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Steven Hsiao Ph.D

Professor of Neuroscience

Telephone Number: 410-516-6409
Fax Number: 410-516-8648
Johns Hopkins University
Mind/Brain Institute
3400 North Charles St.
Baltimore, MD 21218
Room: Brain/ Krieger 373

Neurophysiology of the Central Nervous System

The broad aim of my research is to understand the neural mechanisms of tactile perception and to develop methods for providing sensory feedback to patients with upper limb prothetics.   Our goal is to understand how spatial form, texture, motion, complex vibrations and three dimensional objects (stereognosis) represented and transformed in the neural pathways leading to tactile perception.  We have found that the neural mechanisms of orientation, motion and curvature are processed in areas 3b, 1 and 2 of primary somatosensory cortex and that the underlying mechanisms for these aspects of perception are analogous between touch and vision.  The mechanisms for 3D object preception appear to be different between touch and vision and in touch involve integrating cutaneous inputs with proprioceptive inputs.  

We use our knowledge about the underlying coding mechanisms to stimulate the somatosensory cortex in trained animals. Our goal is to provide patterned inputs to the cortex and allow the animals to perceive complex shape. The outcome from these studies will allow us to understand how to proved provide sensory feedback of complex objects.

Our etudies on tactile attention are based on two different hypothesis. One is that attention is broadly tuned and nonspecific. If this is the case, then attention should function as a kind of neural "spotlight" that simply directs the animals efforts within the somatosensory system from one location on the body to another. The most likely role that attention plays under these circumstances is to enhance the responses of neurons that fall within the "spotlight".  Another more likely possibility is that attention is highly specific and functions to tailor the neural responses in a way that allows the animal to achieve a specific perceptual goal. For example, if the animal is performing an orientation discrimination task then only those neurons that are orientation selective will show attention modulated responses and other neurons that lie near those neurons but are not critical for performing the task will not be affected. To test these alternative hypothesis and to understand the role that attention plays in tactile processing in primary (SI) and secondary (SII) cortex, we perform experiments on animals trained to perform a variety of attention tasks. We find that attention effect on neurons is highly feature specific and increases both the gain of the neurons and the degree of synchronous firing between neurons.  We hypothesize that spike synchrony plays a major role in sensory processing.