Page Tools

 

Scientific Report


Scientific Report

Download the Scientific Report [7.5 MB]

View the entry for
Tatyana Sharpee

 

Tatyana Sharpee

Tatyana Sharpee

Assistant Professor
Helen McLoraine Developmental Chair in Neurobiology
Computational Neurobiology Laboratory

"Neurobiologists are on a perennial quest to understand how the brain codes and processes information. In the past, scientists had to rely on simplified objects on a computer screen. I try to take it a step further and analyze how brain cells respond to natural stimuli because some neurons only respond when a certain object comes into view. Scenes from our environment provide a rich ensemble of various object combinations sure to drive any sensory neuron at some point."

Circuits in the nervous system, built from cells and the connections between them, cannot be made as regular as circuits in engineered man-made systems. Yet animals can detect and act on signals in the environment with precision that not only rivals that of engineered systems, but consumes much less energy (the brain is estimated to "run" on 12 Watts of power). Neurons in the retina only respond when a stimulus appears within an approximately round window covering a small part of the visual field that the eye sees. Theoretically, one would expect to obtain the best resolution if these windows, known as receptive fields, were circular and arranged on a perfect triangular lattice. Indeed, receptive fields are roughly circular and are positioned on a roughly triangular lattice, but imprecisely so. In collaboration with Charles Stevens, Sharpee and her team were surprised to find that the combination of these two types of irregularities yielded a near perfect performance. By comparison, performance dropped by a third when receptive fields either were made perfectly circular or irregular receptive fields were adjusted to follow an ideal lattice.

These results suggest new strategies for improving the performance of retinal implants that could help restore vision in blind people. Retinal prosthetic devices rely on an array of electrodes implanted near the retina to send electrical signals to the brain through remaining neurons in the retina. Although the implants themselves are regular arrays, irregularities arise at the interface with the neural tissue, in part because cells can move from their original positions over time. Thus, visual performance of the implant can be reduced when signals derived from a given portion of visual space are sent to cells that normally respond to a somewhat different part of the visual field. The same algorithms that Sharpee and her colleagues used to predict receptive fields in a healthy retina can now be used to find the optimal outlines of the regions of visual space that should be associated with a particular electrode.

Lab Photo

Left to right:
Jeffrey Fitzgerald, Adam Calhoun, Sophie Liu, James Jeanne, Alfred Kaye, Ryan Rowekamp, Tatyana Sharpee, Saeed Saremi

Print version -
Tatyana Sharpee

Faculty

Tatyana Sharpee

Tatyana Sharpee

Assistant Professor
Helen McLoraine Developmental Chair in Neurobiology
Computational Neurobiology Laboratory

Our group works on theoretical principles of how the brain processes information. We are interested in how sensory processing in the brain is shaped by the animal's need to create parsimonious representations of events in the outside world. Our approaches are often derived from methods in statistical physics, mathematics, and information theory.

We also work on methods for analyzing neural data, including methods for analyzing neural responses to natural stimuli, such as a short video clip or sound recording during a stroll on a forest trail. In the past, scientists had to rely on simplified objects on a computer screen or random stimuli to garner information on how the brain processes visual information. Natural stimuli are often much better for probing neural responses than random noise stimuli. Using approaches designed to work with natural stimuli, we hope to achieve a more complete picture of how the brain processes information.

Education

Awards and Honors

Selected Publications

Links

Salk News Releases