Visual Processing in the Retina and Brain

Photoreceptors

Rods and cones hyperpolarize in response to light.

Bipolar cells

Respond with graded potentials and can be either ON or OFF types.

Horizontal cells

Mediate lateral inhibition to enhance contrast.

Amacrine cells

Modulate signal transmission, often affecting ganglion cell responses.

Ganglion cells

Generate action potentials that convey visual information to the brain.

Rod photoreceptors

Approximately 120 million in the human retina.

Cone photoreceptors

Approximately 6 million in the human retina.

Pathway from photoreceptors to ganglion cells

Rods and cones synapse onto bipolar cells, which synapse onto retinal ganglion cells.

On-center ganglion cells

Activated when light is in the center of their receptive field and inhibited when light is in the surround.

Off-center ganglion cells

Show the opposite response to On-center cells.

Ganglion cells and visual contrast

Respond more strongly to differences in light intensity (contrast) rather than uniform illumination.

Hermann-Hering grid illusion

Shows gray spots at the intersections of a white grid on a black background due to lateral inhibition in retinal ganglion cells.

Optic nerve

Carries signals from the retina to the brain.

Optic chiasm

Where optic nerve fibers partially cross.

Optic tract

Carries information from the chiasm to the lateral geniculate nucleus (LGN).

Optic radiation

Transmits signals from the LGN to the visual cortex.

Primary visual cortex

Responsible for the initial processing of visual information.

Area V1

Another term for the primary visual cortex.

Striate cortex

Another term for the primary visual cortex.

Brodmann's area 17

Another term for the primary visual cortex.

Column in the visual cortex

A vertically organized group of neurons that responds to specific stimulus properties, such as orientation or eye dominance.

Where pathway

Processes motion and spatial location in the parietal lobe.

What pathway

Processes object recognition in the temporal lobe.

Border ownership cells

Respond to edges belonging to a specific object and are found in area V2 of the visual cortex.