Effects of Continuous Theta Burst Stimulation on Emotional Attention

University of Cyprus

Status: Completed

Conditions: Healthy Participants

Treatments: Device: Continuous theta burst stimulation; Device: Sham Control

Study type: Interventional

Funder types: Other

Identifiers

NCT07268001

ΕΕΒΚ/ΕΠ/2019/67

Details and patient eligibility

About

The goal of this clinical trial is to examine the differential effect of continuous TBS (cTBS) over the left and right dorsolateral prefrontal cortex (DLPFC) on the facilitation of attention towards emotional (i.e., pleasant and distress-ing) versus neutral stimuli in healthy young adults. The main questions it aims to answer are:

1. To what extend a temporary modulation of DLPFC activity through cTBS influences attentional responses to emotional stimuli?
2. To what extend the effects of cTBS on attentional responses to emotional stimuli differ depending on whether the left or right dorsolateral prefrontal cortex (DLPFC) is stimulated?

Researchers will compare four stimulation conditions: 1) real cTBS on the left DLPFC, 2) real cTBS on the right DLPFC, 3) sham cTBS on the left DLPFC, and 4) sham cTBS on the right DLPFC, to see if participants receiving cTBS over the DLPFC would exhibit faster reaction times to probes replacing pleasant and distressing images, relative to a sham condition.

Participants will receive a short cTBS session (40 seconds), and after that, they will be presented with an emotional dot-probe task (computerized task).

Regarding the cTBS Protocol, coil positioning will be determined using standardized coordinates from the EEG International 10-20 system, with F4 corresponding to the right DLPFC stimulation target and F3 corresponding to the left DLPFC. The location and orientation of each participant's coil placement will be indicated on a nylon cap that participants wore throughout the single stimulation session. A figure-of-eight focal coil (70 mm diameter) will be used. The coil will be held in a fixed position by a mechanical arm and oriented so that the induced electric current flowed in a posterior-anterior direction. Stimulus intensities were set at 70% of active motor threshold (AMT). Each TBS session burst consists of 3 pulses at 50 Hz, with each train being repeated every 200 ms (5 Hz) for 40 seconds (600 pulses).

Regarding the dot-probe task is a common laboratory paradigm used to index attentional bias for emotional stimuli at early stages of information processing. It provides a quick, convenient, and inexpensive index of emotional responsiveness. The emotional pictures version of the task used in the current study presents a series of picture pairs of distressing (e.g., crying child), neutral (e.g., book) and pleasant (e.g., smiling baby) emotional content using images primarily taken from the International Affective Picture System (IAPS). This task consists of 1 block of practice stimuli (12 picture pairs) followed by 3 experi-mental blocks, each containing 12 picture pairs. Each picture presentation had three sequential components: (1) a 500 millisecond image of fixation cross appearing in the center of the screen, (2) a 500 millisecond simultaneous presentation of one of three potential picture pairings: neutral-neutral, pleasant-neutral and distress-neutral, with stimuli centered and located above or below the location of the fixation cross, and (3) a second image of fixation cross appearing in either the top or bottom picture location. Participants will be instructed to respond as fast as they could and after every trial they selected a key on the keyboard that corresponded to the location on the screen (up or down) where the dot-probe appeared. If no key was pressed within 5000 milliseconds, the response will be recorded as incorrect.

Enrollment: 91 patients

Sex: All

Volunteers: Accepts Healthy Volunteers

Inclusion criteria

• Medication-free, right-handed, normal vision, without ant estabished risk factor to rTMS (screening performed with Transcranial Magnetic Stimulation Safety Questionnaire).

Exclusion criteria

• History of psychiatric/neurological disorders, such as epilepsy, head trauma and migraine.

Trial design

Primary purpose: Basic Science

Allocation: Randomized

Interventional model: Parallel Assignment

Masking: Single Blind

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91 participants in 4 patient groups

cTBS over the left DLPFC

Experimental group

Description:

Participants receive 1 session of continuous theta burst stimulation (cTBS) over the left dorsolateral prefrontal cortex (DLPFC; F3, following standard coordinates from the EEG International 10-20 system). The TBS sesssion consisted of 3 pulses at 50 Hz, with each train being repeated every 200 ms (5 Hz) for 40 seconds (600 pulses). After stimulation, attentional responses to pleasant and distressing images are assessed using the dot-probe task, which measures attentional bias toward emotional stimuli by presenting pairs of pleasant-neutral, distressing-neutral and neutral-neutral images. After each image pair, a dot appears in the location of one image, and participants must quickly indicate its position.

Treatment:

Device: Continuous theta burst stimulation

cTBS over the right DLPFC

Experimental group

Description:

Participants receive 1 session of continuous theta burst stimulation (cTBS) over the right dorsolateral prefrontal cortex (DLPFC; F4, following standard coordinates from the EEG International 10-20 system). The TBS sesssion consisted of 3 pulses at 50 Hz, with each train being repeated every 200 ms (5 Hz) for 40 seconds (600 pulses). After stimulation, attentional responses to pleasant and distressing images are assessed using the dot-probe task, which measures attentional bias toward emotional stimuli by presenting pairs of pleasant-neutral, distressing-neutral and neutral-neutral images. After each image pair, a dot appears in the location of one image, and participants must quickly indicate its position.

Treatment:

Device: Continuous theta burst stimulation

sham cTBS over the left DLPFC

Sham Comparator group

Description:

Participants receive 1 session of sham continuous theta burst stimulation (cTBS) over the left dorsolateral prefrontal cortex (DLPFC; F3, following standard coordinates from the EEG International 10-20 system). Sham stimulation was delivered using a sham coil that produced the same stimulation noise, but inducing nearly zero electric-field under the coil's center. After sham stimulation, attentional responses to pleasant and distressing images are assessed using the dot-probe task, which measures attentional bias toward emotional stimuli by presenting pairs of pleasant-neutral, distressing-neutral and neutral-neutral images. After each image pair, a dot appears in the location of one image, and participants must quickly indicate its position.

Treatment:

Device: Sham Control

sham cTBS over the right DLPFC

Sham Comparator group

Description:

Participants receive 1 session of sham continuous theta burst stimulation (cTBS) over the right dorsolateral prefrontal cortex (DLPFC; F3, following standard coordinates from the EEG International 10-20 system). Sham stimulation was delivered using a sham coil that produced the same stimulation noise, but inducing nearly zero electric-field under the coil's center. After sham stimulation, attentional responses to pleasant and distressing images are assessed using the dot-probe task, which measures attentional bias toward emotional stimuli by presenting pairs of pleasant-neutral, distressing-neutral and neutral-neutral images. After each image pair, a dot appears in the location of one image, and participants must quickly indicate its position.

Treatment:

Device: Sham Control