Subliminal stimuli

Subliminal stimuli are sensations just "below the threshold" of a person's conscious perception. They may be designed to influence the mental processes or the behavior of the individual without beiing noticed.
A recent review of functional magnetic resonance imaging (fMRI) studies shows that subliminal stimuli activate certain parts of the brain, but the subjects do not notice the stimulus. Visual stimuli may be quickly flashed before an individual can process them, or flashed and then masked, thereby interrupting the processing. Audio stimuli may be played below audible volumes or masked by other stimuli.