Brain Stimulation and Vision Testing
|First Received Date ICMJE||June 8, 2012|
|Last Updated Date||December 30, 2015|
|Start Date ICMJE||May 2012|
|Primary Completion Date||Not Provided|
|Current Primary Outcome Measures ICMJE||Not Provided|
|Original Primary Outcome Measures ICMJE||Not Provided|
|Change History||Complete list of historical versions of study NCT01617408 on ClinicalTrials.gov Archive Site|
|Current Secondary Outcome Measures ICMJE||Not Provided|
|Original Secondary Outcome Measures ICMJE||Not Provided|
|Current Other Outcome Measures ICMJE||Not Provided|
|Original Other Outcome Measures ICMJE||Not Provided|
|Brief Title ICMJE||Brain Stimulation and Vision Testing|
|Official Title ICMJE||TMS Investigations of the Human Visual System|
- The brain has two systems for recognizing objects. One system recognizes what an object is, and the other system recognizes where the object is located. However, there is much about how the brain handles and interprets the information from these two systems that is still unclear. Researchers want to study the parts of the brain that are involved in how vision is processed. They will use magnetic resonance imaging (MRI) and transcranial magnetic stimulation (TMS) on the brain. MRI measures what parts of the brain become more active when tasks are performed. TMS uses magnetic pulses to temporarily change the activity in parts of the brain.
- To better understand how people visually recognize different types of objects.
- Healthy volunteers between 18 and 50 years of age.
An influential model of cortical organization proposes that the primate visual system is divided into two functionally distinct pathways (Ungerleider & Mishkin, 1982). The ventral or what visual pathway, which projects from occipital cortex into the ventral temporal cortex, is principally used for object recognition and identification. The dorsal or where pathway, which projects from occipital cortex into the parietal cortex, is principally used for locating the position of objects in the visual field and for action planning (Milner & Goodale, 1995; Kravitz et al., 2011). In the proposed series of experiments we will investigate how neural representations in the ventral and dorsal pathways contribute to a range of cognitive tasks including object and scene recognition, attentional selection and face processing. These experiments will principally use transcranial magnetic stimulation (TMS) in combination with functional magnetic resonance imaging (fMRI).
TMS provides a unique experimental tool for studies of human cognitive function because it can be used to transiently and safely disrupt the neural processing in a targeted cortical region while subjects perform concurrent behavioral tasks that depend on the operations of that region. Furthermore TMS can be combined with neuroimaging techniques such as fMRI to examine the remote effects of the induced neural disruption in other task-dependent regions distributed across cortex. We plan to use TMS to address unanswered questions concerning the functioning of the distributed neural networks for different categories of object recognition and in the attention network of the human brain.
We plan to test 320 neurologically normal subjects aged between 18 and 50 years old. Subjects will also take part in an fMRI experiment prior to any subsequent TMS experiments in order to localize the stimulation sites of interest.
The aim of the proposed series of experiments is to examine the effects of the TMS induced neural disruption on behavioral task performance and the neural correlates of the impaired performance as measured with fMRI. Broadly these experiments can be divided into studies that use online and offline TMS. In on-line experiments, TMS will be applied during behavioral tasks. In off-line experiments, theta burst stimulation (TBS) will be delivered before the experimental task and off-line experiments may combine TBS with fMRI.
- TMS target site localization
Prior to both online and offline studies subjects will take part in an fMRI experiment designed to localize particular cortical regions of interest (ROIs). The fMRI experiment will require the subject to view either a series of different object categories (e.g. faces, bodies, scenes) or flickering sections of black and white checkerboards in the fMRI scanner. The results of these fMRI experiments will be used to identify regions of cortex that will then be targeted with TMS. We will identify TMS target sites using the stereotaxic Brainsight co-registration software and the scalp location will be marked individually on each subject.
-Online behavioral TMS experiments
Online TMS experiments are designed to address the direct effects of the induced neural disruption on the targeted TMS site only. TMS is delivered during every trial to assess the effects on concurrent task performance. Subjects will perform a range of visual behavioral tasks while online TMS is delivered over the cortical region of interest or over control sites (e.g. vertex). Repetitive TMS will be delivered at a frequency of 10Hz for 500ms. In some experiments we will alternatively deliver double-pulse TMS at different latencies after stimulus onset to assess when the targeted region is likely to be involved in task performance.
-Offline TBS experiments
Offline thetaburst (TBS) experiments are also designed to assess the effects of the induced disruption in the stimulated region. However, rather than delivering TMS during every experimental trial Thetaburst TMS (TBS) is delivered over the targeted region of interest (ROI) for latencies up to 60 seconds prior to the subject performing any behavioral task. The neural effects of this induced disruption have then been shown to last for up to 30 minutes (Huang et al., 2005). In the offline TBS experiments we propose to deliver 60 seconds of the TBS over the stimulated ROI. In some of the proposed experiment participants will then be placed in an fMRI scanner before and after TBS stimulation. During both fMRI sessions subjects will perform a series of visual discrimination tasks to assess the effects of TBS disruption both on their behavior and on activity in remote cortical areas as measured with BOLD activation.
The dependent variables in the online behavioral TMS experiments will be performance accuracy, sensitivity (d ) and reaction time (RT) measures collected during the concurrently performed behavioral tasks. Dependent variables in the offline fMRI TBS experiments will be task performance as well as reduced neuronal activity as measured by decreased BOLD activation in the targeted and remote ROIs.
|Study Type ICMJE||Observational|
|Study Design ICMJE||Time Perspective: Prospective|
|Target Follow-Up Duration||Not Provided|
|Sampling Method||Not Provided|
|Study Population||Not Provided|
|Intervention ICMJE||Not Provided|
|Study Group/Cohort (s)||Not Provided|
* Includes publications given by the data provider as well as publications identified by ClinicalTrials.gov Identifier (NCT Number) in Medline.
|Recruitment Status ICMJE||Recruiting|
|Estimated Enrollment ICMJE||320|
|Completion Date||Not Provided|
|Primary Completion Date||Not Provided|
|Eligibility Criteria ICMJE||
Ages 18-50 years (inclusive)
Individuals with conditions that could pose a risk relating to the safety of the MRI procedure, the TMS procedure or the combined TBS and fMRI procedure will be excluded from the protocol such as:
|Ages||18 Years to 50 Years|
|Accepts Healthy Volunteers||Yes|
|Listed Location Countries ICMJE||United States|
|Removed Location Countries|
|NCT Number ICMJE||NCT01617408|
|Other Study ID Numbers ICMJE||120128, 12-M-0128|
|Has Data Monitoring Committee||Not Provided|
|Plan to Share Data||Not Provided|
|IPD Description||Not Provided|
|Responsible Party||National Institutes of Health Clinical Center (CC) ( National Institute of Mental Health (NIMH) )|
|Study Sponsor ICMJE||National Institute of Mental Health (NIMH)|
|Collaborators ICMJE||Not Provided|
|Information Provided By||National Institutes of Health Clinical Center (CC)|
|Verification Date||December 2015|
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