Written by: Rohan Kumaran
Edited by: Wonjin Ko
You’re running late, you’ve just remembered that scheduled meeting that almost slipped your mind, and you’re scrambling to look for your keys as you grab your breakfast on your way out of the door. Of course, now is the moment that your clothes seem to get stuck on the doorknob as you head out– we’ve all been there. Surprisingly, amidst this chaos, your erratic thoughts and actions actually have a subconscious, psychological origin: it’s called set-shifting. (1)
Not all tasks in the modern human’s life are made equal. Set-shifting, or task-shifting, is an integral mental process in our lives– one that is ongoing and often goes unnoticed. Some activities require minimal attention, while others demand our full effort. It’d either be excessive or dangerous to devote the same attention to an anonymous survey as you would an airborne BMX stunt. But there's an even more intriguing phenomenon at play– while we subconsciously shift between doing a task quickly or precisely, a specific part of our brain consciously guides us through switching between tasks, all in the hope of gaining some reward. This is what psychologists refer to as “goal-directed behavior,” and it’s one of the executive functions that the prefrontal cortex directs. (2) While our working memory juggles our immediate, short-term concerns, executive control oversees those cognitive processes and pairs working memory with impulse inhibition– avoiding distractions– to complete tasks. This fascinating interplay of orienting, attending task completion, and minimizing distraction enables us to confront our daily challenges and navigate the complexities of modern life.
Our human experiences make it rather intuitive that set-switching is a comprehensive term which acknowledges the nuances of each duty. Some tasks are completed by repetition until an ‘undone’ pile is sorted through– like responding to each email in your inbox one by one or folding each item of laundry in the pile that just came out of the dryer. Your goal-directed behavior is the same– you are in the same external environment, with a more-or-less identical internal state, completing very similar versions of the same task (i.e. replying to emails, folding laundry).
Some tasks require divided attention, like babysitting a child. You’re considering if they’re fed, going to bed, if unused appliances are switched off, or if you remembered to run all of the expected errands. The last type of task-switching is one I find particularly thought-provoking– approaching the same task with varying objectives. This kind of flexibility requires a change in our mental set– essentially, how we prime ourselves to approach a problem. It could mean choosing between being quick and efficient or meticulous and accurate. When in a task-switching situation that involves completing the exact same task in different manners (i.e. fast vs accurate), you exhibit flexibility on the basis of quickness and caution.
Testing your task-switch
The Shenhav Lab at Brown’s Cognitive, Linguistic and Psychological Sciences (CLPS) department aims to understand and measure attention and motivation, as measured by how research study participants respond to rewards during task-based objectives (3). Their work focuses on learning efficacy, cognitive control, attention allocation, and how control adjustment costs limit goal flexibility. In other words, they collect real-time data on participants’ brain waves, reaction speeds, and performance while completing a simulated game– the Stroop task– that requires them to task-switch. The Stroop task faces participants with textual words of familiar colors– red, blue, green, and yellow– which are printed in either the same or a different color. This dissonance between word semantics and the visual stimulus of the color text assesses participants’ ability to inhibit cognitive interference when faced with incongruent stimuli. (4, 5)
Attention, focus, and overall performance are affected by the nature of a certain task. However, what makes these experiments interesting is when researchers introduce discrepancies intended to uncover fluctuations in completing the game. Clinical psychology and cognitive neuroscience studies examining these fluctuations in performance are concerned with control adjustment costs– the tradeoff in performance when tasked with responding either quickly or accurately (6).
Participants who are familiar with psychological studies, CLPS concentrators, or have previously had an EEG might be more comfortable with the task and accordingly, might be likely to perform better. (7) While those incidental factors are largely out of the lab’s control, there are some other confounders that researchers and assistants in the lab are vigilant about minimizing. The main interest of the game is to study task-switching– the effects of executive control. Throughout the hour of the study, however, it is likely that some participants have trouble remembering rules, feel fatigued or demotivated, or even just get hungry– properties we can’t necessarily estimate or control for but might reduce participants’ alertness. (8) Researchers effectively mitigate the effects of these behavioral factors on data simply by engaging participants and being talkative. Conversing with subjects about school, hobbies, and ensuring the conversation revolves around them is a great way to make participants comfortable and motivated to attend to the task. (9) Building a good rapport and ingratiating yourself to subjects before an EEG session has a shocking effect on the quality of data!
So, now, the participant is ready to read colored words, tap keys, and wear a cap that costs up to $1,000 yet is hardly fashion-forward. It's time for the moment everyone has been waiting for – to open up the real-time EEG reading. The researchers demonstrate to participants how they can observe a shift in their sharp beta waves while they are alert, changing to smooth, rounded alpha waves after they take a few deep breaths and a moment to relax. Next, they ask the participants to rapidly blink, alternately glance left and right, and make facial grimaces to understand how small movements can interfere with the data. This helps the participants gain perspective on how reactive the data truly is and how vigilant they should be to limit interference. In fact, after the game finishes, researchers collect data from a second task where participants intentionally blink and glance up, down, left, and right. This data collection helps overwrite the artifacts those movements impose on the data.
Control Room to Clinic
Okay, so it makes sense that there are some changes in reaction time and accuracy when participants attempt to be quick or cautious, but how are the results generalizable if no one is just sitting around doing the Stroop task?
While EEG indications likely won’t be used to prescribe specific treatment plans or medications, its strength lies in getting high-resolution data quickly. Typically, high-performance liquid chromatography (HPLC) and microdialysis are the lab techniques of choice to measure neurotransmitter concentrations, but EEG is rapidly being studied as a real-time alternative. (10,11)
EEG’s pioneering attribute is its ability to identify changes and deficits in various neurotransmitters like acetylcholine (regulator of the rest-and-digest nervous system and the connection between the nervous and muscular systems) and monoamines like dopamine, serotonin, and noradrenaline, which regulate our alertness, mood, sleep, and motivation. Discerning levels of acetylcholine and the monoamines, EEG is a powerful resource for identifying sleep disorders, personality disorders, and neurological disorders.
