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specialized in detecting fine detail and colors. The 5 million or so cones in each eye enable us to
see in color, but they operate best in bright light. The cones are located primarily in and around
the fovea, which is the central point of the retina.
To demonstrate the difference between rods and cones in attention to detail, choose a word in
this text and focus on it. Do you notice that the words a few inches to the side seem more
blurred? This is because the word you are focusing on strikes the detail-oriented cones, while the
words surrounding it strike the less-detail-oriented rods, which are located on the periphery.
As you can see in Figure 4.11 "Pathway of Visual Images Through the Thalamus and Into the
Visual Cortex", the sensory information received by the retina is relayed through the thalamus to
corresponding areas in the visual cortex, which is located in the occipital lobe at the back of the
brain. Although the principle of contralateral control might lead you to expect that the left eye
would send information to the right brain hemisphere and vice versa, nature is smarter than that.
In fact, the left and right eyes each send information to both the left and the right hemisphere,
and the visual cortex processes each of the cues separately and in parallel. This is an adaptational
advantage to an organism that loses sight in one eye, because even if only one eye is functional,
both hemispheres will still receive input from it.