False Memory in Alzheimer’s Disease
By: Alina Mukherjee
Alzheimer's Disease (AD) is a brain disorder that generally appears later on in a person’s life. More than six million Americans, most of them age 65 or older, have AD (National Institute on Aging, 2023). The disease manifests itself in a slow loss of memories and cognitive processing abilities over time. Eventually, AD patients become so absent-minded (forgetful and inattentive) that it is difficult for the person to carry out even the simplest of tasks. Patients with AD not only experience “impairments in learning and memory” but also often have false memories, defined as “a clinically relevant memory distortion where a patient remembers an incorrect memory that they believe to be true” (Dewitt and Schacter, 2018). The reason they form false memories is that they have gaps in memory, which they try to fill with assumptions. The way this happens is affected by the environment and the mental state of the patient. For example, AD patients who have high neuroticism or depressive symptoms may have more negative false memories because neuroticism is a personality trait characterized by a tendency of individuals to experience negative emotions.
False memories are fabricated memories that are thought to have happened due to similar previous experiences (American Psychological Association). They are often very similar to reality, and AD patients have a hard time distinguishing between what is real and what is not. This is true even for healthy adults. For example, Elizabeth Loftus' TED Talk "How Reliable is Your Memory?" tells the story of Steve Titus, a man who was wrongfully convicted of a crime he did not commit. She explains that every year, many innocent people are falsely identified by eyewitnesses whose memories change after questioning (becoming false memories). She concludes that memories cannot always be trusted and can be manipulated. The incidence of false memories in AD patients is greater than in healthy adults. Budson et al. (2020) report that in AD patients, the prevalence of forgetting and false memory ranges from 69 to 96 percent and from 53 to 90 percent, respectively. This is compared to the corresponding 11 to 46 percent and 7 to 33 percent in healthy older adults. Based on a survey of clinicians and family members of patients, Turk et al. (2020) find that in AD patients, false memories happen as often as forgetting. False memories are so characteristic of AD patients that they may even be a useful indicator of AD, separate from the memory performance tests (Hildebrandt et al., 2009). The question that I want to investigate is: what are the cognitive mechanisms underlying false memory formation in Alzheimer's Disease? Understanding this helps suggest how the lives of patients suffering from Alzheimer’s Disease could be improved with cognitive interventions.
False memories are commonly studied by conducting Deese-Roediger-McDermott (DRM) experiments. Roediger and McDermott (1995) followed an earlier study by Deese by asking participants to recognize or recall related words (e.g., bed, rest, awake, tired, dream, etc.) associated with an omitted word (sleep), which served as a lure. The participants falsely recognized or recalled the lure words, although they were absent from the lists. This is consistent with the schema theory of organizing knowledge.
Figure 1: The word lists used in the experiment by Roediger and McDermott (1995).
False memories are attributed in literature to the inability of a person to monitor the source of the information/signal during retrieval (Roediger et al., 2001). AD patients struggle with distinguishing between external and internal stimuli. In the experiment, related concepts are activated during encoding, and individuals must monitor the source of these concepts during retrieval to distinguish between those that are actually presented and those that are internally generated. Another explanation for false memories is the fuzzy-trace theory. According to the theory, the mind records both verbatim (item-specific) and gist (general meaning) information at the same time. False memories are due to over-reliance on gist traces without specific information (Reyna & Brainerd, 1995). DRM testing for false memories revealed that, after many presentations, AD patients increased false recognition of lures, unlike healthy older adults and younger adults (Budson et al., 2000). This suggests that AD patients do not process the item-specific information with repetition but instead rely more on gist memory.
The classification of information verbatim (item-specific) and gist (general meaning) is perhaps related to the idea of two systems of thinking. In his popular science book “Thinking, Fast and Slow” psychologist Daniel Kahneman showed how emotions and logical reasoning are really two parts of the decision-making process, and neither of them dominates the other; they complement each other and work better in different situations (Kahneman, 2011). Kahneman distinguished between two systems of processing information and making decisions - Systems 1 and 2. System 1 thinking is fast, automatic, and intuitive. It is the “gut feeling” driven by instinct and past experiences. System 2 thinking is slower, more conscious, and logical. It requires more time and effort. The role of emotions is to enable people to make decisions when there is no time or no information to have more rational, logical decision-making using System 2 (for example, when one is in danger).
AD patients seem to rely on more primitive System 1 thinking, ignoring item-specific information. Emotional content may further complicate memory processes in AD patients by enhancing their reliance on gist memory (Fairfield et al., 2017). They also rely more on familiarity with an item rather than on recollection. Interestingly, in experiments, AD patients have a much higher chance of saying that something is familiar or old rather than new. For example, AD patients are more likely to endorse both studied and unstudied items as "old" compared to healthy older adults (Budson et al., 2006). This bias persists across various types of information (words and pictures) and recall times (Deason et al., 2012).
Figure 2: Images used in the experiment of Budson et al. (2006).
What factors affect memory processes in AD patients? El Haj et al. (2020) offer a comprehensive review of memory distortions in AD and provide explanations of how false memory forms in AD patients (the underlying cognitive mechanisms). They claim that memory characteristics such as a high emotional load, high vividness, or high familiarity make it more difficult for people with AD to suppress irrelevant (false) information. It is not surprising that emotions play an important role in memory formation and recall. Negative emotions promote sensory input (and System 1 thinking), while positive emotions often promote an interpretation of events (a slower System 2 thinking).
