Brain Activation Associated With Visual Motion Studied by Functional Magnetic Resonance Imaging in Humans

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Localized brain activation in response to moving visual stimuli was studied by functional magnetic resonance imaging (fMRI). Stimuli were 100 small white dots randomly arranged on a visual display. During the Motion condition, the dots moved along random, noncoherent linear trajectories at different velocities. During the Blink condition, the dots remained stationary but blinked on and off every 500 ms. The Motion and Blink conditions continuously alternated with 10 cycles per run and 6-8 runs per experiment. In half of the runs, the starting stimulus condition was Motion, while in the remaining runs it was Blink.

A series of 128 gradient echo echoplanar images were acquired from 5-7 slices during each run using a 1.5 T GE Signa with an Advanced NMR echoplanar subsystem. The time series for each voxel were analyzed in the frequency domain. Voxels which demonstrated a significant spectral peak at the alternation frequency and whose phase changed in response to stimulus order were considered activated. These activated voxels were displayed upon high resolution anatomical images to determine the sites of activation and were also transformed into the coordinates of Talairach and Tournoux ([1988] Co-planar Stereotaxic Atlas of the Human Brain, New York: Thieme) for comparison to prior neuroimaging studies.

Seven of ten subjects showed clusters of activation bilaterally at the junction of the temporal and occipital lobes (area 37) in response to moving stimuli. Most activated voxels were located within or adjacent to a region designated the parietal-temporal-occipital fossa, or PTOF. Five subjects also showed activation to moving stimuli in midline occipital cortex. The activated voxels in midline cortex had a significantly shorter phase delay in their MR signal change relative to voxels in PTOF.

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