ADHD affects focus by disrupting regulation within the brain's networks.
The Default Mode Network (DMN) activates during rest or daydreaming but is normally turned off when concentrating.
The thalamus regulates and coordinates information between the brain’s network.
In ADHD, regulation from the thalamus is weakened and the DMN remains active even during tasks, leading to distractions.
Medications like Ritalin may enhance the thalamus’ ability to regulate the DMN activity
Self-monitoring strategies, such as setting timers or using audio cues, help individuals refocus attention during tasks without trying to prevent DMN intrusions.
Introduction
This was an assignment I worked on for my Master's of Education that I thought other's might benefit from (and Tumblr specifically would be interested in). The goal was to create a handout that our students could use to understand behaviour, so I targeted this at my high school biology students.
Standard disclaimer that ADHD (which I don't have but have something close to it) is a complex system within the brain. We don't fully understand it. This is just a glimpse into one of many facets of the disorder.
Brain Networks
Attention Deficit Hyperactive Disorder is a complicated condition whose biology is not fully understood. In High School, we often describe brain functions as being based in the cerebral lobes, but this is not the full truth. In reality, the brain is made up of a series of networks that are in constant communication with each other. By sending signals back and forth along various networks, the brain creates the behaviours of all humans and many animals. It is currently believed that ADHD is partially the result of miscommunications within these networks (Fassbender et al 2009; Rubia, 2018).
The Default Mode Network
One network within the brain is the Default Mode Network (DMN), which takes control when the brain doesn’t have anything to focus on, such as when the body is at rest or the mind is wandering (Fassbender et al, 2009). The DMN is largely based in the medial regions of the frontal, parietal, and temporal lobes, where the left and right hemispheres face each other (Fassbender et al 2009; Cunningham et al, 2017; Rubia, 2018). While the workings of this network aren’t fully understood, it is believed to be involved in making connections between unrelated memories. This is the basis of reflection and self-awareness, allowing the brain to see patterns across past events, as well as predict what may happen in the future (Cunningham et al, 2017; Li et al, 2021; Schwabe et al, 2022).
Image from Neuroscientifically Challenged, who also have a great article on the DMN
Attention Shifting
Normally, the DMN is only active when the brain is at rest. When the brain has something to focus on, the DMN deactivates and another neural network takes its place (Fassbender et al, 2009). If the brain needs to focus on a particular task, the Executive Control Network takes over, directing the brain to do that specific job. If an environmental stimulus catches the brain’s attention, the Salience Network takes over instead, prompting the brain to evaluate if it is interesting or dangerous (Schwabe et al, 2022). In both cases, regions of DMN become less active, which means the network isn’t as effective at doing its job. This may sound like a bad thing, but it is actually very good. It allows the brain to focus on the task at hand and makes it much less likely that random, unrelated thoughts will intrude when a person is trying to concentrate.
The DMN & ADHD
The mind wanders when the DMN is active and able to look for connections between memories and in most people, this happens when the brain is not occupied. In a classroom or work setting, this means they only start daydreaming when they aren’t engaged by what they are doing and stop paying attention to it. While this can happen to people with ADHD, it is not always true. In ADHD, the DMN does not fully deactivate when other networks in the brain take over. Instead, portions in the frontal and parietal lobes remain active (Fassbender et al, 2009; Christakou, 2013; Rubia, 2018; Salvart et al, 2018). Despite “inattentiveness” being a typical description of students with ADHD, their attention can wander even when they are fully engaged in a task because their DMN is still active. Their distractibility is not a matter of effort or attitude, but the result of contradictory signals within their brain, telling them to pay attention and let their mind wander at the same time.
The Thalamus & ADHD
While it is not always included in the DMN, there is evidence that the thalamus is strongly connected to the network (Cunningham et al, 2017; Li et al, 2021). While the thalamus is usually thought of as a relay for the senses, it is also involved in regulating and coordinating information throughout the brain. The connections allowing that regulation to take place are weakened in cases of ADHD (Qiu et al, 2010). It is possible that those weaker connections mean the signals telling the DMN to deactivate when the brain is trying to focus are not as strong, making it much more difficult.
Why Does Ritalin Help?
