The existence of perceptually
robust multisensory interactions, such as the ventriloquism and McGurk effects,
has been well established in behavioral studies, and neuroimaging studies have
further shown that multisensory processing of stimuli takes place even in
primary sensory cortical areas. There is also evidence suggesting that mental
imagery, such as an imagined sound of a hammer seen to hit an anvil in a silent
movie, modulates processing in sensory cortical areas. What has remained less
explored is the extent that imaginary visual stimuli influence processing of
real auditory stimuli and vice versa.
In their recently published
study, Berger and Ehrsson (2013) conducted a series of behavioral experiments
where they tested whether imagined stimuli cause well-known multisensory
illusory percepts similarly as real stimuli. They first tested the effects of
an imagined sound of collision on cross-bounce illusion, followed by testing
the effects of an imagined visual stimulus on ventriloquism effect, and as a
third test, the effects of an imagined seen articulation on the so-called
McGurk effect. In all three experiments, the authors were able to demonstrate
that imagined stimulus causes similar multisensory illusions as real cross-modal
stimuli; imagining the sound of a collision gave rise to the cross-bounce
illusion, imagining a visual stimulus shifted the perceived location of an
auditory stimulus, and auditory imagery of speech stimuli led to a promotion of
an illusory speech percept, i.e., in
a modified McGurk illusion.
These highly exciting results nicely
expand previous findings on multisensory interactions, and provide further
evidence for the view that sensory cortices play a pivotal role in generation
of mental imagery – even to the extent that visual imagery modulate processing
of auditory stimuli and vice versa.
It is easy to see that these behavioral results also provide an excellent
starting point for further neuroimaging studies investigating the multisensory
effects of mental imagery in sensory cortical areas of the brain.
Reference: Berger CC, Ehrsson HH. Mental imagery changes
multisensory perception. Current Biology (2013), e-publication ahead of print.
This is cool!
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