Retinal Direction Selectivity… Reversed!!!
In a recent paper, “Visual Stimulation Reverses the Directional Preference of Direction-Selective Retinal Ganglion Cells” (2012), the lab of Dr. Marla Feller demonstrated direction reversal of a subgroup of Direction Selective Ganglion Cells in the mouse retina. The finding is contrary to the predominant dogma that direction selectivity is endowed by circuity that is hard-wired. Direction Selectivity refers to the cells propensity to fire more spikes in response to moving stimuli in one direction over the opposite direction, and has been a popular sub-field of retina research.
In this study, the lab uses moving gratings of various angles with simultaneous loose patch recordings to probe the direction selectivity of the ganglion cells. Surprisingly, a simple two minutes of moving grating stimulus was enough to cause roughly a third to a half of the cells to reverse their preferred stimulus direction. The reversals are robust and are maintained throughout the duration of the loose patch recording (up to 20 minutes).
To begin to address the mechanism, the study used whole cell voltage clamp recordings to show that changes in the balance of inhibitory and excitatory currents also occur. Additionally, the response properties of the cell with respect to stimulus phase also exhibited drastic changes after the direction reversal occurred. These two findings point to not only a change in synaptic strength of the original circuit, but also the potential recruitment of different circuitry.
The following excerpt from their paper is a nice summary of the broader impact of the study:
“The significance of these findings comes in the observation that dynamic circuit interaction can overcome an anatomical bias and change the ultimate computation performed by a neuronal circuit.”
Dr. Marla Feller‘s lab is at the University of California, Berkeley. In addition to direction selectivity, the lab studies retinal development, with a specific interest in the waves of activity that occur during development. Please join us on Tuesday, January 29, 2013, at 4:00pm in the Large Conference Room of the Center for Neural Circuits & Behavior for Dr. Feller’s talk, “Development of functional circuits in the retina.”
Alex K. Heitman is a second-year student in the lab of E.J. Chichilnisky, also working on the retina!
Rivlin-Etzion M., Wei W. & Feller M. (2012). Visual Stimulation Reverses the Directional Preference of Direction-Selective Retinal Ganglion Cells, Neuron, 76 (3) 518-525. DOI: 10.1016/j.neuron.2012.08.041