Individual differences in autobiographical memory and SDAM
Replication of the latent structure of the Survey of Autobiographical memory (SAM) in 7487 individuals (Fan, Abdi, & Levine, 2020)
Some people remember events vividly while others have only a vague recollection of the same events. Similarly, some efficiently access factual information, such as news events or trivia, whereas others do not. Few studies have investigated such individual differences in naturalistic memory, although there have been studies concerning individual differences in performance on laboratory tasks. We have been studying "trait mnemonics" as individual differences – much like personality traits – that may have implications for cognitive function (for review, see Palombo et al, 2018). This work was inspired by the discovery of Severely Deficient Autobiographical Memory (SDAM), a syndrome whereby healthy adults report an inability to re-experience personal past events.
The Survey of Autobiographical Memory (SAM; Palombo et al., 2013)
Whereas the AI assesses performance (quantified detail recovery) for discrete and typically self-selected events, the Survey of Autobiographical Memory (SAM; Palombo et al., 2013) assesses the degree to which one retrieves and subjectively re-experiences personal past episodes in general. The SAM also includes subscales for semantic memory (i.e., how easily one learns and retains general factual information), spatial navigational ability, and future thinking. The latent structure of the SAM has been replicated by our group (Fan, Abdi, and Levine, 2020) and others (Picco et al., 2020). In the past 10 years, our group and others have used the SAM as an individual differences measure to explore the relationships of trait mnemonics to other cognitive processes (visual imagery, conceptual reasoning).
Click here for a full list of studies using the SAM.
The Survey of Autobiographical Memory (SAM; Palombo et al., 2013)
Whereas the AI assesses performance (quantified detail recovery) for discrete and typically self-selected events, the Survey of Autobiographical Memory (SAM; Palombo et al., 2013) assesses the degree to which one retrieves and subjectively re-experiences personal past episodes in general. The SAM also includes subscales for semantic memory (i.e., how easily one learns and retains general factual information), spatial navigational ability, and future thinking. The latent structure of the SAM has been replicated by our group (Fan, Abdi, and Levine, 2020) and others (Picco et al., 2020). In the past 10 years, our group and others have used the SAM as an individual differences measure to explore the relationships of trait mnemonics to other cognitive processes (visual imagery, conceptual reasoning).
Click here for a full list of studies using the SAM.
Episodic autobiographical memory related to posterior MTL connectivity (warm colors), semantic ability related to anterior MTL connectivity (cool colors)
Neural correlates of trait mnemonics
Sheldon et al (2016) demonstrated that individual differences in trait mnemonics as measured by the SAM are related to intrinsic functional connectivity as measured by resting state functional MRI (i.e., brain activity in the absence of overt task demands). Endorsement of strongly vivid episodic memory was associated with increased connectivity between the medial temporal lobes and posterior regions. That is, individuals who report high episodic autobiographical memory in their day-to-day lives show increased connectivity in memory networks involved in accessing images and other perceptual information. Endorsement of high factual or semantic memory showed a different pattern: enhanced connectivity between the medial temporal lobes and prefrontal regions involved in organization and integrating conceptual information. Using a larger external sample (from the Human Connectome Project; HCP) with contemporaneous fMRI and behavioral performance data, we found that trait subjective episodic vividness related to neural patterns associated with perceptual processes, whereas self-rated semantic abilities corresponded to neural patterns associated with gist-based processing (Petrican & Levine, 2020). These findings suggest that individual differences in memory states as rated by the SAM relate to stable differences in functional brain organization.
Sheldon et al (2016) demonstrated that individual differences in trait mnemonics as measured by the SAM are related to intrinsic functional connectivity as measured by resting state functional MRI (i.e., brain activity in the absence of overt task demands). Endorsement of strongly vivid episodic memory was associated with increased connectivity between the medial temporal lobes and posterior regions. That is, individuals who report high episodic autobiographical memory in their day-to-day lives show increased connectivity in memory networks involved in accessing images and other perceptual information. Endorsement of high factual or semantic memory showed a different pattern: enhanced connectivity between the medial temporal lobes and prefrontal regions involved in organization and integrating conceptual information. Using a larger external sample (from the Human Connectome Project; HCP) with contemporaneous fMRI and behavioral performance data, we found that trait subjective episodic vividness related to neural patterns associated with perceptual processes, whereas self-rated semantic abilities corresponded to neural patterns associated with gist-based processing (Petrican & Levine, 2020). These findings suggest that individual differences in memory states as rated by the SAM relate to stable differences in functional brain organization.
