Vision and Audition
Beginner neuroscientists will often start with shedding light on perception. After all, sensation and perception are the steps preceding interpretation. While human are generally believed to possess a total of five sense, only two will be discussed in the present short entry.
The parallels between audition and vision lie in the trajectory undertaken by the sensory stimuli. Waves (whether light or sound) first encounter the receptors, then the respective carrying nerves. In the case of vision, the receptors are the rods and cones located on the retina (the lining at the back of the eye. In the case of auditory cells, these are hair cells or stereocilia, inner and outer. The transmitting nerves in question are the optic nerve for vision, and the auditory nerve for audition.
Interestingly, a blind spot is formed at the exact location where the optic nerve leaves the eye. Also, the signal then travels to the thalamus, sometimes called the relay station of the brain, where it is further adjourned to the visual cortex at the back of the cranium, or the occipital lobe. The temporal lobe is most often associated with hearing.
An artificial blue eye. Albino eyes are red or purple because of a complete lack of melanin. Eye color is believed to be largely due to genetics (e.g. recessive [blue, green, hazel] and dominant [brown] alleles). However, researchers in Australia have challenged that notion as too simplistic. Also, while eye color is permanent, companies such as Lumineyes claim that they can change the amount of melanin, and thus the coloring, of human eyes. Is it safe? Image: Copyright © Megan Jorgensen