Shift happens: aging alters the content but not the organization of memory for complex events.

While cognitive aging research has compared episodic memory accuracy between younger and older adults, less work has described differences in how memories are encoded and recalled. This is important for memories of real-world experiences, since there is immense variability in which details can be accessed and organized into narratives. We investigated age effects on the organization and content of memory for complex events. In two independent samples (N = 45; 60), young and older adults encoded and recalled the same short-movie. We applied a novel scoring on the recollections to quantify recall accuracy, temporal organization (temporal contiguity, forward asymmetry), and content (perceptual, conceptual). No age-effects on recall accuracy nor on metrics of temporal organization emerged. Older adults provided more conceptual and non-episodic content, whereas younger adults reported a higher proportion of event-specific information. Our results indicate that age-related differences in episodic recall reflect distinctions in what details are assembled from the past.

Some young adults hyper-bind too: Attentional control relates to individual differences in hyper-binding.

Hyper-binding - the erroneous encoding of target and distractor information into associative pairs in memory - has been described as a unique age effect caused by declines in attentional control. Previous work has found that, on average, young adults do not hyper-bind. However, if hyper-binding is caused by reduced attentional control, then young adults with poor attention regulation should also show evidence of hyper-binding. We tested this question with an individual differences approach, using a battery of attentional control tasks and relating this to individual differences in hyper-binding. Participants (N = 121) completed an implicit associative memory test measuring memory for both target-distractor (i.e., hyper-binding) and target-target pairs, followed by a series of tasks measuring attentional control. Our results show that on average, young adults do not hyper-bind, but as predicted, those with poor attentional control show a larger hyper-binding effect than those with good attentional control. Exploratory analyses also suggest that individual differences in attentional control relate to susceptibility to interference at retrieval. These results support the hypothesis that hyper-binding in older adults is due to age-related declines in attentional control, and demonstrate that hyper-binding may be an issue for any individual with poor attentional control, regardless of age.

Ensemble coding of facial identity is robust, but may not contribute to face learning.

Ensemble coding - the rapid extraction of a perceptual average - has been proposed as a potential mechanism underlying face learning. We tested this proposal across five pre-registered experiments in which four ambient images of an identity were presented in the study phase. In Experiments 1 and 2a-c, participants were asked whether a test image was in the study array; these experiments examined the robustness of ensemble coding. Experiment 1 replicated ensemble coding in an online sample; participants recognize images from the study array and the average of those images. Experiments 2a-c provide evidence that ensemble coding meets several criteria of a possible learning mechanism: It is robust to changes in head orientation (± 60o), survives a short (30s) delay, and persists when images of two identities are interleaved during the study phase. Experiment 3 examined whether ensemble coding is sufficient for face learning (i.e., facilitates recognition of novel images of a target identity). Each study array comprised four ambient images (variability + average), a single image, or an average of four images (average only). Participants were asked whether a novel test image showed the identity from a study array. Performance was best in the four-image condition, with no difference between the single-image and average-only conditions. We conclude that ensemble coding of facial identity is robust but that the perceptual average per se is not sufficient for face learning.

The yeast molecular chaperone, Hsp104, influences transthyretin aggregate formation.

Patients with the fatal disorder Transthyretin Amyloidosis (ATTR) experience polyneuropathy through the progressive destruction of peripheral nervous tissue. In these patients, the transthyretin (TTR) protein dissociates from its functional tetrameric structure, misfolds, and aggregates into extracellular amyloid deposits that are associated with disease progression. These aggregates form large fibrillar structures as well as shorter oligomeric aggregates that are suspected to be cytotoxic. Several studies have shown that these extracellular TTR aggregates enter the cell and accumulate intracellularly, which is associated with increased proteostasis response. However, there are limited experimental models to study how proteostasis influences internalized TTR aggregates. Here, we use a humanized yeast system to recapitulate intracellular TTR aggregating protein in vivo. The yeast molecular chaperone Hsp104 is a disaggregase that has been shown to fragment amyloidogenic aggregates associated with certain yeast prions and reduce protein aggregation associated with human neurogenerative diseases. In yeast, we found that TTR forms both SDS-resistant oligomers and SDS-sensitive large molecular weight complexes. In actively dividing cultures, Hsp104 has no impact on oligomeric or large aggregate populations, yet overexpression of Hsp104 is loosely associated with an increase in overall aggregate size. Interestingly, a potentiating mutation in the middle domain of Hsp104 consistently results in an increase in overall TTR aggregate size. These data suggest a novel approach to aggregate management, where the Hsp104 variant shifts aggregate populations away from toxic oligomeric species to more inert larger aggregates. In aged cultures Hsp104 overexpression has no impact on TTR aggregation profiles suggesting that these chaperone approaches to shift aggregate populations are not effective with age, possibly due to proteostasis decline.

Looking the same, but remembering differently: Preserved eye-movement synchrony with age during movie watching.

Naturalistic stimuli (e.g., movies) provide the opportunity to study lifelike experiences in the lab. While young adults respond to these stimuli in a highly synchronized manner [as indexed by intersubject correlations (ISC) in their neural activity], older adults respond more idiosyncratically. Here, we examine whether eye-movement synchrony (eye-ISC) also declines with age during movie-watching and whether it relates to memory for the movie. Our results show no age-related decline in eye-ISC, suggesting that age differences in neural ISC are not caused by differences in viewing patterns. Both age groups recalled the same number of episodic details from the movie, but older adults recalled proportionally fewer episodic details due to their greater output of semantic and false information. In both age groups, higher eye-ISC related to a higher proportion of internal details and a lower proportion of false information being recalled. Finally, both older and younger adults showed better cued recall for cues taken from within the same event than those spanning an event boundary, further confirming that events are stored in long-term memory as discrete units with stronger associations within than across event boundaries. Taken together, these findings suggest that naturalistic stimuli drive perception in a similar way in younger and older adults, but age differences in neural synchrony further up the information processing stream may contribute to subtle differences in event memory. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Implicit associative memory remains intact with age and extends to target-distractor pairs.

