Cross-modal cue effects in psychophysics, fMRI, and MEG in motion perception
Hanada, Grant Masata
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Motion perception is critical to navigation within the environment and has been studied primarily in the unisensory visual domain. However, the real world is not unisensory, but contains motion information from several modalities. With the billions of sensory stimuli our brains receive every second, many complex processes must be executed in order to properly filter relevant motion related information. In transparent motion, when there are more than one velocity fields within the same visual space, our brains must be able to separate out conflicting forms of motion utilizing environmental cues. But even in unimodal visual situations, one often uses information from other modalities for guidance. We studied this phenomenon in psychophysics with cross-modal (visual and auditory) cues and their role in detecting transparent motion. To further examine these ideas, using a single subject we explored the spatiotemporal characteristics of the neural substrates involved in utilizing these different cues in motion detection during magnetoencephalography (MEG). Another dimension of motion perception is involved when the observer is moving and, therefore, must deal with self-motion and changing environmental cues. To better understand this idea we used a visual search psychophysical task that has been well studied in our lab to determine whether subjects use a simple relative-motion computation to detect moving objects during self-motion or whether they utilize scene context when detecting object motion and how this might change when given a cross-modal auditory cue. To find the spatiotemporal neural characteristics involved in this process, functional magnetic resonance imaging (fMRI) and MEG were performed separately in elderly subjects (healthy and a stroke patient) and compared with previous studies of young healthy subjects doing the same task.
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