Attention and Visual Perception
|The safety and scientific validity of this study is the responsibility of the study sponsor and investigators. Listing a study does not mean it has been evaluated by the U.S. Federal Government. Read our disclaimer for details.|
|ClinicalTrials.gov Identifier: NCT00111293|
Recruitment Status : Completed
First Posted : May 19, 2005
Last Update Posted : July 2, 2017
The NIMH is conducting studies aimed at gaining a better understanding of the areas of the brain that are involved in different types of mental processes. This study will focus on brain regions involved in visual perception and attention.
Healthy normal volunteers and people who have had a stroke or undergone neurosurgery may be eligible for this study. Candidates must be 18 years of age or older, They must not have a history of a psychiatric disorder, including depression, anxiety, psychosis, or neurological disease other than stroke or the previous neurosurgery.
Participants undergo the following tests and procedures during four or more visits to the NIH Clinical Center:
- Physical and neurological examinations and depression rating scale.
- Cognitive testing: Subjects complete written tests, sit at a computer and make decisions about what they are shown by pressing keys, or answer questions from a test examiner.
- Behavioral training: Subjects practice performing a cognitive task that involves looking at and making decisions about visual images that appear on a computer screen.
- Magnetic resonance imaging (MRI): Subjects undergo MRI scanning while they perform the task they previously practiced. The MRI scanner is a metal cylinder surrounded by a strong magnetic field. During the procedure, subjects lie still for up to 10 minutes at a time on a table that can slide in and out of the cylinder. The entire MRI scanning session takes about one hour. There are multiple scans which each can take up to 10 minutes. They may be asked to return for one or two additional scanning sessions.
During the behavioral training or MRI scanning, special pieces of equipment that monitor eye movements may be used.
Some subjects may be asked to return to NIH for an additional visit to participate in a magnetoencephalographic scan. This test uses several sensors applied to the scalp to measure very small changes in magnetic fields. This is another way to measure brain activity.
|Condition or disease|
|Focal Lesions Focal Brain Lesion|
Attention is required for most, if not all, perceptual processes. There is a converging body of evidence from single-cell recording studies in monkeys and neuroimaging, behavioral, and clinical studies in humans showing that the processing of attended information is enhanced relative to the processing of unattended information.
What is the source of this attentional modulation? Because neuroimaging studies have demonstrated that multiple cortical regions are recruited during tasks involving selective attention, it has proven difficult thus far to determine the differential contributions of each region. A central goal of the proposed research is to characterize the contributions of prefrontal cortex and parietal cortex and test the hypothesis that these regions exert top-down modulatory influences over visual processing areas. Specifically, we wish to investigate the interaction between areas involved in attentional control and visual areas modulated by attention.
We propose to study patients with focal lesions and normal volunteers while they perform tasks requiring attention. Subjects will participate, first, in a series of behavioral studies involving selective attention; the relative performance of different patient groups and neurologically normal volunteers will be compared. Subjects will also be studied while performing similar tasks during functional magnetic resonance imaging (fMRI). We hypothesize that selective attention will be heavily impaired by lesions of key prefrontal (e.g., dorsolateral prefrontal cortex) and key parietal (e.g., superior parietal lobule) sites. We also expect that brain imaging data will show decreased activation in visual regions ipsilateral to the focal lesions in prefrontal and parietal cortex, thus providing evidence that prefrontal and parietal cortex are sources of top-down modulation. Although other research groups have compared the behavior of patients with various focal lesions or have performed fMRI studies of visual attention in neurologically normal patients, we are unaware of any concerted effort to perform fMRI in patients with focal lesions in order to functionally isolate the contributions of individual cortical regions that serve as critical nodes in the attentional network.
|Study Type :||Observational|
|Actual Enrollment :||8 participants|
|Official Title:||Top-Down Attentional Control of Visual Processing|
|Study Start Date :||May 16, 2005|
|Estimated Study Completion Date :||May 14, 2010|
To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.
Please refer to this study by its ClinicalTrials.gov identifier (NCT number): NCT00111293
|United States, Maryland|
|National Institutes of Health Clinical Center, 9000 Rockville Pike|
|Bethesda, Maryland, United States, 20892|