Rodent age-related impairments in discriminating perceptually similar objects parallel those observed in humans.

The ability to accurately remember distinct episodes is supported by high-level sensory discrimination. Performance on mnemonic similarity tasks, which test high-level discrimination, declines with advancing age in humans and these deficits have been linked to altered activity in hippocampal CA3 and dentate gyrus. Lesion studies in animal models, however, point to the perirhinal cortex as a brain region critical for sensory discriminations that serve memory. Reconciliation of the contributions of different regions within the cortical-hippocampal circuit requires the development of a discrimination paradigm comparable to the human mnemonic similarity task that can be used in rodents. In the present experiments, young and aged rats were cross-characterized on a spatial water maze task and two variants of an object discrimination task: one in which rats incrementally learned which object of a pair was rewarded and different pairs varied in their similarity (Experiment 1), and a second in which rats were tested on their ability to discriminate a learned target object from multiple lure objects with an increasing degree of feature overlap (Experiment 2). In Experiment 1, aged rats required more training than young to correctly discriminate between similar objects. Comparably, in Experiment 2, aged rats were impaired in discriminating a target object from lures when the pair shared more features. Discrimination deficits across experiments were correlated within individual aged rats, though, for the cohort tested, aged rats were not impaired overall in spatial learning and memory. This could suggest discrimination deficits emerging with age precede declines in spatial or episodic memory, an observation that has been made in humans. Findings of robust impairments in object discrimination abilities in the aged rats parallel results from human studies, supporting use of the developed tasks for mechanistic investigation of cortical-hippocampal circuit dysfunction in aging and disease.

Crisis-related stimuli do not increase the emotional attentional blink in a general university student population.

Crises such as natural disasters or pandemics negatively impact the mental health of the affected community, increasing rates of depression, anxiety, or stress. It has been proposed that this stems in part from crisis-related stimuli triggering negative reactions that interrupt daily life. Given the frequency and prominence of crisis events, it is crucial to understand when crisis-related stimuli involuntarily capture attention and trigger increased stress and distraction from obligations. The emotional attentional blink (EAB) paradigm-in which emotional distractors hinder report of subsequent targets in streams of rapidly displayed stimuli-allows examination of such attentional capture in a rapidly changing dynamic environment. EABs are typically observed with generally disturbing stimuli, but stimuli related to personal traumas yield similar or greater effects, indicating strong attentional capture by stimuli related to individual trauma history. The current study investigated whether a similar comparable or increased crisis-related EAB exists within a community affected by large-scale crisis. Specifically, effects of conventional emotional distractors and distractors related to recent crises were compared using EABs in university students without a mental health diagnosis. Experiment 1 used images related to Hurricane Harvey, evaluating a crisis 4 years prior to data collection. Experiment 2 used words related to the COVID pandemic, evaluating an ongoing crisis at the time of data collection. In both experiments, the conventional EAB distractors yielded strong EABs, while the crisis-related distractors yielded absent or weak EABs in the same participants. This suggests that crisis-related stimuli do not have special potency for capturing attention in the general university student population. More generally, crises affecting communities do not necessarily yield widespread, strong reactivity to crisis-related stimuli.

The slow rate of working memory consolidation from vision is a structural limit.

The speed with which information from vision is transformed into working memory (WM) representations that resist interference from ongoing perception and cognition is the subject of conflicting results. Using distinct paradigms, researchers have arrived at estimates of the consolidation time course ranging from 25 ms to 1 s - a range of more than an order of magnitude. However, comparisons of consolidation duration across very different estimation paradigms rely on the implicit assumption that WM consolidation speed is a stable, structural constraint of the WM system. The extremely large variation in WM consolidation speed estimates across measurement approaches motivated the current work's goal of determining whether consolidation speed truly is a stable structural constraint of WM encoding, or instead might be under strategic control as suggested by some accounts. By manipulating the relative task priority of WM encoding and a subsequent sensorimotor decision in a dual-task paradigm, the current experiments demonstrate that the long duration of WM consolidation does not change as a result of task-specific strategies. These results allow comparison of WM consolidation across estimation approaches, are consistent with recent multi-phase WM consolidation models, and are consistent with consolidation duration being an inflexible structural limit.