Methylphenidate, better known by its brand name Ritalin, is one of the best known ADHD medications. Ritalin is a stimulant, which strengthens signals within the brain, ironically causing the default mode network to be less active. Why this happens is still being studied, but it appears that Ritalin helps stimuli be more attention-grabbing, makes the DMN regulate itself better, and supports the thalamus’ ability to regulate the DMN (Demiral et al, 2018; Santos et al, 2019). Taken together, these effects can help decrease the DMN’s intrusions in a person's thought process, making them less distractible.
Supports
If you struggle with attention due to ADHD, self-monitoring is an effective strategy to help keep yourself on task. The goal with self-monitoring is not to prevent the mind from wandering, but to create awareness of when your mind starts to wander so you can refocus your attention. One common strategy is to set a timer or use another regularly occurring audio cue. When you hear the cue, record on a cue card whether you are on task or off task, then return to the work you are supposed to be doing (Rief, 2016). Pomodoro soundtracks, many of which are available on Spotify and Youtube, would also work with this strategy because they have audio cues every 25 or 50 minutes. This strategy is effective because it doesn’t try to prevent the DMN from intruding, but on refocusing you so you can achieve the goal you have set out to complete.
References
Christakou, A., Murphy, C. M., Chantiluke, K., Cubillo, A. I., Smith, A. B., Giampietro, V., Daly, E., Ecker, C., Robertson, D., Murphy, D. G., & Rubia, K. (2013). Disorder-specific functional abnormalities during sustained attention in youth with attention deficit hyperactivity disorder (ADHD) and with autism. Molecular Psychiatry, 18, 236–244. https://doi.org/10.1038/mp.2011.185
Cunningham, S. I., Tomasi, D., & Volkow, N. D. (2016). Structural and functional connectivity of the precuneus and thalamus to the default mode network. Human Brain Mapping, 38(2), 938–956. https://doi.org/10.1002/hbm.23429
Demiral, Ş. B., Tomasi, D., Wiers, C. E., Manza, P., Shokri-Kojori, E., Studentsova, Y., Wang, G.-J., & Volkow, N. D. (2018). Methylphenidate’s effects on thalamic metabolism and functional connectivity in cannabis abusers and healthy controls. Neuropsychopharmacology, 44(8), 1389–1397. https://doi.org/10.1038/s41386-018-0287-2
Fassbender, C., Zhang, H., Buzy, W. M., Cortes, C. R., Mizuiri, D., Beckett, L., & Schweitzer, J. B. (2009). A lack of default network suppression is linked to increased distractibility in ADHD. Brain Research, 1273, 114–128. https://doi.org/10.1016/j.brainres.2009.02.070
Li, J., Curley, W. H., Guerin, B., Dougherty, D. D., Dalca, A. V., Fischl, B., Horn, A., & Edlow, B. L. (2021). Mapping the subcortical connectivity of the human default mode network. NeuroImage, 245, 118758. https://doi.org/10.1016/j.neuroimage.2021.118758
Qiu, M.-guo, Ye, Z., Li, Q.-yu, Liu, G.-jiu, Xie, B., & Wang, J. (2010). Changes of brain structure and function in ADHD children. Brain Topography, 24(3-4), 243–252. https://doi.org/10.1007/s10548-010-0168-4
Rief, S. F. (2016). How to reach & teach children & teens with Add/Adhd. Jossey-Bass, a Wiley Brand.
Rubia, K. (2018). Cognitive neuroscience of attention deficit hyperactivity disorder (ADHD) and its clinical translation. Frontiers in Human Neuroscience, 12. https://doi.org/10.3389/fnhum.2018.00100
Salavert, J., Ramos-Quiroga, J. A., Moreno-Alcázar, A., Caseras, X., Palomar, G., Radua, J., Bosch, R., Salvador, R., McKenna, P. J., Casas, M., & Pomarol-Clotet, E. (2015). Functional imaging changes in the medial prefrontal cortex in adult ADHD. Journal of Attention Disorders, 22(7), 679–693. https://doi.org/10.1177/1087054715611492
Santos, P. H., Gonçalves, R., & Pedroso, S. (2019). ¿Cómo afecta el metilfenidato al circuito de activación por defecto? Revisión Sistemática. Revista De Neurología, 68(10), 417. https://doi.org/10.33588/rn.6810.2018487
Schwabe, L., Hermans, E. J., Joëls, M., & Roozendaal, B. (2022). Mechanisms of memory under stress. Neuron, 110(9), 1450–1467. https://doi.org/10.1016/j.neuron.2022.02.020
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