Aging impacts memory for perceptual,but not narrative,event details

Memory is well known to decline over the course of healthy aging. However, memory is not a monolith and draws from different kinds of representations. Historically, much of our understanding of age-related memory decline stems from recognition of isolated studied items. In contrast, real-life events are often remembered as narratives, and this kind of information is generally missed in typical recognition memory studies. Here, we designed a task to tax mnemonic discrimination of event details, directly contrasting perceptual and narrative memory. Older and younger adults watched an episode of a television show and later completed an old/new recognition test featuring targets, novel foils, and similar lures in narrative and perceptual domains. While we observed no age-related differences on basic recognition of repeated targets and novel foils, older adults showed a deficit in correctly rejecting perceptual, but not narrative, lures. These findings provide insight into the vulnerability of different memory domains in aging and may be useful in characterizing individuals at risk for pathological cognitive decline.

Memory decline is among the most commonly reported cognitive changes with aging (Craik 1994; Bäckman et al. 2001; Salthouse 2003). In particular, older adults appear to show marked decline in the ability to support episodic memories for specific events and instances (Nilsson 2003; Salthouse 2003; Hedden and Gabrieli 2004). Older adults reliably show deficits when freely recalling studied information (Craik and McDowd 1987; Gutchess et al. 2006) or remembering specific item–context pairings (Old and Naveh-Benjamin 2008; Craik et al. 2010). In contrast, older adults do not consistently show deficiencies in old/new recognition memory. This and related evidence have led to the view that older adults have preserved memory for gist, but loss of specific details (Schacter et al. 1997; Abadie et al. 2021; Grilli and Sheldon 2022). That is, older adults tend to remember a general understanding of the overall experience but are disadvantaged at maintaining precise, high-fidelity details (Radvansky et al. 2001). However, it is not well understood whether such relative loss of detailed memory extends across information domains.The Mnemonic Similarity Task (MST) is a recognition paradigm that is specifically designed to tax high-fidelity memory representations (Kirwan and Stark 2007; Stark et al. 2013, 2019). MST performance depends on maintaining similar representations in memory as distinct and nonoverlapping (Yassa and Stark 2011). This is thought to rely on pattern separation in the hippocampus (McClelland et al. 1995; Norman and O''Reilly 2003; Leutgeb et al. 2007; Bakker et al. 2008), a process that is strongly impacted in the aging brain (Wilson et al. 2006; Burke et al. 2010). Typical MST paradigms involve an incidental encoding task, such as making indoor or outdoor judgments for pictures of everyday objects, and then a surprise recognition memory test. In the memory test, participants are tasked to identify exact repetitions of previously encoded objects (targets), new objects (foils), and objects that are perceptually similar to images encountered during the encoding task (lures) as old or new. Older adults are more likely to endorse similar lures as previously studied items (Toner et al. 2009; Holden et al. 2013), which correlates with aberrant structural and functional properties of the human hippocampus and surrounding cortical regions (Yassa et al. 2011a; Reagh et al. 2018). The MST therefore offers mechanistic insights into high-fidelity recognition-based memory in the human brain.Nonetheless, studies using the MST have often limited their scope to detecting visual changes among isolated items. Other recognition studies that have incorporated discrimination of highly similar information in more complex formats, such as source memory discrimination, also report age-related deficits (Schacter et al. 1991; Chalfonte and Johnson 1996; Naveh-Benjamin et al. 2003; Dennis et al. 2008). For instance, older adults had difficulty assessing the source of a word when it originated from two female speakers compared with across gender speakers (Ferguson et al. 1992). These studies, however, largely assess recognition memory processes for isolated items—snapshots of perceptual experience in the context of a laboratory experiment. Moreover, there is growing evidence that aging does not equally impact all domains of information that are involved in constructing a memory. For instance, recent work suggests that aging distinctly influences medial temporal lobe circuits underlying memory for items versus contexts or space (Reagh et al. 2016, 2018; Berron et al. 2018).Real-world memories are not made of isolated pieces of information, but instead are structured and bridged together by meaning (Schank 1975; Conway and Rubin 2019; Cohn-Sheehy et al. 2022). Prior studies have shown that older adults are relatively impaired at detecting and remembering perceptual changes in everyday events, suggesting that basic findings from MST paradigms likely translate to real-world