Brain Stimulation and Vision Testing
- 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.
- This study includes many different experiments on vision. Each experiment may combine visual tasks, MRI scans, and TMS. Participants may be asked to have several different tests. Each test will require a separate visit to the National Institutes of Health.
- Participants will be screened with a physical exam and medical history. They will have a baseline brain scan at the first visit.
- Participants may do visual tasks alone, with MRI only, with TMS only, or with MRI and TMS combined. For the visual tasks, they will look at pictures of objects on a computer screen. Sometimes the images will appear very briefly (less than one-tenth of a second). Sometimes they will appear for up to 5 seconds. These images will be of things like faces, bodies, tools, and scenes. Participants will be asked to respond in different ways to the pictures. They may respond by typing on a computer keyboard or by pressing a button. Participants will have time to practice the tasks before the experiment.
- Participants will remain on the study for up to 3 years.
|Study Design:||Time Perspective: Prospective|
|Official Title:||TMS Investigations of the Human Visual System|
|Study Start Date:||May 2012|
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 240 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.
|Contact: David J Pitcher||(301) firstname.lastname@example.org|
|Contact: Leslie G Ungerleider, Ph.D.||(301) email@example.com|
|United States, Maryland|
|National Institutes of Health Clinical Center, 9000 Rockville Pike||Recruiting|
|Bethesda, Maryland, United States, 20892|
|Contact: For more information at the NIH Clinical Center contact Patient Recruitment and Public Liaison Office (PRPL) 800-411-1222 ext TTY8664111010 firstname.lastname@example.org|
|Principal Investigator:||Leslie G Ungerleider, Ph.D.||National Institute of Mental Health (NIMH)|