Lobes and Vision: There's More to it than Meets the Eye
The brain is made up of lobes. The lobes perform different functions.
Here’s a summary of the basic functions performed by each lobe.
If you’re like me, the text included with the diagram suggests that the Occipital Lobe is solely responsible for vision.
After all, the summary for the Frontal Lobe doesn’t say anything about vision. (It says “movement” but it doesn’t say “eye movement.”)
Until recently I thought raw data was—with a few detours or stops along the way—routed from the eyes to the Occipital Lobe and that was the whole visual system.
It seemed to make sense when you looked at the “wiring diagram” of the optic nerves and radiations.
But, as I found out, there’s a lot more to it.
The visual system has quite a few “parts” and processes. It isn’t just the eye “seeing” and the Occipital Lobe processing raw data.
A key part of the visual system is the way the eye obtains that raw data. I’m not going to go into detail about all the components. But I am going to talk about one of them because it’s frequently implicated in mTBI cases.
The part I’m talking about facilitates data acquisition is voluntary eye movements. It’s called the Frontal Eye Field (FEF). It’s located within the Frontal Lobe. It plays a crucial role in controlling voluntary eye movements.
This diagram shows where the FEF (and other Eye Fields) are located.
Injury to the FEF (or its connections to the other parts of the brain) disrupts the saccades needed for reading. An injury to the FEF causes difficulty shifting between lines of text. It produces slower reading speeds, more word errors (identifying the wrong word) and decreased comprehension.
This is an example of what eye movements look like after when saccades are affected by an mTBI.
Mild traumatic brain injuries (definitionally) don’t show up in imaging. But there’s strong objective evidence (e.g., testing that follows the eyes during reading) that establishes or corroborates the nature of the brain injury.
As some would say, the eyes (or the ayes) have it.