Remember the story of Phineas Gage? He was the poor soul who had been working on
ID: 175592 • Letter: R
Question
Remember the story of Phineas Gage? He was the poor soul who had been working on the railroad in 1848 when an explosion caused an iron rod to be driven through the frontal lobes of his brain. Amazingly, Gage survived the accident and became a scientific wonder to scientists and the public around the world. Let's imagine for a moment a few scenarios involving Mr. Gage.
7)
If the iron rod that pierced Gage's brain severed only his left optic tract, which parts of Gage's visual field would be lost? Check ALL that apply.
(0.3pts)
left lateral visual field
left medial visual field
right lateral visual field
right medial visual field
8)
If the iron rod that pierced Gage's brain severed Gage's optic chiasm directly down the middle, which parts of his visual field would be lost? Check ALL that apply.
(0.3pts)
left lateral visual field
left medial visual field
right lateral visual field
right medial visual field
Explanation / Answer
7). right lateral visual field
right medial visual field
Optic nerve is formed by the axons of ganglionic cells, which leaves the eye through optic disk. Optic nerves transmit the sensations to the brain. The medial fibres (of optic nerves) of both sides cross at optic chiasma, which is present near the center of the base of cerebral cortex.
The tracts formed by these medial fibres are called as optic tracts, which synapse with the neurons in the “lateral geniculate body” of the thalamus. The axons of lateral geniculate body form the optic radiation, and this terminates in the visual cortex present in the occipital lobe.
So, from the optic chiasma, the impulses are carried by optic tract to visual cortex present in the occipital lobe of the brain, where the image is perceived. So, the visual sensations from the left side of both eyes are transmitted to the right side of the brain, and visual sensations from the right side of both the eyes are transmitted to the left side of the brain.