The Role of Different Prefrontal Areas in Visual Metacognition

The study will use transcranial magnetic stimulation (TMS) to investigate the causal role of different brain regions during visual perception. TMS is a well-established technique used by hundreds of labs in the world. The risks associated with the technique are well understood and can be minimized by strict adherence to established safety guidelines. In the proposed study, the investigators will use TMS to specifically address the topic of how metacognitive evaluation is supported by the two prefrontal areas: the dorsolateral prefrontal cortex (DLPFC) and the anterior prefrontal cortex (aPFC). The data will be collected from healthy adults and will ultimately deepen the investigator's understanding of the mechanisms behind the normal processes related to confidence generation and metacognition.

Study Overview

• Status: Completed
• Conditions: Healthy
• Intervention / Treatment: Other: Transcranial magnetic stimulation

Detailed Description

Participants will complete a task on visual perception and receive TMS in order to assess which regions of the brain are important for confidence generation in perceptual tasks. The task will involve judging the identity of visual stimuli (oriented black-and-white gratings) and providing a confidence rating on the judgment that they performed.

The researchers will deliver TMS to several brain regions such as the anterior prefrontal cortex (aPFC), dorsolateral prefrontal cortex (DLPFC), and a control site. The researchers will then investigate participants' accuracy and confidence levels depending on where TMS was delivered. The researchers expect that aPFC TMS will decrease the metacognitive sensitivity of the participants, whereas DLPFC TMS will decrease their average confidence level. TMS will be delivered time locked to the onset of the stimulus and the researchers will investigate what is the critical period of involvement of a given region.

The TMS protocol is well within the established safety limits. Participants will be required to fill out screening and demographic forms delivered at the Center for Advanced Brain Imaging (CABI). In order to dose appropriately the TMS stimulation, it is necessary to perform motor threshold determination. Motor threshold (MT) is defined as the minimum magnetic flux needed to elicit a visual hand twitch (in the contralateral first dorsal interosseus muscle). MT is the standard in the field for determining the intensity of TMS for each individual to reduce seizure risk. The scalp region producing the largest hand twitch will be identified. At that scalp location, the lowest TMS intensity able to elicit 5 visible twitches in 10 trials at this site will be determined. Individual MT will be used to determine the intensity of stimulation for each individual, as recommended by safety guidelines. This procedure usually takes about 5 minutes and also serves the purpose of acquainting participants to TMS stimulation. In this study, the researchers will use intensities between 100 and 120% of MT, even though the safety guidelines allow for stimulation intensities of at least 130% of MT.

• Study Type: Interventional
• Enrollment (Actual): 76
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United States
  • Georgia
    • Atlanta, Georgia, United States, 30332
      • Center for Advance Brain Imaging

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 40 years (Adult)
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• right-handed
• adults 18-40
• with normal or corrected-to-normal vision

Exclusion Criteria:

• history of seizures
• family history of epilepsy
• stroke
• severe headaches
• metal anywhere in the head (excluding the mouth)
• cardiac pacemakers
• current use of medication for neurological or psychiatric conditions

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Healthy Adult Volunteers; The experiment has a within-subject design where each subject will receive TMS to different brain areas. The analysis will involve comparing the effects of TMS to different regions.	Other: Transcranial magnetic stimulation; TMS will be delivered to different brain areas in order to establish their contribution to visual metacognition.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Average Confidence Difference With the 0 ms Condition	The average confidence difference for each delay condition and the 0 ms condition for each group (DLPFC or vertex). Confidence was self-reported together with the decision on a 4-point scale with the minimum score being one (not confident at all) and the highest score being four (very confident). The range of the scale is 1 (not confident at all) to 4 (very confident).	6 months
Average Mratio Difference With the 0 ms Condition	The average Mratio difference for each delay condition and the 0 ms condition for each group (DLPFC or vertex). The Mratio is derived from signal detection theoretical modeling of the observer's decision and confidence response. It is the ratio of two measures: the observer's metacognitive sensitivity (meta-d', the ability to discriminate between correct and incorrect responses) and the observer's stimulus sensitivity (d', the ability to discriminate between the two stimulus classes). The Mratio could be calculated from subjects' self-rated confidence together with task performance.	6 month

Collaborators and Investigators

• Sponsor: Georgia Institute of Technology
• Collaborators: National Institute of Mental Health (NIMH)
• Investigators: Principal Investigator: Dobromir A. Rahnev, Ph.D., Georgia Institute of Technology

Study record dates

Study Major Dates

• Study Start (Actual): February 22, 2022
• Primary Completion (Actual): August 31, 2022
• Study Completion (Actual): August 31, 2022

Study Registration Dates

• First Submitted: February 7, 2020
• First Submitted That Met QC Criteria: February 10, 2020
• First Posted (Actual): February 11, 2020

Study Record Updates

• Last Update Posted (Actual): September 15, 2023
• Last Update Submitted That Met QC Criteria: September 12, 2023
• Last Verified: August 1, 2023

More Information

Terms related to this study

• Keywords: Transcranial Magnetic Stimulation; Prefrontal Cortex; Metacognition
• Other Study ID Numbers: H20033; 5R01MH119189 (U.S. NIH Grant/Contract)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No