False memories are crucial in understanding Alzheimer's Disease. They arise from deficiencies in complex cognitive and neural functions of the brain. As AD patients attempt to fill in the gaps in their deteriorating memories, they rely more on gist memory, and this leads to the creation of false memories. Testing for false memory prevalence can be a diagnostic test at an early stage of AD development, allowing for early interventions. One way to fight false memories is to help patients distinguish between internal and external stimuli. Emotional regulation, such as stress reduction, is another way to do it because stress and other negative emotions hamper people’s ability to rely on System 2 thinking. Such cognitive interventions can potentially improve the quality of life for those affected by AD.
References
American Psychological Association. (n.d.). False memory. In APA Dictionary of Psychology. Retrieved November 13, 2024, from https://dictionary.apa.org/false-memory
Budson, A. E., Daffner, K. R., Desikan, R., & Schacter, D. L. (2000). When false recognition is unopposed by true recognition: Gist-based memory distortion in Alzheimer's disease. Neuropsychology, 14(2), 277-287. https://doi.org/10.1037/0894-4105.14.2.277
Budson, A. E., Todman, R. W., & Schacter, D. L. (2006). Gist memory in Alzheimer's disease: Evidence from categorized pictures. Neuropsychology, 20(1), 113-122. https://doi.org/10.1037/0894-4105.20.1.113
Budson, A., et al. (2020). False Memories: The Other Side of Forgetting. Boston University Medical Campus. Retrieved from https://www.bumc.bu.edu/camed/2020/02/28/false-memories-the-other-side-of-forgetting/
Deason, R. G., Hussey, E. P., Ally, B. A., & Budson, A. E. (2012). Changes in response bias with different study-test delays: Evidence from young adults, older adults, and patients with Alzheimer's disease. Neuropsychology, 26(1), 119-126. https://doi.org/10.1037/a0026330
Dewitt, M., & Schacter, D. L. (2018). False memories in patients with mild cognitive impairment due to Alzheimer’s disease. NCBI. Retrieved from https://pmc.ncbi.nlm.nih.gov/articles/PMC6399077/
El Haj, M., Colombel, F., Kapogiannis, D., & Gallouj, K. (2020). False Memory in Alzheimer's Disease. Behavioural neurology, 2020, 5284504. https://doi.org/10.1155/2020/5284504
Fairfield, B., Colangelo, M., Mammarella, N., Di Domenico, A., & Cornoldi, C. (2017). Affective false memories in Dementia of Alzheimer's Type. Psychiatry Research, 249, 9-15. https://doi.org/10.1016/j.psychres.2016.12.036
Hildebrandt, H., Haldenwanger, A., & Eling, P. (2009). False recognition helps to distinguish patients with Alzheimer's disease and amnestic MCI from patients with other kinds of dementia. Dementia and Geriatric Cognitive Disorders, 28(2), 159-167. https://doi.org/10.1159/000235643
National Institute on Aging. (2023, July 8). Alzheimer's Disease Fact Sheet. National Institutes of Health. https://www.nia.nih.gov/health/alzheimers-and-dementia/alzheimers-disease-fact-sheet
Kahneman, D. (2011). Thinking, fast and slow. Farrar, Straus and Giroux.
Kensinger E. A. (2009). Remembering the Details: Effects of Emotion. Emotion review: Journal of the International Society for Research on Emotion, 1(2), 99–113. https://doi.org/10.1177/1754073908100432
Loftus, E. (2013, September). How reliable is your memory? [Video]. TED Conferences. https://www.youtube.com/watch?v=PB2OegI6wvI
Reyna, V. F., & Brainerd, C. J. (1995). Fuzzy-trace theory: An interim synthesis. Learning and Individual Differences, 7(1), 1-75. https://doi.org/10.1016/1041-6080(95)90031-4
Roediger, H. L., Watson, J. M., McDermott, K. B., & Gallo, D. A. (2001). Factors that determine false recall: A multiple regression analysis. Psychonomic Bulletin & Review, 8(3), 385-407. https://doi.org/10.3758/BF03196177
Roediger, H. L., & McDermott, K. B. (1995). Creating false memories: Remembering words not presented in lists. Journal of Experimental Psychology: Learning, Memory, and Cognition, 21(4), 803-814. https://doi.org/10.1037/0278-7393.21.4.803
Turk, K. W., Palumbo, R., Deason, R. G., Marin, A., Elshaar, A., Gosselin, E., … Budson, A. E. (2020). False Memories: The Other Side of Forgetting. Journal of the International Neuropsychological Society, 26(6), 545–556. doi:10.1017/S1355617720000016
Image References
Roediger, H. L., & McDermott, K. B. (1995). Creating false memories: Remembering words not presented in lists. Journal of Experimental Psychology: Learning, Memory, and Cognition, 21(4), 803-814. https://doi.org/10.1037/0278-7393.21.4.803
Budson, A. E., Todman, R. W., & Schacter, D. L. (2006). Gist memory in Alzheimer's disease: Evidence from categorized pictures. Neuropsychology, 20(1), 113-122. https://doi.org/10.1037/0894-4105.20.1.113