CogBlog – A Cognitive Psychology Blog

1 in every 9 older adults (65 years and older) is currently living with Alzheimer’s disease, a type of dementia that affects memory, thinking, and behavior. But the numbers do not tell the whole story. The losses faced by these patients cannot be boxed into statistical data. Patients start to forget their memories, their loved ones… who they are! As explained by Gerda Saunders, a writer with dementia,  she began to feel like a stranger to herself. There are many forms of dementia, but Alzheimer’s disease is the leading cause, and still, there are no available treatments that stop or slow the progression of the disease: the medications just treat the symptoms. But these treatments are based on early diagnosis of the disease, and the visible signs of Alzheimer’s usually appear years after the disease started developing. So early diagnosis can be really hard. Alzheimer’s disease can stay hidden for years! When we perceive the changes, it is usually too late. But that is not necessarily a cause for despair. Simple cognitive tests can be the key to an early and accessible diagnosis!

When talking about Alzheimer’s, we usually think about the failure of episodic memory (the memory for events we experience). When someone forgets where they put their keys, or what they had for breakfast, for example. But it seems that the key to an early diagnosis of the disease is not a memory test, but tests that reveal other cognitive processes. Difficulty in focusing your attention on something, for example, can be a powerful predictor of Alzheimer’s. Attention is a mental capacity: it defines the resources we have available to perform certain tasks. For example, if you are reading a book, you don’t have the resources to write a letter about a different topic at the same time, right? Attention is also defined as a filter, determining what will be processed. If you are paying attention to a movie on the TV, you might not even notice the conversation your roommates are having on the other side of the couch. One study by Tse et al. focused specifically on tasks that required directing attention; that is, choosing voluntarily what you are going to pay attention to. The first task is called the “Stroop task”. Imagine I give you two words: green and red. The color of the font for both words is green, as in the picture below.

Then I ask you to tell me the color of the font (not what is written). Do you think you would be able to answer green for both the “green” and “red” words at the same speed? You can use a demo to see for yourself, but multiple studies say that you wouldn’t. When the color written is the same as the color of the font, we tend to name the color faster. However, if there is a mismatch in the color written and the color of the font (e.g. RED written in green) we are slower to name the color. The trick here is that reading is a common process in our daily lives. We are constantly reading something, right? In the Stroop task, though, we are asked to NOT read. And this seems to be a little more complicated for us; we must really pay attention. The same thing happens in the “Simon task”. For this task, participants see arrows on a screen (such as in the image below). They are asked to ignore the location of the arrow (right or left side of the screen) and just say where the arrow is pointing to.

In the picture above, you would say right for the red arrow (even though it is on the left side) and left for the blue arrow. AAAAH! Super confusing, I know! Once again, there are two pieces of information that don’t match – the location vs. where the arrow is pointing – so we need to pay attention to accurately complete the task. The last task used by Tse et al. was the “Switching task.” The participants were always presented with a letter and a number. But there were two possible tasks to perform: say if the number was odd or even, or if the letter was a consonant or a vowel. It seems straightforward, right? The trick was that the participants needed to keep track of the task they should be performing at each time. The first two tasks were about the letter, the next two about the number, and so on. If it seems hard to understand the task, imagine performing it! The figure below can help you to understand the task, by showing an example of the correct answer for 5 trials.

You can also perform a demo (with a few distortions in the way it is performed, but following the same reasoning!). If you performed the demo, you noticed that it requires A LOT of attention to perform a task while recalling what task you should be doing. As you can see, all the tasks analyzed by Tse et al. rely on paying attention to what you are doing. The study showed that participants in the early stages of Alzheimer’s disease were slower than healthy older adults in performing the tasks. This suggests that the ability to direct attention is prejudiced in Alzheimer’s.

But more than being impaired in Alzheimer’s patients, attention can also work as a predictor of the disease. In a study by Spieler et al. that happened from 1992 to 1994, 12 of the participants initially classified as healthy older adults later developed Alzheimer’s disease. Some of the researchers involved in the study, together with other colleagues, decided to investigate if older adults who developed Alzheimer’s after the conclusion of the study had also performed worse when doing the cognitive tasks from 1992 to 1994 (Balota et al.). The study showed that, when performing the Stroop task, the 12 individuals made more errors (saying the color written rather than the color of the font) and responded slower than healthy older adults, showing that attention is a strong predictor of Alzheimer’s. One interesting thing about the relevance of attention to Alzheimer’s disease is the increasing evidence of a connection between attention and memory. A lot of scientists trying to explain how memory works suggest that we just remember what we pay attention to. We could go back to the key example: if you leave your keys somewhere without paying attention, it is very likely that you will not remember where you put them. If you were to draw a scheme, you could place attention as the entry point from the world to our memory. Because of that, it is possible that the reduced ability to pay attention contributes to memory loss in Alzheimer’s patients.

