In the generation of the b-wave, which cells depolarize alongside bipolar cells?

• A. Photoreceptors
• B. Retinal ganglion cells
• C. Glial cells
• D. Bipolar cells and Müller cells

Answer: (D)

The b-wave in an electroretinogram reflects activity in the inner retina when light activates the ON pathway. The ON-bipolar cells depolarize in response to light (glutamate release from photoreceptors decreases, which disinhibits these cells). Müller glial cells also respond to the resulting shifts in extracellular ions, especially potassium, and their currents contribute to the overall positive deflection recorded as the b-wave. So, both bipolar cells and Müller cells depolarize together to produce this wave. Photoreceptors drive the a-wave through hyperpolarization, retinal ganglion cells aren’t the main source of the b-wave, and general glial cells aren’t specifically implicated beyond the Müller cells in this context.