How does your brain decide what to pay attention to? This might seem like a simple question, but think about all the things going on around you that it has to filter out. You probably aren’t noticing every shadow on the wall behind your computer screen, even though it’s in your field of vision – or at least you didn’t until I mentioned it!
Sometimes the answer is fairly obvious: we consciously choose what to focus our attention on. For instance, right now you are choosing to focus on reading the words on this blog (thank you, by the way!). But there are also times when our attention is not determined by our conscious choices. Experiments have shown that if we learned in the past that something was important–say, because it was associated with a reward of some kind – our brains will automatically direct more of our attention in that direction whenever that thing pops up. Dopamine, one of the brain’s neurochemicals, is thought to help our brains with this; it acts as a kind of filter for all the information we process.
This could be really important for people with Parkinson’s disease because Parkinson’s disease causes a reduction in brain dopamine levels. So does that mean that people with Parkinson’s disease have a less effective attention filter? To address this question, we designed a research study to determine if Parkinson’s disease changes people’s ability to selectively allocate their attention: i.e., to pay more attention to more important things, and to pay relatively less attention to less important things?
In order to answer this question we had people with and without Parkinson’s disease play a game on the computer. In the first part of the game, participants had to find either a red or a green circle among several other coloured circles on the screen, and say in which direction a line inside of it was pointing as quickly as possible. If they got it right, they got real money. There was also a little trick: trials that had a green circle gave more money than trials with a red circle. They did this over 200 times–the idea was to train their brains that green circles were associated with a bigger reward (and so were more important) than red ones.
Once they were done, they played the second part, which was very similar except that now they had to spot the odd shape out–a square–among a bunch of circles. Color didn’t matter anymore. But there was a twist: we created some distraction by making one of those circles (which now participants were supposed to ignore!) red or green, just like in the first part. The theory was that people would have a harder time spotting the square if a green circle was also on-screen than if a red circle was on-screen , because green, which had been associated with more money, would be more distracting. In other words, their attention would be automatically drawn to the green circle.
This might all seem a bit abstract, so let’s think about a real-world example. If you were walking down the street and there was money on the ground, which would distract you more: a $1 bill or a $100 bill? Probably the $100 bill, but that’s not because the $100 bill is much brighter or easier to see; it’s because $100 is a lot bigger of a reward than $1! The green circles were like a $100 bill: the experiment was designed so that participant’s brains would learn that the green circles were “more important” to pay attention to than the red ones because they signified more reward.
So what did our study show? As we expected, people without Parkinson’s disease seemed to be more distracted by the more rewarding green circles than the red ones. However, people with Parkinson’s disease were equally distracted by the red and the green circles. They did not seem to allocate more or less attention based on reward!
This raises a lot of questions: If people with Parkinson’s can’t rely on reward to help guide what they pay attention to, do they use other mechanisms? Or, if their brains have more difficulty tuning out “less important” information, could this make it harder for them to focus on the things they should focus on? Also, we had expected that the dopamine medications people with Parkinson’s disease take might help them focus their attention on rewarding stimuli, but it didn’t seem to. We are now looking into other brain neurochemicals that can be affected by Parkinson’s disease to better understand how Parkinson’s might affect the “attention-allocation” process.
Written by: Alex Silver
Alex Silver is a former full-time medical writer who is beginning his residence in Neurology at Dalhousie University this year. He is passionate about science communication, learning about the human brain, and any and all dogs.
You can read about this in more detail in the full study which is linked here: https://doi.org/10.1038/s41598-021-97526-7
And if you’re interested in participating in our ONLINE research studies, or have comments to share with us, please don’t hesitate to contact us at: madeleine.sharp@mcgill.ca or sharplab.neuro@mcgill.ca.
We need all the help we can get to advance on our understanding of how Parkinson’s disease affects people!
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