現実的な刺激を用いた知覚のfMRI研究の展望

抄録

The aim of functional magnetic resonance imaging (fMRI) studies of perception is to
unravel the neural basis of the computational processing of the targeted perception. A
standard fMRI study of perception generally uses simple stimuli, such as geometrical
graphics in vision and pure tones in audition, and measures brain responses to such
artificial stimuli, which are generated carefully. The target brain activity of percep-
tual processing has been investigated using a contrast between stimulus conditions, to
cancel out other processes. In contrast, the brain’s response to naturalistic stimuli is
considered not to be a combination of responses to simple stimuli. The uncontrolled per-
ceptual processes that are evoked in parallel hamper the analysis of the data in a simple
factorial manner. In this article, I briefly reviewed fMRI studies that used naturalis-
tic stimuli (e.g., photos and movies) and introduced nonstandard analytical methods.
One was the computational model-based analysis of a hypothesis-driven study, and the
other was the intersubject correlation of data-driven research. A model-based fMRI
study can directly predict the brain responses to the processing of dynamic perception
(e.g., motion perception in the middle temporal area). Intersubject correlation can be
used to evaluate the reliability of fMRI signals in response to naturalistic stimuli. In
addition, I introduced a decoding technique using pattern recognition, which has been
used widely not only in the engineering but also in the neuroscience fields. Although
the number of studies using naturalistic stimuli and novel analytical methods has in-
creased, the standard fMRI study using simple stimuli and analysis remains the most
effective approach to identify the neural bases of perception. I expect that these stan-
dard and novel fMRI studies will contribute complementarily to the elucidation of the
brain processes for naturalistic stimuli.