My Attempt at Compiling SDAM's Symptoms & Features (Using Published Research)

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TL;DR - I created a simplified, introductory resource to SDAM’s documentation in scientific literature. Research available on the condition may be scarce, but still merits our support and recognition, especially since sustained public interest will hopefully fuel further scientific investigations.

Hello Everyone! I’m back again with another attempt at compiling SDAM-related documentation and research. This time I will focus mainly on research that is peer-reviewed and/or published in academic journals.

And in case you missed it, I previously attempted to document SDAM’s symptoms and features using posts from our subreddit as anecdotal evidence. You can read that post here - LINK

The list below focuses on major SDAM-related research findings with a link to every source. I have also included a sheet at the bottom of frequently used words and their definitions.

Note - This is not a conclusive list of research on SDAM, but it is a start at collecting documentation in a single easily accessible resource. I will also be updating this list with time, so please feel free to comment below with links to other published research articles the key takeaways gathered from it. Please also let me know if you notice any mistakes or potential correction so I can update this! Thank you!

Topics Below - In Order

General Topics / Introduction
Visual Imagery Deficits / Links Between SDAM & Aphantasia
Adaptations for SDAM
Biological Variations of SDAM
Standard Health & Mental Functioning
Variations in Health & Mental Functioning
Unanswered Question In Need of Further Research
Guide to Terms Used

General Topics / Introduction

SUMMARY	LINK
Those with Severely Deficient Autobiographical Memory (SDAM) are unable to vividly re-experience past events and have difficulty recalling specific episodic details, despite normal learning and memory for facts	LINK
SDAM causes profoundly impaired autobiographical re-experiencing in healthy adults.	LINK
Impared recovery of visual information	LINK

Visual Imagery Deficits / Links Between SDAM & Aphantasia

CATEGORIZATION	SUMMARY	LINK
DEFICIENT VISUALIZATION	Individuals with SDAM specifically report a lack of visual imagery during autobiographical memory retrieval	LINK
DEFICIENT VISUALIZATION	Patients with SDAM often report having poor visual imagery	LINK
DEFICIENT VISUALIZATION	Deficits in recollection may illustrate failures in relational binding of visual details to event information when being encoded. It could also reflect an inability to connect visual information with event cues during retrieval	LINK
DEFICIENT VISUALIZATION	Individuals with a lifetime reduction of visual imagery were likely to have corresponding deficits in autobiographical remembering	LINK
DEFICIENT VISUALIZATION	Studies on SDAM has helped contribute to the conclusion that autobiographical recall is dependent upon visual imagery	LINK

DEFICIENT VISUAL RECALL	SDAM cases’ have shown reductions in reliving of memories compared to control groups	LINK
DEFICIENT VISUAL RECALL	Due to the similar impairment on SDAM cases’ memory for visual source recall, and the importance of visual processes to autobiographical memory, the observed impairment can be mainly attributed to processing of visual information within autobiographical memory	LINK
DEFICIENT VISUAL RECALL	Deficits in recollection may illustrate failures in relational binding of visual details to event information when being encoded. It could also reflect an inability to connect visual information with event cues during retrieval	LINK

SDAM & APHANTASIA	Findings of visual-specific memory impairments in individuals with SDAM may suggest that Aphantasia and SDAM are overlapping syndromes	LINK

VISUALIZATION vs. DREAMS	Voluntary imagery differs from dreaming in that dreams originate from activity in the brain stem, whereas voluntary imagery is dependent upon the fronto-parietal cortical executive system. There is very little overlap between the two processes.	LINK

