The image of mental fatigue

Functional magnetic resonance imaging offers insights into mental fatigue

We all perhaps know the feeling of mental exhaustion, but what does it mean physiologically to have mental fatigue? A new study carried out using brain scans could help scientists uncover the neurobiological mechanisms underlying mental fatigue.

According to Bui Ha Duc and Xiaoping Li of the National University of Singapore writing in a forthcoming issue of the International Journal Computer Applications in Technology, mental fatigue has become commonplace as many people face increasing mental demands from stressful jobs, longer working hours with less time to relax and increasingly suffer sleep problems. Mental fatigue has received attention from those involved generally in health and well being as well as from the military and transport industry. After all, mental fatigue not only affects the health of individuals but can also have implications for road safety and international security.

The researchers used functional magnetic resonance imaging (fMRI) to monitor activity in the brains of ten student volunteers (male and female aged 19 to 25 years) deprived of sleep for 25 hours and given a simple task repeatedly through that period. They carried out scans at 9am, 2pm, 3am, 9am the following day. All volunteers had to have avoided alcohol and caffeine for the 24 hours prior to the experiment, were all physically and mentally fit prior to participation and none had any sleep problems.

The activation of the left thalamus increases with sleep deprivation, going in an exactly opposite trend to the inferior parietal that (following the circadian rhythm) decreases in activation from 9 am to 3 am next day and then increases in activation. This finding fits with logic as the inferior parietal cortex integrates information from different sensory modalities. As all the information has to go through the thalamus and then is sent by the thalamus to the inferior parietal, when the inferior parietal decreases in activation, the thalamus must increase its activation to get the information sent through.

The team explains that a gradual increase in mental fatigue led to decreased activity in the volunteers’ brains in specific regions: the anterior cingulate gyrus, right inferior frontal, left middle frontal and right superior temporal cortex. The anterior cingulate cortex has been described as an interface between motivation, cognition and action, and has been implicated in using reinforcement information to control behavior. The fMRI scans suggest that decreased activity in this part of the brain is therefore linked to those familiar feelings of mental fatigue including lethargy and slowness of thinking.

“The research provides a neurophysiologic basis for measuring the level of mental fatigue by EEG, as well as for the intervention by non-invasive neural stimulation to maintain wakefulness,” the team says. “We have developed devices for both, which will be commercialized by our spinoff company, Newrocare Pte Ltd.”

Oh, man.

I have just been exhausted lately. Exhausted for no good reason, either. I mean, it’s okay to be exhausted from working a 12-hour work shift or something like that, but I’m not. I just wake up tired, go to work tired, come home tired, and go to bed slightly less tired (isn’t it stupid how that works?).

Now, there’s a very good chance I’m just tired because I’m so out of shape these days. I went to the doctor yesterday, and while I happily didn’t gain any (more) weight since I’d seen him four months ago, I didn’t lose any, either, and my cholesterol and blood pressure were higher than they’d been in a while. In order to prevent myself having to go on medication four months from now, I need to lose weight. So, I’ve taken a much more serious approach to counting my calories and not eating junk food, rather than just coasting along aimlessly. I’m hoping to lose 25 pounds within four months (when I see my doctor again), and 40 pounds within seven months (the wedding!). I know I can do it. I’ve done it before. It’s only a lack of motivation that’s been stopping me, and since I really don’t want to be on heart and blood pressure meds for the rest of my life, I’ve really felt that motivation come back again.

I’ve been formulating another theory, though, to at least partially explain why I’m always so tired. Even though I have a sedentary desk job, and I know I don’t get enough regular exercise, I never let my brain rest. I’m an introvert by nature, and introverts re-energize from within. We recharge our batteries by spending time alone. Down-time is important to us. When I go too long without just letting myself relax and letting my brain cool off, I start to get tired and sometimes a little cranky. When I have to go to a social event when I’m already feeling tapped-out, I get crotchety, like an old man waiting for soup. My body isn’t really tired, but my brain is just unable to expend any more energy, and it crashes.

Sometimes, even browsing the internet isn’t really downtime, because my brain is still very active. A peaceful photo walk works, though—it’s almost like a form of meditation. There are no outside distractions, there are no instant messages, there’s just me, a camera, and peace. That’s probably why I took to photography so quickly, but also why I’m not very good at people photography. 

I’ve found that I can improve my mood and energy level a lot by just laying down in absolute peace and quiet for about 30 minutes. No distractions, just solitude. I try not to think about anything in particular, letting my mind unwind. After a while, I feel refreshed—sometimes more refreshed than after a night’s sleep.

I think I’ve been ignoring my need for downtime for too long. I need to let my brain stop and gather itself sometimes. As a society, I don’t think we pay enough attention to our levels of mental fatigue. We base everything about being “tired” on physical fatigue. I think both types of fatigue are on equal sides of the same coin, and that we can tire ourselves out mentally just as we can tire ourselves out physically. The symptoms of each can be strikingly similar!