DVN interference effect is correlated with spatial imagery abilities
Experimental evidence
One way to study memory abilities is to manipulate or interfere with them in an experiment. Sheldon et al (2016) tested memory for video stimuli while participants were watching a screen with Dynamic Visual Noise (DVN) or a solid grey screen. DVN interferes with the ability to form images. We also asked participants to rate their visual imagery abilities on a questionnaire. Individual differences in visual imagery abilities interacted with DVN such that the higher one's visual imagery ratings, the greater the effect of DVN. In other words, individuals who readily form visual images showed greater interference effects during DVN, whereas those who with lower visual imagery abilities were less affected by this manipulation. This study reinforces a link between visual imagery and memory.
One way to study memory abilities is to manipulate or interfere with them in an experiment. Sheldon et al (2016) tested memory for video stimuli while participants were watching a screen with Dynamic Visual Noise (DVN) or a solid grey screen. DVN interferes with the ability to form images. We also asked participants to rate their visual imagery abilities on a questionnaire. Individual differences in visual imagery abilities interacted with DVN such that the higher one's visual imagery ratings, the greater the effect of DVN. In other words, individuals who readily form visual images showed greater interference effects during DVN, whereas those who with lower visual imagery abilities were less affected by this manipulation. This study reinforces a link between visual imagery and memory.
Relationship to other visual and spatial processes
The link between different forms of autobiographical memory as assessed by the SAM and visual imagery was reinforced in a study of 7,487 volunteers, led by Carina Fan. Episodic autobiographical memory and spatial navigation dissociated from each other and mapped onto different forms of visual imagery (Fan, Abdi, & Levine, 2020), a finding that runs counter to theories that tightly link episodic memory and navigation.
The link between different forms of autobiographical memory as assessed by the SAM and visual imagery was reinforced in a study of 7,487 volunteers, led by Carina Fan. Episodic autobiographical memory and spatial navigation dissociated from each other and mapped onto different forms of visual imagery (Fan, Abdi, & Levine, 2020), a finding that runs counter to theories that tightly link episodic memory and navigation.
Relationships between the SAM subscales and imagery as measured by the Object-Spatial Imagery Questionnaire (OSIQ; Blajenkova et al., 2006) in 7487 adults. The SAM-episodic and SAM-future subscales are related to object-scene imagery, whereas the SAM-spatial subscale is related to the spatial imagery. From Fan, Abdi, & Levine, 2020)
Eye movements (number of fixations) relate to the number of internal (episodic) details recalled for a staged event but only for those high (left) trait-level episodic autobiographical memory (as measured by the SAM; Armson et al., 2020). As fixations are an oculomotor indicator of visual imagery, these findings suggest that those with high episodic autobiographical memory experience a greater degree of visual vividness than those with low episodic autobiographical memory. External (non-episodic) details were unrelated to fixations.
Visual processes: eye movement monitoring
In collaboration with Rotman scientist Jennifer Ryan, Mike Armson assessed visual processes through objective measures derived from eye movement monitoring. Participants recalled events while their eye movements upon a blank screen were monitored. Consistent with the notion that autobiographical memory involves visual imagery, we found that saccades were related to the richness of memory as quantified by internal (but not external) details on the Autobiographical Interview. However, under an individual differences framework, we reasoned that this relationship would be modulated by trait episodic autobiographical capacities. Evidence for this hypothesis was supported through free recall of a staged event across 90 participants with varying episodic autobiographical memory capacities as measured by the SAM (Armson, Ryan, & Levine, 2020). This finding suggests that those with congenitally lower episodic autobiographical memory abilities (such as people with SDAM; see below) generate internal episodic details via non-visual mechanisms, such as implicational reasoning, converging with the brain image analysis results of Sheldon and colleagues (2016) and Petrican & Levine, (2020; see above).
In collaboration with Rotman scientist Jennifer Ryan, Mike Armson assessed visual processes through objective measures derived from eye movement monitoring. Participants recalled events while their eye movements upon a blank screen were monitored. Consistent with the notion that autobiographical memory involves visual imagery, we found that saccades were related to the richness of memory as quantified by internal (but not external) details on the Autobiographical Interview. However, under an individual differences framework, we reasoned that this relationship would be modulated by trait episodic autobiographical capacities. Evidence for this hypothesis was supported through free recall of a staged event across 90 participants with varying episodic autobiographical memory capacities as measured by the SAM (Armson, Ryan, & Levine, 2020). This finding suggests that those with congenitally lower episodic autobiographical memory abilities (such as people with SDAM; see below) generate internal episodic details via non-visual mechanisms, such as implicational reasoning, converging with the brain image analysis results of Sheldon and colleagues (2016) and Petrican & Levine, (2020; see above).