However, attention is not the only cognitive process that might be used to early diagnose Alzheimer’s disease. In 1997, Yang was conducting a study about iconic memory (the storage of our vision – that image that you keep seeing in your mind for a short time after the real image is gone), and he was surprised to notice that one of the participants had an unusually short iconic memory duration. Iconic memory normally has a very short duration (less than a second), but the participant in Yang’s study showed an even faster decay. From this study, Lu, Neuse, and Dosher decided to see if iconic memory duration could be a predictor of Alzheimer’s disease development. The researchers used a task called the “partial report technique” to analyze the duration of the participant’s iconic memory. In the task, the participants see three rows of letters (as shown in the figure below), and right after the image disappears, they are asked to recall only one of the rows. Participants usually remember around 3 items of that row. As the row is asked after the image disappears, it suggests that the whole image (with all its rows) was available in the participants’ memory, but it was “deleted” really fast (so they just had time to report the 3 items).

The participants of this study were diagnosed previously with Mild Cognitive Impairment (MCI). It is normal to start forgetting things and getting slower in certain tasks when we get older. But not everybody is going to have the profound decline that characterizes dementia. Because of that, scientists and doctors try to differentiate the cognitive decline expected with age from the more marked decline related to dementia. MCI is the stage in between these two – the person is, for example, forgetting more than a healthy older adult, but still not showing the signs that characterize dementia. Here it is important to make a distinction. Most studies start by applying the tests to participants with MCI, but not all MCI patients will develop Alzheimer’s disease. The goal of these studies is to predict what participants will later develop the disease. To be able to make a prediction, the participants cannot already be diagnosed with Alzheimer’s disease, right? So, the MCI is the perfect stage to study the predictive nature of cognitive tasks. This prediction is then confirmed or refuted after years of the researchers following the participants. In this study, patients with MCI who later developed Alzheimer’s showed significantly shorter iconic memory. The researchers suggested that, for the task, the participants need to identify the letter, but also keep track of where on the screen the letter was. In the way our brain works, it is not enough, for the example in the figure above, to say that there was a letter J in the first row. You need to remember that the J was in the second position, next to the W and the D. These are two different pieces of information, and it turns out the hippocampus (a structure in our brain) is very good at combining pieces of information. But guess what? This structure is affected in the early stages of Alzheimer’s! Because of that, this kind of cognitive task can work as a diagnosis for the early brain damage caused by Alzheimer’s disease.

The most wonderful thing, however, is that these cognitive tasks are effective in diagnosing the disease early and they have also shown to be as effective as biomarkers (the biological measures of a certain disease, such as collecting blood to diagnose high levels of cholesterol). Currently, the most successful way to diagnose Alzheimer’s disease early is by collecting certain fluids found in our brain and spinal cord. The main issues are that these exams 1) are not easily available for a large portion of the population for being expensive, and 2) are usually uncomfortable for the patient (it is necessary to collect them directly from the spine, a very invasive procedure!). A study by Palmqvist et al compared simple cognitive tests to biomarkers. The study analyzed the efficacy of the diagnosis using two cognitive tests. The mini-mental state examination is a series of tests analyzing attention, memory, orientation, language, and visual-spatial skills. Participants also performed the clock drawing test. To properly draw a clock, you need visual-spatial, numerical, and planning skills, so the clock drawing task can analyze all these skills. The study suggested that the cognitive tests are as effective as the biomarkers (and we all can agree that they are much more accessible too)! The researchers also showed that combining both kinds of tests can provide even more accurate diagnoses. This study can be an important turning point in how Alzheimer’s disease diagnosis is performed.

Alzheimer’s disease is a cruel and prevalent disease. It disconnects people from their loved ones, their memories, and their identities. As Alzheimer’s is a degenerative disease, the symptoms only get worse with time. Because of that, an early diagnosis might be one of the only possibilities to end the disease. Cognitive tasks are shown to be beneficial in diagnosing the disease, not only because of their efficacy in detecting early (and usually unnoticed) signs but also because of their accessibility to the population. But doctors and scientists are not the only ones involved in the fight to end Alzheimer’s! There is a lot you can do to live healthy aging and prevent the disease! And now that you know a bit more about Alzheimer’s disease, you can also do your part by raising awareness or donating! The Alzheimer’s Association raises funds for research, advocacy, support, and care. You can donate at: http://act.alz.org/goto/ColbySquad2022

Literature cited

Balota, D. A., Tse, C. S., Hutchison, K. A., Spieler, D. H., Duchek, J. M., & Morris, J. C. (2010). Predicting conversion to dementia of the Alzheimer’s type in a healthy control sample: The power of errors in stroop color naming. Psychology and aging, 25(1), 208.

Lu, Z. L., Neuse, J., Madigan, S., & Dosher, B. A. (2005). Fast decay of iconic memory in observers with mild cognitive impairments. Proceedings of the National Academy of Sciences, 102(5), 1797-1802.

Palmqvist, S., Hertze, J., Minthon, L., Wattmo, C., Zetterberg, H., Blennow, K., … & Hansson, O. (2012). Comparison of brief cognitive tests and CSF biomarkers in predicting Alzheimer’s disease in mild cognitive impairment: six-year follow-up study. PLOS one, 7(6), e38639.

Tse, C. S., Balota, D. A., Yap, M. J., Duchek, J. M., & McCabe, D. P. (2010). Effects of healthy aging and early stage dementia of the Alzheimer’s type on components of response time distributions in three attention tasks. Neuropsychology, 24(3), 300.