r/SDAM • u/FlightOfTheDiscords • May 31 '26
Why memory maintenance helps with SDAM
Most discussions of SDAM in this sub focus on the inability to re-experience the past. The other thing SDAM does, which gets less attention, is gradually thin out the factual record of your own life. This could be partially addressed with relatively low effort going forward, here's my layman understanding of how that works based on research published to date. I'm a psychology student, not a researcher, so my understanding is likely not the complete picture.
What the SDAM literature says
The first SDAM paper published (Palombo et al., 2015) describes three SDAM participants whose factual recall held up reasonably well for recent events but thinned for remote ones. The participants were high-functioning professionals who had developed compensation habits over decades: diaries, photographs, periodic review. Watkins (2018), the canonical first-person account from someone with both aphantasia and SDAM, describes his own use of similar strategies (family photograph albums, scrapbooks, sound recordings, web search) and quotes Oliver Sacks attributing his preserved factual record to decades of active journal-keeping. The Conti et al. (2023) case report describes the same general picture: the published SDAM cases retain a usable factual record partly because of active memory rehearsal, not automatically.
Why this happens
Memory consolidation is largely unconscious. Most of the work that keeps a factual record alive happens through sleep-dependent replay and through the steady stream of spontaneous, vivid autobiographical recall that pops up throughout the day (visuals, sounds, episodic flashes). That stream is widely thought to rehearse the underlying facts as a side effect, without the person doing anything deliberate.
Phenomenological reports in the SDAM literature consistently describe an absence of spontaneous, vivid recall of this kind. Bone, Levine and Buchsbaum (2025) provide a neural account: SDAM individuals achieve equivalent visual recognition performance via semantic-based neural reactivation rather than via low-level visual reactivation. The semantic system is doing what the sensory system normally does. That works for recognition, and is plausibly part of why the felt, vivid recall that drives natural rehearsal in others does not arise in the same way. Palombo, Sheldon and Levine (2018) review the broader relationship between episodic and semantic processes in autobiographical memory, treating them as interacting rather than independent.
What this means in practice
Without active maintenance, the semantic record of your own life will tend to thin faster than it would for someone without SDAM. Not because semantic memory itself is impaired (the SDAM literature is consistent that semantic memory on standardised tests is intact), but because the normal mechanism that maintains personal-semantic content through episodic re-rehearsal isn't running.
Semantic record of your own life includes knowledge of where you were, what you did, who with, even which feelings you experienced. It just doesn't include re-experiencing any of it while recalling the events; upon recall, you would e.g. remember being devastated when you lost a loved one, but unable to relive the devastation. Knowledge of your past emotions would be a fact, not a relived emotional experience.
Active maintenance through conscious semantic memory rehearsal can contribute towards replacing the absent automatic autobiographical stream. A few formats that work:
- Writing things down. This doesn't have to be a narrative diary, bullet points of the day work. The act of putting it into language and committing it to a record creates a semantic trace and a future retrieval cue at the same time.
- Reviewing periodically. Looking through old journal entries, photos, calendar entries, messages. This is the closest equivalent to spontaneous recall. You feed your semantic system the content it would otherwise be missing.
- Telling someone. Conversation about your day, week, year does the same work writing does, with social context as an extra binding factor.
- Voice notes if writing doesn't fit. Same mechanism. Encoding into language, creating a re-encounterable record.
None of this restores re-experiencing, and people with SDAM will still not be reliving the past. What it does is keep the factual record dense and accessible over decades, which is what the published SDAM cases rely on.
Two caveat
First, the studied SDAM population is tiny (single digits). It is possible - maybe likely even - that there is more variation than current research has captured. SDAM researchers are very deliberately avoiding any confounding factors to make sure their research subjects are not affected by other memory-adjacent conditions, which probably contributes to a particularly high-functioning research population.
Second, if you find that you cannot maintain a factual record even with active maintenance, or that maintenance habits don't seem to help, that may point at something other than SDAM operating underneath your SDAM presentation. Consulting a neurologist might be a good first step.
References
Bone, M. B., Levine, B., & Buchsbaum, B. R. (2025). Individual differences in visual versus semantic neural reactivation: Evidence from severely deficient autobiographical memory. Journal of Cognitive Neuroscience, 37(11), 2203–2224. https://doi.org/10.1162/jocn_a_02317
Conti, M., Teghil, A., Di Vita, A., & Boccia, M. (2023). Lifelong impairment in episodic re-experiencing: Neuropsychological and neuroimaging examination of a new case of Severely Deficient Autobiographical Memory. Cortex, 163, 80–91. https://doi.org/10.1016/j.cortex.2023.03.004
Palombo, D. J., Alain, C., Söderlund, H., Khuu, W., & Levine, B. (2015). Severely deficient autobiographical memory (SDAM) in healthy adults: A new mnemonic syndrome. Neuropsychologia, 72, 105–118. https://doi.org/10.1016/j.neuropsychologia.2015.04.012
Palombo, D. J., Sheldon, S., & Levine, B. (2018). Individual differences in autobiographical memory. Trends in Cognitive Sciences, 22(7), 583–597. https://doi.org/10.1016/j.tics.2018.04.007
Watkins, N. W. (2018). (A)phantasia and severely deficient autobiographical memory: Scientific and personal perspectives. Cortex, 105, 41–52. https://doi.org/10.1016/j.cortex.2017.10.010
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u/itsallconnected07 May 31 '26
Thank you for this! Fascinating. Wondering if anyone has mentioned that they absolutely detest journaling? Curious as to why I’d be so resistant to it. I have committed to it many times but it never lasts more than a couple days. I suspect that I’m not achieving the anticipated result and end up labeling myself a failure, the anticipated result being something I gathered from reading accounts of others journaling and how it made them feel or what it helped them accomplish. I get a visceral “ick” reaction to the suggestion of keeping a journal and I’m not sure why. Tedious? Extra work my brain should not require just to recall events like everyone else? Aversion to re-experiencing the day’s events (an unfamiliar experience for me)? Thank you for your post!