Decreased Alertness Influences Brain Activity During Decision-Making
Post by Lincoln Tracy
The takeaway
The decisions we make every day are informed by our surrounding environment and internal processes. Being drowsy means we are slower to react to external information, and we react incorrectly more often than when we are alert due to differences in how our brains process the information.
What's the science?
Humans make countless decisions each day that are informed by external information, prior knowledge, and evidence. However, we have a limited understanding of how changes in alertness impact neural and cognitive processes. This week in The Journal of Neuroscience, Jagannathan Bareham and Bekinschtein used electroencephalography (EEG), behavioral modeling, and an auditory tone localization task to explore how low alertness modulates evidence accumulation-related processes.
How did they do it?
The authors recruited 32 healthy participants (14 males, mean age of 24.5 years), who completed an auditory tone localization task. The task involved listening to a series of guitar chords and indicating whether the sound came from the left or right of their midline. Participants were tested under alert and drowsy conditions. The alert condition was shorter (8 minutes long) and involved participants sitting upright with the lights on and being given specific instructions to stay awake. In contrast, the drowsy session lasted between 1.5 and 2 hours with participants reclined in the dark, given a pillow, and allowed to fall asleep. The number of incorrect responses and reaction times was recorded. Participants wore an EEG cap to record electrical activity in different areas of the brain during the auditory tone localization task.
What did they find?
First, the authors found participants made more localization errors on tones being played on their left-hand side during the drowsy condition compared to the alert condition, confirming the original study from Bareham and colleagues from 2014. Second, they found participants were slower to react during the drowsy condition, meaning the brain required a longer time to process the direction of the auditory tone. Third, they found that the brain activity necessary to decide whether the sounds came from the left or right side was not only less efficient when drowsy, but came later, suggesting a delayed mental process when alertness is decreased. Finally, they found the processing of the auditory began in the frontocentral brain regions before shifting to more central and rear parts of the brain more quickly during the alert condition compared to the drowsy condition, concluding that the brain operated in a different spatial configuration in drowsiness, and at a much later time.
What's the impact?
This study provides new data on how the brain tries to combat decreases in alertness by recruiting additional brain regions to help process external information. These findings shed light on how brain activity tries to adapt to solve problems based on our internal state.
