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Melissa Saenz, Ph.D. Postdoctoral Fellow in Biology, Koch Lab Lecturer in Computation & Neural Systems saenz@caltech.edu office: (626)395-8964 Caltech, MC 216-76 Pasadena CA 91125 New Caltech Course on Brain Plasticity I am pleased to be teaching BI/CNS 286. Here's the course website. How the human brain responds to seeing motion Here's a movie demo of functional MRI responses to visual motion. New Study on Sight Recovery after Blindness Using functional MRI brain scans, we studied brain reorganization in two individuals who became blind in early childhood and partially regained sight decades later as adults in their 40's. Previous studies had shown that the visual cortex in blind people can take on new auditory and tactile functions (cross-modal plasticity), and this brain reorganization may be related to enhanced non-visual abilities in the blind. However, it was not previously known if these non-visual responses would persist if a blind person should someday regain their vision. In our subjects, we found that responses to sound persisted alongside regained visual responses in the visual cortex even many years after sight-recovery. Most interestingly, the auditory responses didn't move in randomly. In sighted people, an area of visual cortex called MT+/V5 has a specialized role in processing moving stimuli. In the sight-recovery subjects, we used visual stimulation to locate MT+ (which is difficult to define based on anatomy alone) and then found that this region also responded specifically to sound motion (i.e. sound coming from a moving source). Thus, the sight-recovery subjects gave us the unique chance to test whether brain plasticity in this area was "functionally relevent", taking advantage of pre-existing specialization for motion processing. Saenz, Lewis, Huth, Fine, Koch (2008) Visual Area MT+ Responds to Auditory Motion in Human Sight-Recovery Subjects. Journal of Neuroscience. [PDF] Press Coverage: Nature News "Re-wired for Sight and Sound" Science News "Sharing Valuable Real Estate" New Scientist "Why blind brains never stop seeing" Caltech Press Release Collaborator Ione Fine at University of Washington Mike May, one of the two sight-recovery subjects This research supported by the Mind Science Foundation. Notes and demos from my talk to the public on Brain Adaptation to Blindness and Sight-Recovery with the Mind Science Foundation in San Antonio, TX). Visual Attention More visual information reaches our eyes than our brains can fully process. Selective attention is one strategy the visual system uses to focus its resources on the most relevent information. As William James wrote "My experience is what I agree to attend to. Only those items which I notice shape my mind - without selective interest, experience is utter chaos." (Principles of Psychology, 1890). Research on this topic confirms that attended items receive improved visual processing, while unattended items can suprisingly escape perception. My experiments used two different techniques to study visual attention. Functional MRI brain scans are used to measure how activity in the human visual system is modulated by where or what an observer is paying attention to in a visual display. These experiments are coupled with visual psychophysics to explore the behavioral effects of attention. My experiments tested the hypothesis that attention to certain elemental visual features (e.g. color, orientation, motion direction) enhances neuronal responses to items composed of the attended feature throughout the visual scene. For example, this hypothesis predicts that when an observer searches a shelf for a red book, attention would sensitize neurons tuned to the color red with receptive field locations throughout the scene. This idea stresses that the neuronal facilitation is spatially global and not restricted to a local region of focus. This type of global mechanism could be useful to the visual system because the location of relevent visual items is not always known in advance. For more info please see publications . |