The Eye and Visual Pathways

Light Regulation

• Iris opens and closes the pupil – Allows light in– Protects eye from

light damage• Reflex• Light is then focused

by the lens

Retina and Photoreceptors

• Rods – more numerous, functions in dim light• Cones – color vision, found in the fovea

– 3 types – red, blue, & green

• Ganglion cells carry information to the optic nerve

Blindspot

The Human Eye

Cornea

Iris

Iris

Lens

Pupil

Vitreous Gel

Optic Nerve

Retina

Macula

Fovea

Visual Pathway • Right visual field is processed in the left hemisphere

• Medial retina crosses at the optic chiasm, lateral does not

• Info goes thru the thalamus– Most goes thru the

lateral geniculate nucleus

– Some first goes through the superior colliculus

Visual Processing• Message first goes to the occipital cortex• Dorsal – ‘where’ pathway

– Ends in parietal lobe

• Ventral – ‘what’ pathway– Ends in the temporal lobe– Color, shape, facial recognition