Eric and Lisa

The past couple of weeks, Ian and I have been going to the IU Optometry School once a week to help out with research on babies' vision development. Today, Ian had a VEP (Visual Evoked Potential) test done to measure his level of acuity. In the VEP, electrodes were mounted over the visual part of Ian's brain, kind of like an EKG, but attached to the back of his head. He sat in front of a television screen where a pattern of lines was presented. A toy was dangled in front of the television to attract his attention to the center of the screen. The visual evoked potential is the electrical response of the brain to a simple patterned stimuli. The VEP stimulus alternates: the black bars become white, the white bars become black, and the stripes become narrower and narrower. In a ten-second trial the gratings go from very wide to very narrow. The big ones make big signals and the small ones make smaller signals until you can no longer distinguish them from the ongoing electrical activity of the brain. A calculation was then done to fit a line to the data in order to come up with an estimate of acuity. It was a really interesting test, and apparently, Ian is right on schedule for babies his age. It was cool to see on the graphs at the end of the experiment how the visual portion of his brain reacted strongly to the wide, dark lines, but had less activity while the thin, light lines were on the screen. Below are two pictures the optometrist took during the experiment. You can click on them for a bigger view.

--Lisa