Memory as a scale of simulation depending on the trace distinctiveness.

It has been proposed that representations emerge from a single memory system organized along a continuum of specificity. This continuum is assumed to reflect a scale between the simulation of overlapping and specific features of the traces, which depends on trace distinctiveness. More specifically, higher trace distinctiveness facilitates the simulation of trace-specific features, which increase the discriminability of traces and lead to the emergence of a more specific representation. In two experiments, participants were asked to identify match (low task discrimination demand) or mismatch (high task discrimination demand) associations between actions and characters that were visually either highly or lowly distinctive. The results of Experiment 1 show that in the high-distinctiveness context, performance was better when identifying a mismatch rather than a match, while the opposite was true in the low-distinctiveness context. The results of Experiment 2 show that using a dynamic visual noise to interfere with the participants' ability to simulate the features of the characters also reduced the benefit of the high-distinctiveness context for the mismatch trials (Experiment 2a and 2b) and increased the benefit of the low-distinctiveness context for the match trials (Experiment 2b). Taken together, these results suggest that the simulation of trace-specific features underlies the emergence of specific representations, which can be beneficial when the discrimination demand of the task is high and detrimental when this demand is low. Memory might therefore be viewed as a scale of simulation between overlapping and specific trace features.

Does an increase in physiological indexes predict better cognitive performance: the PhyCog randomised cross-over protocol in type 2 diabetes.

INTRODUCTION: There has been a growing interest towards cognitive-training programmes to improve cognition and prevent cognitive impairment despite discrepant findings. Physical activity has been recognised in maintaining or improving cognitive ability. Based on a psychoneurophysiological approach, physiological indexes should partly determine neuronal dynamics and influence cognition as any effects of cognitive training. This study's primary aim was to examine if improved physiological indexes predict improved cognitive variables in the context of a clinical intervention programme for type 2 diabetes (T2D). METHOD AND ANALYSIS: PhyCog will be a 22-week randomised controlled trial comparing cognitive performance between three arms: (1) physical activity (1 month), a 15-day wash-out, then cognitive training (1 month), (2) cognitive training (1 month), a 15-day wash-out and physical activity (1 month), and (3) an active breathing condition (psychoeducation and resonance frequency breathing for 1 month), then a 15-day wash-out, and combined physical activity and cognitive training (1 month), allowing to determine the most effective intervention to prevent cognitive impairment associated with T2D. All participants will be observed for 3 months following the intervention. The study will include a total of 81 patients with T2D.Cognitive performance and physiological variables will be assessed at baseline (week 0-W0), during the washout (W5, 72-96 hours after week 4), at the end of the intervention (W10), and at the end of the follow-up (W22). The main variables of interest will be executive function, memory and attention. Physiological testing will involve allostatic load such as heart rate variability, microcirculation, cortisol and dehydroepiandrosterone sulfate levels. Sociodemographic and body composition will also be a consideration. Assessors will all be blinded to outcomes. To test the primary hypothesis, the relationship between improvement in physiological variables and improvement in cognitive variables (executive, memory and attention) will be collected. ETHICS AND DISSEMINATION: This protocol was approved by the Est III French Ethics Committee (2020-A03228-31). Results will be published in peer-reviewed journals. TRIAL REGISTRATION NUMBER: NCT04915339.

When does vagal activity benefit to the discrimination of highly overlapping memory traces?

Distinguishing among similar events is indeed crucial to memory. In a dangerous context, this ability may be less essential, whereas in a secure context it may provide an adaptative advantage notably in social situations. Vagal activity as a marker of the individual's adaptation in social engagement contexts might predict the ability to discriminate highly similar memories in an unthreatening context. The present study aims to test the relation between vagal activity and memory discrimination by manipulating the visual distinctiveness of stimuli (high vs. low) in an ecological memory discrimination task with humanoid characters. It was expected that vagal activity support adaptive self-regulatory processes which may be needed only when the memory discrimination is challenging (low distinctiveness between true memory and lure). In a study phase, multiple realistic fictional humanoid characters performed the same action on different objects. The characters could be very similar or very distinct one to each other. Then, during a test phase, the participants had to discriminate whether a displayed character on the screen was exactly matched the one performing the given action on a specific object in the study phase (target). Vagal activity was assessed in undergraduate students (n = 40) before the study phase. Higher vagal activity predicted better memory discrimination performance specifically when the distinctiveness between the lure and target was low. These data extend previous work on vagal activity and memory suggesting that heart-brain interactions represent an adaptive psychophysiological mechanism underlying memory discrimination specifically when it is challenging in an unthreatening context.

Playing "guess who?": when an episodic specificity induction increases trace distinctiveness and reduces memory errors during event reconstruction.

The constructive nature of memory implies a possible confusion between details of similar events. Memory interventions should thus target the reduction of memory errors. We postulate that a brief intervention called Episodic Specificity Induction (ESI) facilitates the sensorimotor simulation of event-related details by improving the distinctiveness of the event memory trace. As such, ESI should reduce memory errors only when event memory traces are strongly overlapping based on their sensorimotor features. Participants memorised videos showing characters performing an action on a given object. The characters were either visually very similar to each other or very distinct (low vs. high distinctiveness condition). Next, participants performed either an imagination version of the ESI or a control induction. Finally, a voice announced one of the actions seen and a character was then briefly displayed. The participants had to indicate whether the association was correct. For incorrect associations, in the low distinctiveness condition, false alarms were more likely than in the high distinctiveness condition and were reduced after the ESI. It suggests that facilitating the simulation of specific details through the ESI increased trace distinctiveness and reduced memory errors at the critical time of event reconstruction. Future clinical applications might be possible.

Low-Resolution Neurocognitive Aging and Cognition: An Embodied Perspective.

Consistent with embodied cognition, a growing evidence in young adults show that sensorimotor processing is at the core of cognition. Considering that this approach predicts direct interaction between sensorimotor processing and cognition, embodied cognition may thus be particularly relevant to study aging, since this population is characterized by concomitant changes in sensorimotor and cognitive processing. The present perspective aims at showing the value and interest to explore normal aging throughout embodiment by focusing on the neurophysiological and cognitive changes occurring in aging. To this end, we report some of the neurophysiological substrates underpinning the perceptual and memory interactions in older adults, from the low and high perceptual processing to the conjunction in the medial temporal lobe. We then explore how these changes could explain more broadly the cognitive changes associated with aging in terms of losses and gains.