Have you ever been surprised and then — Where was I going with this?
Interruptions to our trains of thought happen all the time, often managing to wipe our mind blank so we forget how we were going to finish that sentence.
And a new study published Monday in Nature Communications nails down exactly what in the brain may be happening when that interruption happens.
To figure it out, researchers at the University of Iowa looked at the electrical activity in the brains of 20 healthy participants and seven people with Parkinson’s disease, a neurodegenerative disorder characterised by difficulties with motor skills like walking or talking, while they subjected them to a series of sounds.
Importantly, all the participants with Parkinson’s had previously undergone some form of neurosurgery before entering the trial. This allowed the researchers to gather some critical data from deep inside the brain tissue which they normally wouldn’t be able to see. For the healthy people, they looked at brain activity using an EEG, a tool that uses sensors to monitor electric waves in the brain that goes on over the head, and for those with Parkinson’s, they were able to use an LFP, which monitors electric waves from inside the brain.
While they monitored their brain activity, the researchers showed all of the participants a series of letters. As they viewed the letters, they were interrupted by either a tone (which they’d been accustomed to hearing) or a birdsong (which they were not accustomed to hearing). Next, they were shown a second set of letters, which they had to decide either matched the first set or did not.
Compared to the people who heard the familiar tone, those who heard the surprising sound — the birdsong — were wrong more frequently, suggesting that their memory had been interrupted.
When researchers looked at the brain activity of the healthy people and the people with Parkinson’s when they’d been interrupted by surprising sounds, they found amped up activity around a part of the brain that scientists think plays a key role in coordination called the basal ganglia.
Importantly, they were able to look even closer at the brain activity of the participants with Parkinson’s who’d been interrupted by the surprising sounds. By focusing on a specific part of the basal ganglia called the subthalamic nucleus, or STN, which is normally responsible for translating signals from other parts of the brain to help with movement and coordination, they found that that area in particular was disrupted when the participant was surprised by a sound.
By learning more about what activates this area, the researchers hope to better understand why motor activity is sometimes suppressed in people with Parkinson’s.
So the next time you’re interrupted by a text and completely forget what you were going to say next, you can blame your basal ganglia for responding so extremely.