That Neuroscience Guy - Neuroscience Bites-Anosognosia

Episode Date: February 8, 2023

Last week, we discussed the neuroscience behind spatial neglect. This week, we discuss an extreme case of neglect called Anasagnosia, where patients can't process anything on the left side of their visual field. 

Hi, my name is Olof Kregolsen and I'm a neuroscientist at the University of Victoria. And in my spare time, I'm that neuroscience guy. Welcome to another Neuroscience Byte. On the Byte last week, we talked about neglect and what neglect was. Well, there's an even more extreme form of neglect. Now, just briefly, if you remember, neglect is an attentional disorder, typically due to damage to the right parietal cortex, where you basically don't pay attention to left visual space. Well, anosognosia is an extreme form of neglect. And people with anosognosia don't know that the left side of the world exists.

True story. What's crazy about it is the way you can test this with people that have anosognosia. For instance, if you have someone with anosognosia and you put a tray out in front of them and you ask them to hold the tray by putting their hands underneath, the tray will fall because what will happen is they'll put their right-hand side under the right-hand side of of the tray but they'll neglect or forget to put their left hand side under the left hand side of the tray so the tray will imbalance and tip over. In more extreme cases you can actually take the person's left arm and pull it into right visual space so they can see the arm but because it's coming from left visual space, they'll actually tell you it's someone else's arm. They won't believe it's their own. Now,

if you force them to follow the arm and stare in and put the arm into central vision, then they will eventually come to that conclusion. But unless they do that, they believe the arm belongs to someone else. And here's an even weirder test you can do. You can hold a mirror so it looks like there's something over their right shoulder, say a tennis ball, and you can ask them, well, can you reach for the tennis ball? And they'll look in the mirror and they'll know it's over their right shoulder. So what they'll do is they'll reach back over their right shoulder and get the tennis ball, just like you or I would. But if you

reposition the mirror so it looks like that the tennis ball is over their left shoulder, all right, they will reach into the mirror. So they'll reach out with their right hand into the mirror to try to grab the tennis ball because they literally do not know that the left side of the world exists. Now, this again is an attentional disorder. And we talked about attention back in season one, and we actually talked about neglect and anosognosia very briefly, but this is just a little reminder and review. So these are both attentional disorders, neglect and anosognosia. In neglect, it's an indifference to leftal disorders, neglected anosognosia. In neglect, it's an indifference to left visual space. In anosognosia, it's a complete disbelief that

left visual space or the left side of the world even exists. I'll put up a cool YouTube video on the blog. Remember, my blog is on thatneuroscienceguy.com. Click on blog. We try to support the bites with the blog. So we put up some images and stuff. So there's some stuff there. And of course, there's links to our Etsy store, Patreon. Remember, Twitter, at thatneuroscienceguy. Send us ideas. We're already thinking season five.

And of course, thank you so much for listening. And thank you for subscribing to the podcast. My name is Olaf Kregolsenson and that's another neuroscience bite i'll see you on the weekend for another full episode