Adaptations for SDAM

CATEGORIZATION	SUMMARY	LINK
ACCOMMODATIONS & ADJUSTMENTS	Due to mnemonic alterations, those with SDAM may lack an emotional connection to their autobiographical experiences	LINK
ACCOMMODATIONS & ADJUSTMENTS	Mnemonic processes may assist SDAM patients with learning and retaining information in the absence of episodic processes	LINK
ACCOMMODATIONS & ADJUSTMENTS	Those with SDAM in particular may use strategies related to verbal and semantic memory in order to compensate for a lack of episodic recollection	LINK
ACCOMMODATIONS & ADJUSTMENTS	SDAM cases capacity to learn and retain information in the absence of episodic processes in turn suggests a mechanism by which they accomplish everyday tasks reliant on mnemonic processes	LINK
ACCOMMODATIONS & ADJUSTMENTS	Mnemonic processes may assist SDAM patients with learning and retaining information in the absence of episodic processes	LINK
ACCOMMODATIONS & ADJUSTMENTS	SDAM cases’ capacity to learn and retain information in the absence of episodic processes in turn suggests a mechanism by which they accomplish everyday tasks reliant on mnemonic processes	LINK
ACCOMMODATIONS & ADJUSTMENTS	Those with SDAM in particular may use strategies related to verbal and semantic memory in order to compensate for a lack of episodic recollection	LINK

Biological Variations of SDAM

CATEGORIZATION	SUMMARY	LINK
DEVELOPMENTAL DISORDER	Although it is unknown why people with SDAM lack the ability to recollect previously experienced events, it is suspected that the syndrome is developmental in nature.	LINK

NEUROIMAGING	The inability of SDAM patients to vividly recollect previously experienced events is supported by MRIs, ERPs, neural synchrony patterns associated with impaired episodic memory recollection and retrieval	LINK
NEUROIMAGING	Neuroimaging of SDAM cases’ revealed subtle reductions in the volume of the right hippocampal when contrasted to comparison participants. This portion of the brain is involved in recollection, specifically with processing non-verbal or visuospatial information	LINK
NEUROIMAGING	Structural neuroimaging revealed slight reductions in the volume of the right hippocampus, which is associated with the recollection of non-verbal/visual information.	LINK
NEUROIMAGING	fMRIs on SDAM patients showed reduced activation of brain regions involved in autobiographical memory.	LINK
NEUROIMAGING	Neuroimaging findings are consistent with visual mnemonic deficits	LINK
NEUROIMAGING	MRIs done on the hippocampus of SDAM cases shows right-lateralized reduced volume relative to control participants	LINK
NEUROIMAGING	Subtle reductions were identified in the right hippocampal volume of SDAM cases.	LINK
NEUROIMAGING	During retrieval of personally relevant episodic memories, SDAM patients show reduced activation in regions of the brain associated with episodic autobiographical memory (Regions of brain include midline regions including midline anterior posterior regions)	LINK
NEUROIMAGING	SDAM cases’ showed reduced activation in regions of the brain’s autobiographical memory network that were associated with various cognitive functions needed for mnemonic processes, including visuospatial imagery, familiarity and self-referential processes.	LINK
NEUROIMAGING	Activity reduction in the brain’s autobiographical memory network was notably seen in the Precuneus, a portion of the brain believed to mediate and link imagery associated with past events and connect them to mental representations of the one’s self	LINK
NEUROIMAGING	Reduced activation was observed in essential autobiographical memory regions that are critical for episodic memory formation, including right middle temporal gyrus, left medial temporal lobe and left thalamus.	LINK
NEUROIMAGING	SDAM patients showed reduced activation to autobiographical cues in regions thought to support visuo-spatial portions of autobiographical memory.	LINK
NEUROIMAGING	Activation reductions in the autobiographical memory network’s nodes have been linked to reduced self-referential processing, causing individuals with SDAM to potentially lack a first person, autonoetic consciousness to their past	LINK
NEUROIMAGING	It was found that brain activity, which is typical for reliving, is deficient during reconciliation for people with SDAM. This is further evidence that those with the condition are unable to unconsciously relive experiences.	LINK
NEUROIMAGING	Findings in individuals with SDAM suggest reduced task-based activation in critical nodes of the autobiographical memory network during autobiographical recollection	LINK
NEUROIMAGING	Findings suggest reduced engagement of the canonical autobiographical memory network for SDAM.	LINK