Functional implications of trait autobiographical memory in aging
Individual differences in trait mnemonics may also have implications for how people function as they age. Although memory decline is a hallmark of normal aging, we predicted that people with congenitally lower episodic memory abilities may actually function better as they age compared to people who have been used to relying on their strong episodic memory throughout life and must newly adapt to age-related decline. We found evidence for this hypothesis in a cross-sectional online study of almost 1000 older adults (Fan, Romero, & Levine, 2020), and we are currently preparing for a longitudinal follow-up study to assess if this effect holds over time.
Individual differences in trait mnemonics may also have implications for how people function as they age. Although memory decline is a hallmark of normal aging, we predicted that people with congenitally lower episodic memory abilities may actually function better as they age compared to people who have been used to relying on their strong episodic memory throughout life and must newly adapt to age-related decline. We found evidence for this hypothesis in a cross-sectional online study of almost 1000 older adults (Fan, Romero, & Levine, 2020), and we are currently preparing for a longitudinal follow-up study to assess if this effect holds over time.
People with low episodic autobiographical memory abilities as measured by the SAM report greater real-life memory errors and slips in their 50's, but not with advancing age, suggesting that they are better equipped to resist age-related memory changes than those with congenitally higher episodic autobiographical memory abilities (from Fan et al., 2020).
Severely Deficient Autobiographical Memory (SDAM)
SDAM refers to a lifelong inability to vividly relive or re-experience personal events. Palombo and colleagues (2015) report data from three healthy, high functioning individuals with SDAM and matched controls intensively studied in our laboratory. We found that these individuals had reduced visual memory on laboratory tasks, reduced right hippocampal volume, and reduced activation of the canonical autobiographical memory network during fMRI scanning. They also showed a greatly reduced late positivity Event Related Potential (ERP) component of recognition memory for pictures presented in a laboratory experiment, in spite of the fact that their recognition memory performance was intact. The late positivity ERP component indicates conscious recollection or re-experiencing of the test item. This latter finding suggests that intact memory performance (and day-to-day memory function) in SDAM is may be supported by non-episodic processes (e.g., semantic memory, familiarity).
In a followup study, Fuentemilla, Palombo, and Levine (2018) played recordings of prospectively collected autobiographical events during monitoring of brain activity with magnetoencephalography (MEG), which directly measures brain activity. Healthy adults showed robust synchronized oscillations in the gamma frequency (27-45 Hz) when listening to these recordings, whereas an individual with SDAM did not, although normal activity was observed in relation to stimulation with semantic information.
We have been contacted by many thousands of individuals since our initial publication concerning SDAM and subsequent media presentations who have volunteered for research by completing our online memory survey. More information about SDAM can be found here.
SDAM refers to a lifelong inability to vividly relive or re-experience personal events. Palombo and colleagues (2015) report data from three healthy, high functioning individuals with SDAM and matched controls intensively studied in our laboratory. We found that these individuals had reduced visual memory on laboratory tasks, reduced right hippocampal volume, and reduced activation of the canonical autobiographical memory network during fMRI scanning. They also showed a greatly reduced late positivity Event Related Potential (ERP) component of recognition memory for pictures presented in a laboratory experiment, in spite of the fact that their recognition memory performance was intact. The late positivity ERP component indicates conscious recollection or re-experiencing of the test item. This latter finding suggests that intact memory performance (and day-to-day memory function) in SDAM is may be supported by non-episodic processes (e.g., semantic memory, familiarity).
In a followup study, Fuentemilla, Palombo, and Levine (2018) played recordings of prospectively collected autobiographical events during monitoring of brain activity with magnetoencephalography (MEG), which directly measures brain activity. Healthy adults showed robust synchronized oscillations in the gamma frequency (27-45 Hz) when listening to these recordings, whereas an individual with SDAM did not, although normal activity was observed in relation to stimulation with semantic information.
We have been contacted by many thousands of individuals since our initial publication concerning SDAM and subsequent media presentations who have volunteered for research by completing our online memory survey. More information about SDAM can be found here.