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Faculty List
Shinsuke Shimojo
sshimojo@cns.caltech.edu
Ph.D., 1985, Massachusetts Institute of Technology
Psychological and Behavioral Studies of Perception Attention and Cognition in the Human
Sensory signals flow into our nervous system constantly and their very number is overwhelming to consider. Moreover, sensory signals usually are ambiguous in their correspondence to real-world physical events. Yet, our brain somehow enables us to perceive objects and respond to them adaptively. This simple fact already indicates the existence in the brain of massive, efficient, and adaptive neural computation with various real-world constraints cleverly implemented in it. But how is such processing accomplished?
Research activity in the Shimojo laboratory has been devoted to tackling this challenging problem from experimental/psychobiological viewpoints. In particular, we are conducting psychophysical and behavioral studies of higher-order visual perception, spatial attention, integration across different sensory modalities, and sensory-motor functions.
Our latest discovery of a novel visual illusion, the "line motion" effect, would be a perfect example. In this paradigm, we draw the observer's attention to a particular location in the visual field, either by a visual cue or by a task demand. Then, we present a line segment between the attended and the unattended locations. Even though the line probe is presented all at once as a single unit, the line appears to unfold or expand from the attended to the unattended location, thus reflecting an attention-modulated efficiency gradient in visual information processing across the visual field. This new psychophysical technique has turned out to be sensitive to various types of spatial attention, such as auditory- and somatosensory- as well as visually-driven, voluntary, task-demanded, memory-based and attention related to motor programming.
Employing yet another visual effect which was also discovered in our laboratory (the "spoke" illusion), we have examined the trade-off between the complexity of visual surface formation and the temporal resolution of visual processing. The results suggest that each of the multiple representations of space in the brain has its own role and specific temporal resolution in visual surface formation, and that these multiple resolutions could be directly reflected in our conscious experience of visual motion perception.
Other on-going projects in our laboratory cover topics such as eye movements as an indicator for internal representation of space, reaction times in various sensory modalities, and stability and constancy of the perceptual world. We are currently preparing to extend our research scope to sensory-motor development in the human infant, and transcranial magnetic stimulation of cortices in the normal adult's brain.
Different ways of defining a triangle for neural encoding. Top: Luminance-defined edges. Center: Illusory contours. Bottom: Illusory contours with color filling-in and transparency perception. They show different temporal properties when they are used for apparent motion.