Standard Health & Mental Functioning

CATEGORIZATION	SUMMARY	LINK
STANDARD PERFORMANCE	SDAM cases show normal performance on neuropsychological tests of attention, perception, working memory, and executive function.	LINK
STANDARD PERFORMANCE	Patients with SDAM show normal performance when tested neuropsychologically on attention, perception, working memory, and executive function	LINK
STANDARD PERFORMANCE	Cases of SDAM demonstrate preservation in the ability to learn and retain factual (i.e., semantic) information, with deficits specifically impacting autobiographical memory.	LINK

COGNITIVE HEALTH	Those with SDAM cannot vividly recollect autobiographical experiences but are otherwise cognitively healthy.	LINK
COGNITIVE HEALTH	Similarities are shared between cases of SDAM and cases of developmental amnesia, with both featuring severely deficient episodic memories, yet relatively unaffected semantic memories. However, SDAM is distinct with individuals presenting as cognitively healthy and without any history of brain injury or imaging evidence of neuropathology	LINK

Variations in Health & Mental Functioning

CATEGORIZATION	SUMMARY	LINK
IMPAIRMENTS	The sole impairment of SDAM’s neuropsychological effects involves visual memory tasks. There is no evidence of verbal memory impairment.	LINK
IMPAIRMENTS	SDAM’s impairment specifically affected vivid visual episodic re-experiencing of personal events; however, it did not impact remembering personal semantics.	LINK
IMPAIRMENTS	SDAM patients were impaired relative to the controls in reporting spatiotemporally specific episodic details of remote events, but were still able to produce episodic details for recent events, albeit accompanied by significantly reduced vividness ratings across all time periods.	LINK
IMPAIRMENTS	SDAM patients score normally on most standard neuropsychological tests except for complex figure recall, with test scores that were “notable for impaired recovery of visual information”	LINK

DEFICIENT VISUAL IMAGERY	SDAM cases’ have shown reductions in reliving of memories compared to control groups	LINK
DEFICIENT AUDITORY IMAGERY	Deficits in auditory imagery are found in SDAM patients	LINK

Unanswered Question In Need of Further Research

Are SDAM and aphantasia (a lifelong deficit in visual imagery) related? It is suggested that the syndrome may be linked as individuals with aphantasia have reported difficulties with autobiographical memory?
Could the deficit of function memory/imagery in SDAM and aphantasia result in a paradoxical advantage for other mental functions such as improved logical reasoning or abstract processing of concepts?
Do genetics contribute to SDAM? Current research on genetic factors of autobiographical memory is lacking, but the limited memory studies available suggest a correlation?
What are the implications of aging with SDAM? Those with worse memory may be less susceptible to the effects of aging (which usually impacts episodic memory) due to prior development of alternative mnemonic strategies?

GUIDE TO TERMS USED ABOVE

WORD / TERM	DEFINITION
Severely Deficient Autobiographical Memory	A lifelong inability to vividly recollect or re-experience personal past events from a first-person perspective.
Autobiographical Memory	The memories of significant personal events and experiences from an individual's life.
Episodic Memory	The long-term ability to recall and mentally reexperience specific episodes, situations, and experiences. and events from one's personal past.
Semantic Memory	The long-term ability to recall words, numbers, or concepts that are not drawn from personal experience and that are essential for the use and understanding of language.
Mnemonic	A tool such as ideas, songs, rhymes, acronyms, images, associations, or a pattern of letters that assists in remembering something such as certain facts or large amounts of information.
Visual Spatial Imagery	Ability to mentally visualize spatial locations, relations, and transformations
Relational Binding	Memory binding function that supports the retention of the links between memory items (e.g., objects and locations, faces and names)
Survey of Autobiographical Memory	Survey regarding an individual’s interpretation of their own autobiographical memory abilities, resulting in Episodic, Spatial, Future, Semantic, and Total Autobiographical memory scores.

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WanderingWombats

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