Describe the visual pathways. Include in your answer cells and layers of the retina and their projections to the thalamus and to cortical areas.

Question

What will be an ideal response?

Answer 1

When light hits the back of the eye, it is absorbed by the photopigments found in the photoreceptors - rods and cones. This reaction converts the light energy into a neural impulse. In turn, the photoreceptor decreases its inhibition of the bipolar cells, which sends excitatory signals to the ganglion cells. The axons of the ganglion cells form the optic nerve, which leaves the back of the eye and transmits the visual information to the brain. Axons from the temporal sides of each eye remain on the same-side hemisphere, when axons from the nasal sides of each eye cross at a point called the optic chiasm to the opposite side hemisphere. The axons synapse with the lateral geniculate nucleus of the thalamus for filtering out of unattended visual information. Attended visual information is further taken to the primary visual cortex (V1), where initial processing and awareness occur. This information is then further sent to two main pathways. One is the ventral pathway, which goes from the occipital lobe to the temporal lobe for identification of objects and faces. The second is the dorsal pathway, which goes from the occipital lobe to the parietal lobe for depth perception and to determine where in space objects are located. Information from both pathways then synapses in the frontal lobe.