How does the brain control eyesight?
What part of the brain controls vision?
The outer layer of the brain consists of four main segments called lobes. The frontal lobe up front, the parietal lobe on top, the temporal lobe along the sides and the occipital lobe pulling up the rear. Most of our senses, thoughts and actions involve at least one of these lobes.
Visual processing starts in retinal cells and continues on to the occipital lobe, a section of the brain near the back of the skull. But processing vision is no simple task, so other parts of the brain have to pitch in, too.
The occipital lobe: The vision center
The occipital lobe is mainly responsible for processing the raw image data sent from the outside world through the eyes.
For that reason, injuries or illnesses that affect the occipital lobe may result in different levels of visual disturbances or even blindness.
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The parietal and temporal lobes: Making sense of what we see
We can’t talk about the occipital lobe without giving a little credit to these two. While the occipital lobe carries most of the visual burden, it’s the parietal and temporal lobes that help us make sense of what we’re seeing.
The parietal lobe plays a big role in visuospatial cognition, our ability to recognize and adapt to the physical space around us. This includes abilities like depth perception, navigation and movement.
When you want to change the channel on TV, you first use the occipital lobe to see the remote. But the parietal lobe’s visuospatial recognition is used to gauge how much distance is between you and the remote — an important detail once you decide to reach for it.
The temporal lobe helps control memory and assign meaning to the images we see. After the occipital lobe registers the image of the TV remote, structures in the temporal lobe help remind us that the remote is used to change the channel, including the knowledge that it should be pointed at the TV and which button to press to get to the channel we’re seeking.
The frontal lobe helps you make decisions and physical movements. While it’s often not considered to be directly involved with vision, some research suggests it might play a role in vision-related tasks after all.
Functional MRIs of the brain show parts of the frontal cortex (part of the frontal lobe) activate during certain vision tests. The tests suggest the frontal cortex keeps your visual focus on the correct object, out of the dozens or more other objects that may be within your field of view at any given moment.
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How the eyes communicate with the brain
When we decide to look at something, parts of the brainstem are called into action. Together with the frontal lobe, they help coordinate eye movements to guide our eye muscles toward the correct stimulus of light (the object we want to look at).
When light enters the eye through the pupil, it travels toward the back of the eye and strikes photoreceptor cells in the retina called rods and cones. Rod cells are responsible for peripheral vision and night vision, while cone cells give you detailed central vision and allow you to see in color.
When light hits its corresponding rod or cone, the cell activates, firing a nerve impulse through the optic nerve — the middleman between the eye and the brain.
This impulse travels through the optic nerve and eventually ends up with the occipital lobe, where it’s processed and perceived as a visible image. This is eyesight.
Since an image isn’t much help without meaning, the occipital lobe sends this visual information to the temporal lobe, where it can be interpreted and formed into a memory.
All of this happens within a fraction of a second, allowing us to perceive the world in essentially real time.
The human brain is a complex web of neurons and synapses. And the more we understand about its ability to process and make sense of random collections of light, the more we can appreciate the equally complex world around us.
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