Part of Brain Telling Eyes What To Look For

As I was walking around the AOA’s exhibit hall on Thursday, I heard the faint voice of a book calling out … “Buy meBuy me“.  Having vowed not to buy anything at the meeting, I placed the attractive volume back on the table, despite the salesman’s urging.  “Do you really want me to pack this up and take it back with me?”

Skalicky Cover

I didn’t buy the book, deciding to take a trip back through the exhibit hall the next day and sure enough the book leaped off the table into my hands.  I thumbed through it again.  From its Preface:   “Ocular and Visual Physiology is a textbook for ophthalmologists, optometrists, orthoptists, and visual neuroscientists throughout the world, in training and beyond … Without a thorough understanding of this subject, clinicians and visual neuroscientists cannot achieve their desired level of competency.”

Captivated by the sound bites in Chapter 13 on the Lateral Geniculate Nucleus (LGN), I succumbed.  Consider the following:

Skalicky - LGN

Interesting, but the data about projections to and from the LGN really caught my eye.  Retinal projections to the LGN comprise only 10-20% of LGN inputs.  Extraretinal projections to the LGN constitute 80-90% of the LGN inputs!  These inputs come from primary visual cortex; extrastriate visual cortex; superior colliculus; pretectal area; and thalamic reticular nuclei to modulate the flow of information from LGN to the primary visual cortex – which is the target for much of the axonal output from the LGN, although some terminate in the extrastriate cortex which may help account for so-called blindsight.  Visual attention is heavily modulated by the superior colliculus and pulvinar.

I wouldn’t recommend that you rush out and buy this book, but it is an excellent reminder of how many visual processes in the brain occur through pathways other than retina to LGN.

5 thoughts on “Part of Brain Telling Eyes What To Look For

  1. As a profession, we worship the retina, even though according to the vote of the neurons only 10 to 20 percent of seeing is retinally determined. Maybe that’s why we don’t see people growing twice as large when the distance to them is cut in half. Maybe that is why quarters remain quarters rather morphing into circles, lines, and ellipses depending on perspective. Maybe that is why the world returns to normal after we learn to live with our new distorting lenses. Maybe that is why we can’t always predict what patients will like based on our autorefractors. Fortunately, eye doctors don’t need to concern themselves with the other 80 percent of seeing. That only becomes necessary when we move from eyes to vision.

  2. YEP, so why is Lenscrafters allowed to advertise on TV, “our eye exam is the most accurate.” I for one like the brain over the retina hence Charles Bonett Sydrome trumps the retina. Anyway our AOA should put a stop to the Bob Hope kind of TV ads in the same manner we did in that day.

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