Effects of Prism Adaption and rTMS on Brain Connectivity and Visual Representation

Overview

Background: After a stroke, the balance between the two halves of the brain can be lost. This may cause people to lose the ability to perceive a side of space. This is called neglect. Having people wear prism glasses (called PA) can reduce neglect symptoms. Researchers want to find out more about how PA, and whether it restores the balance in the brain. Objective: To learn how prism adaption temporarily changes vision and connections in the brain. Eligibility: People ages 18 75 with brain damage of the right side of the brain from a stroke or other cause, leading to neglect. Healthy volunteers ages 18 75. Design: Participants will have 1 3 visits. Participants will be screened with a neurological exam. They may also have: Tests of thinking and vision Tests to see which eye and hand they prefer A pregnancy test All participants will: Answer questions about their personality, style of thinking, and beliefs. Do simple tasks on paper or computer Have magnetic resonance imaging. They will lie on a table that can slide in and out of a cylinder in a strong magnetic field. Participants will lie still or do computer tasks in the scanner. Participants may also have: Transcranial magnetic stimulation. A brief electrical current passes through a wire coil on the scalp. This creates a magnetic pulse that affects brain activity. Participants may be asked to tense certain muscles or perform simple actions or tasks. PA. They will sit in front of a board and point to a dot on it while they wear prism glasses that shift vision to the left or right....

OBJECTIVES: The ability to efficiently select information from the environment relies on a balanced interaction between the right and left hemispheres. Hemispatial neglect, most frequently following damage to the right hemisphere, has been hypothesized to result from the breakdown of this interhemispheric balance. There is evidence from transcranial stimulation studies that the breakdown of this interhemispheric balance is reflected in fronto-parietal connectivity. The primary goal of this study is to test whether altering the balance between the left and right hemispheres, with repetitive transcranial magnetic stimulation (rTMS) or prism adaptation (PA), will affect functional connectivity measured with functional magnetic resonance imaging (fMRI). We will also explore the relationship between the changes in functional connectivity and behavioral performances. STUDY POPULATION: Healthy adult volunteers and patients with neglect after a right hemisphere damage. DESIGN: The study contains three experiments. Experiment 1 is designed to investigate the mechanism of the changes induced by PA in both resting state functional connectivity in neglect patients and healthy volunteers (a two-arm parallel study). Experiment 2 is designed to investigate the mechanism of the changes in resting state functional connectivity induced by lPA, rPA, nPA in healthy volunteers with right dominant eyes and lPA in healthy volunteer with left dominant eye (a four-arm parallel study). Experiment 3 is designed to see if inhibitory rTMS over the right posterior parietal cortex (PPC) can influence functional connectivity and visuospatial bias in healthy volunteers (a crossover study). OUTCOME MEASURES: For all three experiments the primary outcome measure is the change (or difference) in fronto-parietal resting state connectivity between post and pre PA or rTMS procedure. The secondary outcome measures are the changes in visual field representation and in visuo-motor and cognitive behavior accompanying these manipulations.