Are OFF-center bipolar cells depolarized or hyperpolarized in the light?

OFF-center bipolar cells are hyperpolarized in the presence of light due to the way they respond to changes in photoreceptor activation. When light hits the photoreceptors, such as rods and cones, it initiates a phototransduction cascade that leads to the hyperpolarization of these photoreceptors. This decrease in glutamate release from the photoreceptors occurs because light inhibits the photoreceptors' activity.

OFF-center bipolar cells, which are activated by the presence of glutamate, respond to the reduction of glutamate when the photoreceptors are hyperpolarized. Since OFF-center bipolar cells have ionotropic receptors (specifically AMPA receptors) that mediate a depolarization of the cell in the presence of glutamate, the reduction or absence of this neurotransmitter leads to hyperpolarization of the OFF-center bipolar cells.

Thus, when light is present, these bipolar cells do not receive the excitatory input they need, resulting in their hyperpolarization and decreased activity. This mechanism is essential for the processing of visual information, as it allows for the differentiation of light and dark stimuli in the visual field.