In this study, we use a novel, implicit memory paradigm to test forhyper-binding, or older adults' tendency to form non-target associations. Participants viewed pictures of objects superimposed with text and made speeded categorization judgments about the objects across three blocks varying in binding demand. During the no- and some-binding blocks, participants decided if the pictured object alone could fit inside a drawer while ignoring superimposed non-words and words, respectively. During the full-binding block, participants decided if both items could fit inside a drawer together. At test, participants viewed intact and rearranged pairs from encoding and decided if both items could fit in a drawer together. Across two experiments, older adults responded faster to intact than rearranged pairs from both the some- and full-binding blocks, while young adults showed no difference in RTs. These findings suggest that implicit associative memory is preserved with age and extends to non-target information.

Ensemble coding of facial identity is not refined by experience: Evidence from other-race and inverted faces.

The ability to recognize identity despite within-person variability in appearance is likely a face-specific skill and shaped by experience. Ensemble coding - the automatic extraction of the average of a stimulus array - has been proposed as a mechanism underlying face learning (allowing one to recognize novel instances of a newly learned face). We investigated whether ensemble encoding, like face learning and recognition, is refined by experience by testing participants with upright own-race faces and two categories of faces with which they lacked experience: other-race faces (Experiment 1) and inverted faces (Experiment 2). Participants viewed four images of an unfamiliar identity and then were asked whether a test image of that same identity had been in the study array. Each test image was a matching exemplar (from the array), matching average (the average of the images in the array), non-matching exemplar (a novel image of the same identity), or non-matching average (an average of four different images of the same identity). Adults showed comparable ensemble coding for all three categories (i.e., reported that matching averages had been present more than non-matching averages), providing evidence that this early stage of face learning is not shaped by face-specific experience.

Reduced Attentional Control in Older Adults Leads to Deficits in Flexible Prioritization of Visual Working Memory.

Visual working memory (VWM) resources have been shown to be flexibly distributed according to item priority. This flexible allocation of resources may depend on attentional control, an executive function known to decline with age. In this study, we sought to determine how age differences in attentional control affect VWM performance when attention is flexibly allocated amongst targets of varying priority. Participants performed a delayed-recall task wherein item priority was varied. Error was modelled using a three-component mixture model to probe different aspects of performance (precision, guess-rate, and non-target errors). The flexible resource model offered a good fit to the data from both age groups, but older adults showed consistently lower precision and higher guess rates. Importantly, when demands on flexible resource allocation were highest, older adults showed more non-target errors, often swapping in the item that had a higher priority at encoding. Taken together, these results suggest that the ability to flexibly allocate attention in VWM is largely maintained with age, but older adults are less precise overall and sometimes swap in salient, but no longer relevant, items possibly due to their lessened ability to inhibit previously attended information.

The actin cytoskeletal network plays a role in yeast prion transmission and contributes to prion stability.

Chaperone networks are required for the shearing and generation of transmissible propagons from pre-existing prion aggregates. However, other cellular networks needed for maintaining yeast prions are largely uncharacterized. Here, we establish a novel role for actin networks in prion maintenance. The [PIN+ ] prion, also known as [RNQ+ ], exists as stable variants dependent upon the chaperone machinery for the transmission of propagons to daughter cells during cell division and cytoplasmic transfer. Loss of the Hsp104 molecular chaperone leads to the growth of prion particles until they are too large to be transmitted. Here, we isolated a unique [PIN+ ] variant, which is unstable in actin mutants. This prion loss is observed over many generations, and coincides with the detection of both high molecular weight species of Rnq1 and large visible aggregates that are asymmetrically retained during cell division. Our data suggest that the irregular actin networks found in these mutants may influence propagon number by slowly permitting aggregate growth over time, resulting in the generation of nontransmissible large aggregates. Thus, we show the potential contribution of cytoskeletal networks in the transmission of prion propagons, which parallels models that have been proposed for cell-to-cell transmission of small amyloids in neurodegenerative protein aggregation diseases.

Getting to know you: The development of mechanisms underlying face learning.

Nearly every study investigating the development of face recognition has focused on the ability to tell people apart using one or two tightly controlled images to represent each identity. Such research ignores the challenge of recognizing the same person despite variability in appearance. Whereas natural variation in appearance makes unfamiliar faces difficult to recognize, by 6 years of age people easily recognize multiple images of familiar faces. Two mechanisms are proposed to underlie the process by which adults become familiar with newly encountered faces. We provide the first examination of the development of these mechanisms during childhood (6-11 years). In Experiment 1, we examined children's (6- to 10-year-olds') and adults' ability to engage in ensemble coding-the ability to rapidly extract an average representation of an identity from several instances. In Experiment 2, we examined children's ability to use within-person variability in appearance to recognize novel instances of a newly encountered identity. We created a child-friendly perceptual matching task, and the number of images to which participants were exposed varied across targets. Although children were less accurate than adults overall in Experiment 2, we found no age-related improvement in either ensemble coding or the ability to benefit from exposure to within-person variability in appearance when learning a new face, suggesting that both abilities are developed by 6 years of age. We discuss the implications of these findings for understanding the nature of mechanisms underlying face learning and other developmental processes such as language and music.