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In present study, we mainly investigated whether multisensory interaction of
audiovisual stimuli presented on the central and peripheral spatial locations was con-
sistent. In order to gain maximal difference of audiovisual interaction between on the
central and peripheral spatial locations, we conducted a pre-experiment prior to all
experiments and determined the eccentricity of peripheral spatial location on where
stimuli were presented.
2 Method
2.1 Subjects
Thirteen volunteers (22 to 31 years, mean: 24.8 years, both males), students from the
Kagawa University participated in the experiment. All had normal or corrected-to-
normal vision and normal hearing and all were right handed. The experimental proto-
col was approved by the ethics committee of Kagawa University. After receiving a
full explanation of the purpose and risks of the research, subjects provided written
informed consent for all studies as per the protocol approved by the institutional re-
search review board.
2.2 Stimuli
The experiment contained three stimulus types which are unimodal visual (V) stimuli,
unimodal auditory (A) stimuli, and multimodal audiovisual (VA) stimuli. Each type
had two subtypes of standard stimuli and target stimuli.
The unimodal V standard stimulus was a white, horizontal, square wave grating
(subtending a visual angle of approximately 3°). The unimodal A standard stimulus
was of a 1600 Hz tone with linear rise and fall times of 5ms and an intensity of 65 dB.
The multimodal VA standard stimulus consisted of the simultaneous presentation of
both unimodal A and V standard stimuli at a spatially congruent location. The dura-
tion of each type of stimulus was 105 ms.
The unimodal V and A target stimuli were very similar to the unimodal V and A
standard stimuli, but contained a distance of no stimulation exhibition time half way
through the standard stimuli which subjectively made the stimulus appear to flicker
(V target stimulus) or stutter (A target stimulus). The difficulty of the target stimulus
detection can be adjusted for each subject during a training session prior to the ex-
periment by selecting the different distance of no stimulation exhibition time halfway
so that the accuracy in detecting the target stimuli was 80%. The V target stimulus
contained four different distances of no stimulation exhibition time halfway which
were 25ms, 35ms, 45ms, and 55ms. The A target stimulus also contained four differ-
ent distances of no stimulation exhibition time halfway which were 15ms, 25ms,
35ms and 45ms. The multimodal VA target stimulus consisted of the simultaneous
presentation of both unimodal A and V target stimuli at a spatially congruent location.
The visual detection capability was degressive with the increase of the eccentricity of
presented location. We conducted a pre-experiment prior to all experiments, in order
to determine the max eccentricity of peripheral spatial location on where stimuli were
presented. The pre-experiment contained 320 V standard stimuli and 320 V target
stimuli. The V standard and target stimuli were presented with equal probability at an
