast participants responded using the joystick. In addition, the percentage (%) of correct responses with the joystick will be recorded. Since the task is not difficult, the percentage values only serve to check for compliance and if task instructions were understood. The real focus of the study lies in the RT as recorded with ∆RT in ms.
Entry Time
Time Frame: Through study completion, an average of 10 months. The outcome measure is not an event but a performance measure recorded for every participant in every session.
In the Antisaccade task entry time will be recorded with an eye-tracker in both active and sham tDCS conditions. Time to first fixation (entry time) is defined as the time from stimulus onset to the first fixation directed to the target stimulus. This index can be treated as reaction time (RT) and will provide a measure of controlled attention. The location of the first fixation indicates which stimulus captures subject's automatic attention. The proportion of correct/incorrect fixations (%) will inform us about automatic attentional processes. Thus entry time is a single performance index measured with a unit of time, in this case Milliseconds (ms). Every participant's performance in the Antisaccade task will be measured with entry time (ms) as well as the percentage (%) of correct responses. Since the task is not difficult, the percentage values only serve to check for compliance with task instructions. The real focus of the study lies in the RT as recorded with entry time in ms.
Secondary Outcomes
No secondary outcomes reported