  Although functional magnetic resonance imaging (fMRI) is widely used for the
study of brain functions, the blood oxygenation level dependent (BOLD) effect
is incompletely understood. Particularly, negative BOLD responses(NBRs) is
controversial. This paper presents a new fMRI data analysis method, which is
more accurate than the typical conventional method. The authors conducted the
experiments of simple repetition, and analyzed the data by the new method. The
results strongly suggest that the deactivations(NBRs) detected by the new
method are the deactivations of interneurons, because the deactivation ratios
obtained by the new method approximately equals the deactivation ratios of
interneurons obtained by the study of interneurons. The (de)activations
detected by the new method are largely different from those detected by the
conventional method. The new method is more accurate than the conventional
method, and therefore the (de)activations detected by the new method may be
correct and the (de)activations detected by the conventional method may be
incorrect. A large portion of the deactivations of inhibitory interneurons is
also considered to be activations. Therefore, the right-tailed t-test, which is
usually performed in the conventional method, does not detect the whole
activation, because the right-tailed t-test only detects the activations of
excitatory neurons, and neglect the deactivations of inhibitory interneurons. A
lot of fMRI studies so far by the conventional method should be re-examined by
the new method, and many results obtained so far will be modified.
