Brain Connectivity Between Visual Input and Movement

OBJECTIVE:

The purpose is to analyze task-related connectivity changes in brain regions, using a block design blood oxygenation level-dependent functional magnetic resonance imaging (BOLD-fMRI), as a function of the linkage between visual input and motor output.

STUDY POPULATION:

• 25 right-hand dominant, healthy adult volunteers

DESIGN:

Connectivity between brain areas can change related to the dependence level between visual input and motor output. The dependence level will be modulated while performed tasks engage visual and motor areas either in a functionally related fashion or not. Subjects will perform a visuomotor task (VM, dependence level = maximal) that consists of tracking a target by exerting force isometrically on a transducer with their right index finger (target signal and exerted force are displayed in the scanner). In the visual plus motor task (V+M), two different tasks will be performed simultaneously. Subjects will perform the same motor task as in VM but without target signal and visual feedback of their force control, while a neutral visual input unrelated to the motor output is dynamically flashed in the screen. In the visual (V), subjects will watch the target signal while relaxed. In the motor task (M), subjects will produce the same motor task as in VM and V+M while staring at a static fixation cross. A rest period will require subjects to fixate on a stationary dot in the middle of the visual field. fMRI scanning will be used to record brain activity during tasks.

The experimental phase will have six sets of 6-minute scanning sessions where the subject will perform the conditions. The conditions will appear pseudo-randomly throughout the scan sessions. V will always precede VM condition to avoid motor system activation secondary to imagination of movement primed by the visual stimulus. The M and VM conditions will be presented in a random order. At the completion of fMRI scanning, a baseline high-resolution MRI T1 scan will be obtained for anatomic localization and co-registration.

OUTCOME MEASURES:

The primary outcome is the connectivity change in brain networks in response to loss of dependence between a sensory input and the motor output. We will be focused on the correlation between the time series of activations in each condition and the connectivity changes over all the conditions. This will allow us to elucidate the task-dependent connectivity between occipital cortex and prefrontal cortex relative to the functional link between visual input and motor output.

• INCLUSION CRITERIA:
• Subjects age 18 and older
• Subjects must be right-hand dominant (Edinburgh Handedness Quotient greater than 60)
• Subjects willing to abstain from caffeine or alcohol for 48 hours prior to the fMRI scanning

Exclusion criteria

• Subjects with any abnormal findings on neurological exam
• Subjects who are pregnant (as determined by a positive urine pregnancy test)
• Subjects with any finding on the MRI safety questionnaire which prevents them from safely undergoing an MRI scan
• Subjects with metallic dental fillings which are likely to cause MRI artifacts
• Subjects with any history of brain tumor, stroke, head trauma or a vascular malformation as obtained by history or from imaging studies
• Subjects with any history of a severe medical condition, such as cardiovascular disease, which would prevent them from lying flat for up to 120 minutes
• Subjects without the capacity to give informed consent
• Subjects with claustrophobia or other restrictions which prevent them from undergoing a scan in a confined space for up to 60 minutes