deficits (Wahlheim and Zacks 2019). However, a critical component of human memory is information about narratives, whether autobiographical or fictional (Radvansky et al. 2005; León 2016). Narratives tend to be organized to follow an ideal internal structure that can be relied on (Mandler and Johnson 1977; Thorndyke 1977). Studies that use narratives to test memory typically task participants with recalling information from a story or event. This has led to the idea that aging impacts recall more drastically than recognition (Danckert and Craik 2013). Interestingly, similar to studies of recognition memory, recall performance in aging has been characterized by loss of specific details and emphasis on information that capture the central idea of an experience (Addis et al. 2008). This may be due to the unconstrained nature of recall tasks or because self-initiated recall may be more taxing for older adults. Thus, the extent to which narrative details are truly lost versus not voluntarily retrieved in aging remains unclear. In line with this idea, tasks designed to drive participants to recall events in terms of specific details have shown enhancement effects in older adults (Madore et al. 2014). To our knowledge, however, there has not been an investigation into whether recognition of highly specific narrative details is affected in aging similarly to perceptual details.Testing of narrative and perceptual domains alongside one another in a controlled and highly similar way allows us to gain a better understanding into the processing of different types of information in memory. Memory is not a unitary phenomenon, and memory performance can often be based on multiple processes and types of representations. This approach offers unique insights into the aging brain, as it has been previously proposed that information about narratives and situations may be preferentially encoded differently in distinct cortical pathways to the hippocampus compared with more perceptually focused information (Ranganath and Ritchey 2012; Reagh and Ranganath 2018). Other emerging neural evidence suggests that specific networks specialize in cognitive processes that are relevant for gist and detailed memory (Robin and Moscovitch 2017; Sekeres et al. 2018). Given that these brain networks may be distinctly vulnerable to age-related pathologies (Jagust 2018; Maass et al. 2019), these insights may further offer us clues into pathological aging.Here, we designed a task to simultaneously tax mnemonic discrimination in perceptual and narrative domains. This task is analogous to traditional MST paradigms composed of an incidental encoding task followed by a recognition test. However, with the goal of tapping into mechanisms involved in encoding of the meaningful, continuous, and dynamic world that we live in, the incidental encoding task consists of watching a television sitcom (HBO''s Curb Your Enthusiasm, S01E07: “AAMCO”) (see Fig. 1A). Television shows offer a unique methodology that balances realistic scenarios while directing our attention to specific perceptual and narrative details. After encoding, participants completed an old/new recognition test featuring targets, foils, and similar lures in the perceptual domain, as well as a novel variant testing mnemonic discrimination of narrative details. This allowed us to test detailed memory for perceptual and narrative information using an ecologically valid yet constrained approach. That is, encoding involves an immersive stimulus that hinges on meaningful and nonarbitrary narrative organization. Additionally, although retrieval is akin to a standard recognition test, it assesses memory along two dimensions that may provide insight into how we process different memory representations for lifelike events. Unlike prior studies testing narrative understanding, here we critically tested narrative memory in terms of basic recognition (targets and foils) as well as high-fidelity narrative details (lures). Performance was compared across younger and older adults for both information domains.Open in a separate windowFigure 1.(A) Participants viewed a 26-min episode of a sitcom. (B) Old/new recognition task based on narrative or perceptual details, with order of test domain counterbalanced across participants. Each recognition task consisted of 30 targets (described or depicted moments from the video encoded), similar lures (moments described or depicted as being similar to the video encoded), and novel foils (described or depicted moments not from the video encoded).We predicted no differences in basic recognition of repeated targets and novel foils across age groups based on prior MST results (Stark et al. 2013, 2019; Toner et al. 2009; Holden et al. 2013). In line with prior work showing decreased performance in perceptual lures among older adults (Toner et al. 2009; Holden et al. 2013; Stark et al. 2013, 2019), we further predicted greater age-related deficits in perceptual lure discrimination than narrative lure discrimination. Relatively intact memory for narrative details may reflect being able to rely on narrative structure or the meaning of events.     

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