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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, such as a short video clip shot during a stroll on a forest trail."

The bird enthusiast who chronicled the adventures of a flock of red-headed conures in his book The Wild Parrots of Telegraph Hill knows most of the parrots by name, proving that we can become acutely attuned to our dayto- day environment. While it makes perfect sense that we are best at discriminating the facial features that are typical of our neighbors, how our brains achieve this feat has been less clear.

Neurons in the primary visual cortex only respond when a stimulus appears within a window covering a small part of the visual field that the eye sees. This window is known as the neuron's "receptive field." Whenever a stimulus enters the neuron's receptive field, the cell produces a volley of electrical spikes, known as "action potentials," which can be recorded.

But these neurons don't react to just anything. Instead they are highly specialized and can only "see" a single attribute such as color, motion, or a specific luminance pattern. By measuring a certain neuron's action potentials in response to random visual stimuli, researchers can infer the profile of its receptive field. But growing evidence hints that this simple picture is incomplete. The response of individual neurons can be strongly influenced by simple stimuli in the surround of the receptive field, a phenomenon known as contextual modulation.

To unveil how contextual modulation shapes the apparent profile of neurons, Sharpee and her collaborators presented neurons specialized in recognizing luminance patterns with different sets of visual stimuli, ranging from random noise patterns, such as TV static, to fully natural clips of short walks through a forest, and recorded their action potentials. When she applied information theory to extract meaning from the resulting cacophony of signals, the neurons' responses revealed that brain cells processing visual information adjust their filtering properties to make the most sense of incoming information.

Context is an important part of how we perceive visual stimuli, and Sharpee's results show how individual neurons might adjust their properties in different natural environments, such as on a beach or when trying to identify an individual conure within a flock of fluttering birds.

Lab Photo

Left to right:
Adam Calhoun, Yuan (Sophie) Liu, James Jeanne, Tanya Sharpee, Ryan Rowenkamp, Jeff Fitzgerald, and Minjoon Kouh

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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.

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