BackgroundAudition provides important cues with regard to stimulus motion although vision may provide the most salient information. It has been reported that a sound of fixed intensity tends to be judged as decreasing in intensity after adaptation to looming visual stimuli or as increasing in intensity after adaptation to receding visual stimuli. This audiovisual interaction in motion aftereffects indicates that there are multimodal contributions to motion perception at early levels of sensory processing. However, there has been no report that sounds can induce the perception of visual motion.Methodology/Principal FindingsA visual stimulus blinking at a fixed location was perceived to be moving laterally when the flash onset was synchronized to an alternating left-right sound source. This illusory visual motion was strengthened with an increasing retinal eccentricity (2.5 deg to 20 deg) and occurred more frequently when the onsets of the audio and visual stimuli were synchronized.Conclusions/SignificanceWe clearly demonstrated that the alternation of sound location induces illusory visual motion when vision cannot provide accurate spatial information. The present findings strongly suggest that the neural representations of auditory and visual motion processing can bias each other, which yields the best estimates of external events in a complementary manner.

BackgroundVision provides the most salient information with regard to stimulus motion, but audition can also provide important cues that affect visual motion perception. Here, we show that sounds containing no motion or positional cues can induce illusory visual motion perception for static visual objects.Methodology/Principal FindingsTwo circles placed side by side were presented in alternation producing apparent motion perception and each onset was accompanied by a tone burst of a specific and unique frequency. After exposure to this visual apparent motion with tones for a few minutes, the tones became drivers for illusory motion perception. When the flash onset was synchronized to tones of alternating frequencies, a circle blinking at a fixed location was perceived as lateral motion in the same direction as the previously exposed apparent motion. Furthermore, the effect lasted at least for a few days. The effect was well observed at the retinal position that was previously exposed to apparent motion with tone bursts.Conclusions/SignificanceThe present results indicate that strong association between sound sequence and visual motion is easily formed within a short period and that, after forming the association, sounds are able to trigger visual motion perception for a static visual object.

In representational momentum (RM), the final position of a moving target is mislocalized in the direction of motion. Here, the effect of a concurrent sound on visual RM was demonstrated. A visual stimulus moved horizontally and disappeared at unpredictable positions. A complex tone without any motion cues was presented continuously from the beginning of the visual motion. As compared with a silent condition, the RM magnitude increased when the sound lasted longer than and decreased when it did not last as long as the visual motion. However, the RM was unchanged when a brief complex tone was presented before or after the target disappeared (Experiment 2) or when the onset of the long-lasting sound was not synchronized with that of the visual motion (Experiments 3 and 4). These findings suggest that visual motion representation can be modulated by a sound if the visual motion information is firmly associated with the auditory information.

A new species of spionid polychaete, Polydora onagawaensis, is described from mollusk shells in Pacific waters of northeastern Japan. Its nuclear 18S rRNA gene sequence as well as its morphology, reproductive features, life history and infestation characteristics are reported. Polydora onagawaensis sp. nov. belongs to the Polydora ciliata/websteri group and has a moderate size and variable black pigmentation on the palps and body. Up to 115 worms were found boring in a single scallop shell from suspended cultures in Onagawa Bay, with significantly higher numbers in the right than in the left valve. Females repeatedly deposited a string of egg capsules from around October to June (seawater temperature was below 15°C). The larvae developed inside the egg capsules for 2 wk (10°C, laboratory conditions), until the 3-chaetiger stage, before being released as planktonic larvae. The main spawning occurred in December, recruitment onto the shells increased after January, and most large worms disappeared between July and October. Thus, the estimated life span is around 1.5 yr after settlement. Details on biology and gene information not only contribute to distinguishing the species from other polydorids similar in morphology, but also allow control of polydorid infestation in mollusk aquaculture.

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