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Walk in the middle of the pavement! how (not) to travel in a straight line with CVI

One thing you will inevitably discover if you’re ever unlucky enough to have an NTBI, is exactly how much your brain has always done for you in the background, without you ever being aware of it. For me this came as a rather unpleasant surprise, as it does to many. It is only when you lose the ability to process it, that you become aware of the sheer volume of data that your brain continuously has to deal with, and the short period of time in which it must be processed to keep your image of the world around you up-to-date.

Een brede stoep met vierkante tegels.

Tervuren, April 2020


Walking in a straight line in the middle of the pavement: it can’t be that difficult. Or so we think. You take a step: first you put your left foot forward, then your right foot. And you make sure you stay in the middle. What could be easier? But the reality is a bit more complicated. I can walk well – extremely well – I can walk for miles without using the wrong foot once! But that bit about the straight line, how do you do that? That’s not so straightforward, if you’ll excuse the pun.

Finding the middle?

Where exactly is the middle of the pavement? You need a lot of information to work that out properly. Where is the left-hand side of the pavement? Where is the right-hand side? How far are they away from each other? Where is the midpoint between the two? How far and in what direction am I from that midpoint? How do I need to move to get there?

A healthy brain can work all that out in an instant, without you ever being aware those calculations are being made. Before you can even begin to start moving along the street, you need to be able to hold all these things in your head at the same time. And as you start to walk, all those distances, angles and calculations are constantly changing. But what happens if your brain can’t keep up?

If you ask me to stand in the middle of the pavement, I first look to the left and locate the left edge of the pavement. Then I look to the right to locate that. But now, since I cannot keep those two pieces of information in my head at the same time, I am no longer sure of the location of the left-hand side of the pavement. And so I look left a second time to relocate it. But now I have forgotten where the right side is! So obviously, I need to look right. And I find myself in a kind of feedback loop. One that can sometimes continue for a long time!

People who know me well will undoubtedly recognize the head-shaking which happens to me so often.

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Published inAt home in TervurenCVI - Cerebral Visual ImpairmentNTBI - Non-traumatic brain injuryWritings from rehab

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