Solving Sight: Article #1 - The Brain-Eye Connection: How We See and Perceive the World

Now that we’ve talked about the basic anatomy and structure of the brain, let’s move onto something more specific- vision! Throughout this 3- part series, I will be unpacking everything about the connection between the eye and the brain! As you may know, from Article #2, we talked about the occipital lobe, the lobe of your brain used mainly for sight! However, it’s important to note that while the occipital lobe is used mainly for sight, it specializes in visual processing rather than vision. So take what you’ve learned from Article #2, keep it on hand, and now get ready to learn about all things sight! 

Vision is a deeply complex process that involves a sophisticated partnership between the eyes and the brain. This collaboration enables us not only to perceive light and color but also to recognize faces, track motion, and navigate the world. Let’s take a look at how this system works, and the many systems that allow us to see!

Anatomy of Vision: Rods, Cones, and Ganglion Cells

At the heart of the visual system are specialized cells in the retina: rods and cones.

Rods: Enable us to see black and white and work in dim light for night vision 

Cones: Enable us to see color and work in bright light for color vision

When light hits these photoreceptors, it triggers a process called phototransduction—a conversion of light into electrical signals that the brain can understand. This affects how neurotransmitters (which we learned about in Article #3!) are released and how messages are sent to neighboring neurons.

These signals are then collected by ganglion cells, which transmit visual information to the brain. Ganglion cells have receptive fields—areas of the retina where light must fall to activate the cell. These fields come in different types:

• On-center/off-surround cells fire most when light hits the center of the field and the surroundings remain dark.

• Off-center/on-surround cells do the opposite—they fire more when light is in the surrounding area but not the center.

  

  An example in more detail is here!

  
  

There are two main types of ganglion cells:

• P (parvocellular) cells: small, sensitive to color and fine detail.

• M (magnocellular) cells: large, detect motion and low contrast.

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These cells project to different layers in the brain:

• Parvocellular layers (3–6) of the thalamus receive input from P cells.

• Magnocellular layers (1–2) receive input from M cells.

Visual Processing in the Brain

Visual information travels from the retina to the thalamus, a relay station that adds information before sending signals to the primary visual cortex (V1). At the optic chiasm, information from each visual field crosses over to the opposite side of the brain.

From V1, visual data splits into two major streams:

1. The Dorsal Stream – “Where” and “How”

This pathway processes motion and spatial location. It includes:

• Magnocellular layers → V1 (primary visual cortex), V2 (processes visual information), V3 (visual processing), V5 (medial temporal lobe)

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2. The Ventral Stream – “What”

This stream helps with object recognition and color processing. It includes:

• Parvocellular layers → V1, V2 ,V4 (object recognition) → inferior temporal lobe

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Conclusion

Our ability to see isn’t just a function of the eyes—it's a deeply rooted collaboration between photoreceptors, ganglion cells, the thalamus, and the visual cortex. This connection not only sheds light on how we perceive the world but also helps us diagnose and treat a wide range of visual and neurological conditions. Whether it’s recognizing your friend’s face or maybe even reading a book, your brain and eyes work together, constantly communicating. Thank you so much for tuning into today’s article explaining the basics of sight! If this topic interests you, make sure to tune in for our next article which will talk about blindness and other eye-related disorders! As always, here is the annual neuroscience pun: 

Q: Why were the two retinas such good friends?

 A:“They always saw eye to eye”.