The role of gap junction coupling in adjusting the information-gathering properties of neural networks
The nervous system has an impressive ability to self-adjust – as it moves from one environment to another, it can adjust its information processing to accomodate the new conditions. These adjustments are critical to our functioning, but the neural mechanisms that underlie them are not well-understood. How is it that a network can change its processing on the fly?
We studied the neural mechanisms that underlie one of the most well-known behavioral adjustments, the shift in visual integration time that occurs as an animal moves from a day to a night environment. Interestingly, we found that this shift is accomplished by the coupling and uncoupling of gap junctions among horizontal cells in the retina. In the night condition, strong coupling between horizontal cells acted as a shunt, which essentially inactivates these cells. This work demonstrated a novel mechanism that allows a network to change the activity of one of its cell classes, and shift its behavior from one state to another. Related Papers
Breakdown of symmetry in the ON and OFF pathways in the retina
The visual system divides the world into two pathways, one that responds to increments of light (ON) and one that responds to decrements (OFF). Traditionally, these pathways have been thought as been “equal and opposite” channels of information - that they respond to similar features of the visual scene, just with opposite polarity. Evidence has gradually accumulated that the two pathways contain differences, both at the physiological and perceptual levels. However, the purpose of these differences – and their functional role in vision – has yet to be described.
We studied the adjustment of these two pathways to day and night conditions. Surprisingly, the ON and OFF pathways make asymmetric adjustments with the change from day to a night environment. We show that these asymmetries correspond to differences in the physical world, specifically, to asymmetries in the detection of increments and decrements that arise at low light levels. The findings demonstrate an example of the nervous system adapting its processing to a constraint imposed by the natural world. The results also have implications for models of downstream processing (e.g. models for higher visual areas, such as LGN or visual cortex). Related Papers
As an undergraduate in the Surface Sciences Laboratory under Dr. Bob Nemanich, I used Conductive Atomic Force Microscopy (C-AFM) to understand the current-voltage characteristics of Schottky Contacts (potential barriers formed at the interface between metals and semiconductors). Related Papers
Cornell University, 2003-2005: I thoroughly enjoyed being a lab instructor for several circuits, microelectronics, and embedded systems classes in the Department of Electrical and Computer Engineering at Cornell Unversity:
North Carolina State University, 2001-2002: I also taught a laboratory class in the Department of Computer Science at NC State: