Zh. Cho et al., EFFECTS OF THE ACOUSTIC NOISE OF THE GRADIENT SYSTEMS ON FMRI - A STUDY ON AUDITORY, MOTOR, AND VISUAL CORTICES, Magnetic resonance in medicine, 39(2), 1998, pp. 331-335
MR acoustic, or sound, noise due to gradient pulsing has been one of t
he problems in MRI, both in patient scanning as well as in many areas
of psychiatric and neuroscience research, such as brain fMRI. Especial
ly in brain fMRI, sound noise is one of the serious noise sources that
obscures the small signals obtainable from the subtle changes occurri
ng in oxygenation status in the cortex and blood capillaries. Therefor
e, we have studied the effects of acoustic, or sound, noise arising in
fMR imaging of the auditory, motor, and visual cortices. The results
show that the effects of acoustic noise on motor and visual responses
are opposite. That is, for motor activity, there is an increased total
motor activation, whereas for visual stimulation, the corresponding (
visual) cortical activity is diminished substantially when the subject
is exposed to a loud acoustic sound. Although the current observation
s are preliminary and require more experimental confirmation, it seems
that the observed acoustic-noise effects on brain functions, such as
in the motor and visual cortices, are new observations and could have
significant consequences in data observation and interpretation in Mur
e fMRI studies.