Sleep disorders have a strong tie to neurotransmitter levels– there’s a characteristic decrease in acetylcholine (that’s the one active in your neuromuscular junctions–– checks out, right?) and a relatively sustained level of monoamines noradrenaline and serotonin (those regulate your mood and sleep). (11) Given what we know about chemical messengers in the brain and how EEG can track them, EEG is becoming a favored tool in identifying and understanding parasomnias and narcolepsies. (12)
Clinical psychiatry is another emerging application of EEG as some researchers begin supporting how it could index neurotransmitter levels across mental disorders, like OCD or ADHD. (11) Opportunities for mental and personality disorders are expansive for EEG because of its simultaneous ability to discern attention, focus, memory, and neurotransmitter activity. In fact, EEG is making waves (pun intended) in the study of behavioral disorders, like anxiety and depression. Studying these psychiatric conditions with EEG expanded our understanding of neurological disorders like epilepsy. (13)
EEG has pushed our anatomical understanding of epilepsy to new heights. Its ability to identify where speech, memory, and movement functions originate has proven monumental in understanding where seizure disorders arise. In terms of saving healthcare dollars, reducing lab work, and operations, EEG is a superstar for treating epilepsy. Epilepsies can be either generalized or focal (or multifocal), meaning they originate from either the whole brain or certain regions. EEG, especially when coupled with fMRI (which the Shenhav Lab and other cognitive neuroscience labs at Brown study, too!), can be as precise as identifying particular focal points causing seizures. (14,15) Perhaps the best part of this revolutionary capability is that it can evaluate disorders and tentatively replace an operation procedure which requires specialized electrodes to be inserted directly into brain tissue. (16)
The popularization of EEG is an important development in clinical psychology and neuroscience because of its broad applications and strength in providing high-resolution, real-time data. With a relatively easy setup and accurate data capture, EEG is an instrumental tool in detecting and classifying neurological disorders– like Alzheimer's, ALS, and dementia– with one common characteristic. Treatment expenses for neurological disorders are extremely sensitive to early diagnosis. The European Brain Council published the results of a case study detailing how timely intervention could “improve survival rate, reduce complications and disability…and lower treatment costs.” (17) Progressive neurodegenerative diseases with worsening symptoms often include a very long, expensive prognosis, burdening patients and family for years. It is closer to a rule than an exception that they “deplete financial resources, placing a substantial burden on state Medicaid programs.” (18)
For that reason, early, accurate, and cheap identification of these conditions is vital for afflicted patients’ health and financial well-being. EEG serves as a primary biomarker in the early detection of dementia and Alzheimer’s. (19,20) In fact, “resting-state EEG can reliably and quantitatively capture abnormal patterns of motor and cognitive network disruption in ALS.” (21) EEG has even exceeded some clinicians’ expectations for simply detecting the disease, as it is now being used to [distinguish] behavioral subphenotypes– “ALS can no longer be considered a single disease with a singular pathophysiology and clinical course” reads a publication from the article Brain. (21)
Recording precise fluctuations from electrical impulses from your neurons at millisecond precision by simply wearing a spandex and tin cap seems futuristic, but the development is evolving the fields of neuropsychology and medicine. As we collect data and reach conclusions on attentiveness and performance, we gain a better understanding of our cognition in daily life. As EEG’s non-invasive, real-time, high-resolution data collection becomes more refined, it becomes a more powerful diagnostic tool in clinical psychiatry. With high precision and a relatively affordable price tag, electroencephalography can help evaluate psychiatric patients without operation, save many healthcare dollars, and uncover how we think and approach challenges, one wave at a time.
4. What the Stroop Effect Reveals About Our Minds [Internet]. [cited 2023 Nov 6]. Available from: https://lesley.edu/article/what-the-stroop-effect-reveals-about-our-minds#:~:text=According%20to%20an%20article%20in,of%20a%20second%20stimulus%20attribute.%E2%80%9D
10. Cifuentes Castro VH, López Valenzuela CL, Salazar Sánchez JC, Peña KP, López Pérez SJ, Ibarra JO, et al. An Update of the Classical and Novel Methods Used for Measuring Fast Neurotransmitters During Normal and Brain Altered Function. Curr Neuropharmacol. 2014 Dec;12(6):490–508.
13. Sand T, Bjørk MH, Vaaler AE. Is EEG a useful test in adult psychiatry? Tidsskr Den Nor Legeforening [Internet]. 2013 Jun 11 [cited 2023 Nov 7]; Available from: https://tidsskriftet.no/en/2013/06/eeg-useful-test-adult-psychiatry
14. Laufs H, Thornton R. 4.2 Clinical Applications: Epilepsy. In: Ullsperger M, Debener S, editors. Simultaneous EEG and fMRI: Recording, Analysis, and Application [Internet]. Oxford University Press; 2010 [cited 2023 Nov 7]. p. 0. Available from: https://doi.org/10.1093/acprof:oso/9780195372731.003.0018
16. Department of Neurology [Internet]. [cited 2023 Nov 7]. Evaluation for Epilepsy Surgery. Available from: https://www.med.unc.edu/neurology/divisions/epilepsy-1/epilepsy-surgery/evaluation-for-epilepsy-surgery/
20. Houmani N, Vialatte F, Gallego-Jutglà E, Dreyfus G, Nguyen-Michel VH, Mariani J, et al. Diagnosis of Alzheimer’s disease with Electroencephalography in a differential framework. PLoS ONE. 2018 Mar 20;13(3):e0193607.