More than a feeling: The emotional attentional blink relies on non-emotional "pop out," but is weak compared to the attentional blink.

The attentional blink (AB) reveals temporal limits of goal-driven attention: the second of two proximate targets presented in a rapid stream of non-targets is often missed. In the emotional AB (EAB, also termed emotion-induced blindness), an emotionally valenced distractor replacing the first target yields a similar blink. However, the AB and EAB have not been adequately compared, and thus the extent of their mechanistic similarity remains unclear. The current study interleaved AB and EAB trials using identical stimuli in the same participants and observed that the AB is consistently larger than the EAB. Moreover, the four main experiments varied in both target-defining features (semantic vs. perceptual) and EAB distractor salience (emotion alone vs. emotion plus physical distinctiveness); an EAB was observed only when distractors were physically distinct. Even when a large EAB was observed, the AB was still larger using a task with identical targets and fillers in the same individuals. These results suggest that: (1) goal-driven attentional control (measured by the AB) has a greater influence than stimulus-driven attentional control (measured by the EAB: emotion valence and physical distinctiveness) on selection from a dynamic series of stimuli, and (2) emotional valence is insufficient on its own to trigger an EAB. However, these results are consistent with the account that when attention has already been captured by a physically salient distractor, emotional content can interfere with disengagement from the already-attended stimulus.

Nontarget emotional stimuli must be highly conspicuous to modulate the attentional blink.

The attentional blink (AB) is often considered a top-down phenomenon because it is triggered by matching an initial target (T1) in a rapid serial visual presentation (RSVP) stream to a search template. However, the AB is modulated when targets are emotional, and is evoked when a task-irrelevant, emotional critical distractor (CDI) replaces T1. Neither manipulation fully captures the interplay between bottom-up and top-down attention in the AB: Valenced targets intrinsically conflate top-down and bottom-up attention. The CDI approach cannot manipulate second target (T2) valence, which is critical because valenced T2s can "break through" the AB (in the target-manipulation approach). The present research resolves this methodological challenge by indirectly measuring whether a purely bottom-up CDI can modulate report of a subsequent T2. This novel approach adds a valenced CDI to the "classic," two-target AB. Participants viewed RSVP streams containing a T1-CDI pair preceding a variable lag to T2. If the CDI's valence is sufficient to survive the AB, it should modulate T2 performance, indirectly signaling bottom-up capture by an emotional stimulus. Contrary to this prediction, CDI valence only affected the AB when CDIs were also extremely visually conspicuous. Thus, emotional valence alone is insufficient to modulate the AB.

Reevaluating the sensory recruitment model by manipulating crowding in visual working memory representations.

The prominent sensory recruitment model argues that visual working memory (WM) is maintained via representations in the same early visual cortex brain regions that initially encode sensory stimuli, either in the identical neural populations as perceptual representations or in distinct neural populations. While recent research seems to reject the former (strong) sensory recruitment model, the latter (flexible) account remains plausible. Moreover, this flexibility could explain a recent result of high theoretical impact (Harrison & Bays, The Journal of Neuroscience, 38 (12), 3116-3123, 2018) - a failure to observe interactions between items held in visual WM - that has been taken to reject the sensory recruitment model. Harrison and Bays (The Journal of Neuroscience, 38 (12), 3116-3123, 2018) tested the sensory recruitment model by comparing the precision of memoranda in radially and tangentially oriented memory arrays. Because perceptual visual crowding effects are greater in radial than tangential arrays, they reasoned that a failure to observe such anisotropy in WM would reject the sensory recruitment model. In the present Registered Report or Replication, we replicated their study with greater sensitivity and extended their task by controlling a potential strategic confound. Specifically, participants might remap memory items to new locations, reducing interactions between proximal memoranda. To combat remapping, we cued participants to report either a memory item or its precise location - with this report cue presented only after a memory maintenance period. Our results suggest that, similar to visual perceptual crowding, location-bound visual memoranda interact with one another when remapping is prevented. Thus, our results support at least a flexible form of the sensory recruitment model.