Visual feedback to stabilize head position for fMRI

Visual feedback to stabilize head position for fMRI.

Head motion is a common cause of technical failure in functional magnetic resonance imaging. A simple visual alignment system has been developed to provide visual feedback to the subject about his or her head position. The subject is able to readjust his or her head position accurately during a study, should motion occur. This sighting system is incorporated into a visor that fits onto the comm...

An fMRI study of human visual cortex in response to spatiotemporal properties of visual stimuli

  ABSTRACT  Background: The brain response to temporal frequencies (TF) has been already reported, but with no study reported for different TF with respect to various spatial frequencies (SF).  Materials and Methods: fMRI was performed by 1.5T GE-system in 14 volunteers during checkerboard, with TFs of 4, 6, 8 and 10Hz in low and high SFs of 0.5 and 8cpd.  Results: Average percentage BOLD signa...

Feedback Regulation of Limb Position Characterized Using fMRI

an fmri study of human visual cortex in response to spatiotemporal properties of visual stimuli

abstract  background: the brain response to temporal frequencies (tf) has been already reported, but with no study reported for different tf with respect to various spatial frequencies (sf).  materials and methods: fmri was performed by 1.5t ge-system in 14 volunteers during checkerboard, with tfs of 4, 6, 8 and 10hz in low and high sfs of 0.5 and 8cpd.  results: average percentage bold signal ...

Asymptotic position control of robot manipulators using uncalibrated visual feedback

To implement a visual feedback controller, it is necessary to calibrate the homogeneous transformation matrix between the robot base frame and the vision frame besides the intrinsic parameters of the vision system. The calibration accuracy greatly a ects the control performance. In this paper, we address the problem of controlling a robot manipulator using visual feedback without calibrating th...