Once the photopigment in the cone absorbs light, it undergoes a change in shape, activating a G-protein called transducin. This activation leads to a decrease in the concentration of cyclic GMP (cGMP) inside the cell, causing cGMP-gated ion channels to close. The closure of these channels results in hyperpolarization of the cone cell, reducing the release of the neurotransmitter glutamate. This change in neurotransmitter release is detected by bipolar cells, which then transmit the signal to ganglion cells and, ultimately, to the visual cortex of the brain.
