Acoustic or sound noise due to gradient pulsings has been one of the problems in MRI, both in patient scanning as well as in many areas of psychiatric and neuroscience research such as fMRI. Especially in fMRI, sound noise is one of the serious noise sources which obscures the small signals obtainable from the subtle changes occurring in oxygenation status in the cortex and blood capillaries in fMRI.
Therefore, we have tested the effects of acoustic or sound noise arising in fMR imaging of the auditory, motor and visual cortices. It is known that the cerebral blood oxygenation responses to both sustained and repetitive functional activation differ profoundly between a visual and a motor paradigm. Our experimental results show that the acoustical noise effects on motor and visual responses were opposite also. During motor activity, it seems that sound noise makes the subject pay more attention to the mission, thereby resulting in increased total motor activation. For visual stimulation, however, visual stimuli can result in a diminished fMRI when loud acoustic noise exists. Two characteristic differences may be explained by the fact that the motor is self-motivated action while visual stimulation is an external driven stimulation (passive seeing). Although, the current observations are preliminary and requires more experimental confirmation, it appears that acoustic noise effects on brain functions in the motor and visual cortices have significant consequences in data observation and interpretation.