The Shimojo Psychophysics Laboratory is one of the few laboratories on the campus of the Caltech which exclusively concentrates on the study of perception, cognition, and action in humans. The lab employs psychophysical paradigms and a variety of recording techniques such as eye-tracking, functional magnetic resonance imaging (fMRI), electroencephalogram (EEG), as well as, brain stimulation techniques such as transcranial magnetic stimulation (TMS), transcranial direct current stimulation (tDCS), and recently ultrasound neuromodulation (UNM). They try to bridge the gap between cognitive and neurosciences. They would like to understand how the brain adapts real-world constraints to resolve perceptual ambiguity and to reach ecologically valid, unique solutions. In addition to their continuing interest in surface representation, motion perception, attention, and action, they also focus on crossmodal integration (including VR environments), visual preference/attractiveness decision, social brain, flow and choke in the game-playing brains and individual differences related to "neural, dynamic fingerprint" of the brain.

Dr. Li received his medical degree in 1997 from Zhejiang University School of Medicine in China and his Ph.D. in Neuroscience in 2003 from the University of Texas at Houston where he studied the organization of reciprocal feedback synapse at the axon terminal of the retinal bipolar cell in Dr. Stephen Massey's laboratory. From 2003 to 2007, as a postdoctoral fellow, he worked with Dr. Steven DeVries at Northwestern University where he investigated synaptic connections between photoreceptors and bipolar neurons in a mammalian retina. Dr. Li joined NEI as the principal investigator of the Unit on Retinal Neurophysiology in 2007. His unit uses a variety of physiological and anatomical techniques to explore retinal synapses and circuits and their functions in vision.

The long-term goal of our research is to study the mammalian retina as a model for the central nervous system (CNS) -- to understand how it functions in physiological conditions, how it is formed, how it breaks down in pathological conditions, and how it can be repaired. We have focused on two research themes: 1) Photoreceptor structure, synapse, circuits, and development, 2) Hibernation and metabolic adaptations in the retina and beyond. As the first neuron of the visual system, photoreceptors are vital for photoreception and transmission of visual signals. We are particularly interested in cone photoreceptors, as they mediate our daylight vision with high resolution color information. Diseases affecting cone photoreceptors compromise visual functions in the central macular area of the human retina and are thus most detrimental to our vision. However, because cones are much less abundant compared to rods in most mammals, they are less well studied. We have used the ground squirrel (GS) as a model system to study cone vision, taking advantage of their unique cone-dominant retina. In particular, we have focused on short-wavelength sensitive cones (S-cones), which are not only essential for color vision, but are also an important origin of signals for biological rhythm, mood and cognitive functions, and the growth of the eye during development. We are studying critical cone synaptic structures – synaptic ribbons, the synaptic connections of S-cones, and the development of S-cones with regard to their specific connections. These works will provide knowledge of normal retinal development and function, which can also be extended to the rest of CNS. In addition, such knowledge will benefit the development of optimal therapeutic strategies for regeneration and repair in cases of retinal degenerative disease. Many neurodegenerative diseases, including retinal diseases, are rooted in metabolic stress in neurons and/or glial cells. Using the same GS model, we aim to learn from this hibernating mammal, which possesses an amazing capability to adapt to the extreme metabolic conditions during hibernation. By exploring the mechanisms of such adaptation, we hope to discover novel therapeutic tactics for neurodegenerative diseases.

The research in our laboratory focuses on computational and psychophysical studies of visual perception. Unlike machine vision approaches, we emphasize physiological plausibility of our models because such models have more explanatory and predictive power for understanding biological vision. We have been constructing binocular vision models by analyzing known spatiotemporal receptive-field properties of binocular cells in the visual cortex, and have been applying our models to explain depth perception from horizontal disparity (stereovision), vertical disparity (the induced effect), inter-ocular time delay (the Pulfrich effects), motion field (structure-from-motion), and monocular occlusion (da Vinci stereopsis). We also test new predictions from our models via visual psychophysical experiments. A recent emphasis of our research is psychophysical investigation of faces. Face perception is essential for social interactions. While traditional face studies have primarily focused on high-level properties of face perception, we take a complementary approach by investigating contributions of low-level processing along multiple, interactive streams to face perception. We have been studying hierarchical face processing from low to high levels by measuring multi-level adaptation aftereffects. We also plan to conduct computational studies of faces. Finally, we are interested in computational models of motor planning and sensorimotor integration. In particular, we would like to understand synergistic interactions between visual perception and motor control.