Memory perfectionism is associated with persistent memory complaints after concussion

Objective: The etiology of persistent memory complaints after concussion is poorly understood. Memory perfectionism (highly valuing memory ability and intolerance of minor memory lapses) may help explain why some people report persistent subjective memory problems in the absence of corresponding objective memory impairment. The present study investigated the relationship between memory perfectionism and persistent memory complaints after concussion. Methods: Adults (N=77; 61% women) with persistent symptoms following concussion were recruited from outpatient specialty clinics. Participants completed the National Institutes of Health Toolbox Cognition Battery, Test of Memory Malingering-Trial 1, and questionnaires measuring memory perfectionism (Memory in Adulthood-Achievement subscale), forgetfulness and other post-concussion symptoms (Rivermead Postconcussion Symptoms Questionnaire; RPQ), and depression (Patient Health Questionnaire-2) at M=17.8 weeks post-injury. Patients with vs. without severe memory complaints (based on the RPQ) were compared. Results: Memory perfectionism was associated with severe memory complaint, after controlling for objective memory ability, overall cognitive ability, and depression (95% confidence interval for odds ratio = 1.11 to 1.40). Sensitivity analyses showed that this relationship did not depend on use of specific objective memory tests nor on inclusion of participants who failed performance validity testing. In a control comparison to test the specificity of identified relationships, memory perfectionism was not associated with severe fatigue (95% confidence interval for odds ratio = 0.91 to 1.07). Discussion: Memory perfectionism may predispose people to experience persistent memory symptoms and/or contribute to their perpetuation after concussion, with potential relevance to the spectrum of functional cognitive disorders more broadly.

Drifting assemblies for persistent memory: Neuron transitions and unsupervised compensation

Change is ubiquitous in living beings. In particular, the connectome and neural representations can change. Nevertheless, behaviors and memories often persist over long times. In a standard model, associative memories are represented by assemblies of strongly interconnected neurons. For faithful storage these assemblies are assumed to consist of the same neurons over time. Here we propose a contrasting memory model with complete temporal remodeling of assemblies, based on experimentally observed changes of synapses and neural representations. The assemblies drift freely as noisy autonomous network activity and spontaneous synaptic turnover induce neuron exchange. The gradual exchange allows activity-dependent and homeostatic plasticity to conserve the representational structure and keep inputs, outputs, and assemblies consistent. This leads to persistent memory. Our findings explain recent experimental results on temporal evolution of fear memory representations and suggest that memory systems need to be understood in their completeness as individual parts may constantly change.

Two Birds With One Stone: Boosting Both Search and Write Performance for Tree Indices on Persistent Memory

The advance of byte-addressable persistent memory (PM) makes it a hot topic to revisit traditional tree indices such as B+-tree and radix tree, and a few new persistent memory-friendly tree indices have been proposed. However, due to the special features of persistent memory compared to DRAM and the limitations of B+-tree-like indices, it is much harder to optimize both search and write performance for tree indices on persistent memory. As a result, most existing indices for persistent memory, e.g., WB-tree, proposed to improve write performance while sacrificing search performance. Aiming to optimize both write and search performance for tree indices on persistent memory, in this paper, we first propose a novel Two-Layer Architecture (TLA) for constructing tree indices on persistent memory. The key idea, of TLA is to organize the index with a search-optimized top layer and a write-optimized bottom layer, letting the top layer optimize search performance and the bottom layer improve write performance. By adopting efficient structures for the two layers, TLA can boost both write and search performance for tree indices on persistent memory. Following the TLA architecture, we present a new index called TLBtree (Two-Layer B+-tree) offering high search and write performance for persistent memory. Moreover, we develop a concurrent TLBtree to support non-blocking read operations in multi-core environment. We evaluate our proposals under a server equipped with real Intel Optane persistent memory. The results show that TLBtree outperforms the state-of-the-art tree indices, including WB-tree, Fast&Fair, and FPTree, in both search and write performance. Also, the concurrent TLBtree can achieve up to 3.7x speedup than its competitors under the multi-core environment.

Developmental emergence of persistent memory for contextual and auditory fear in mice

The ability to generate memories that persist throughout a lifetime (that is, memory persistence) emerges in early development across species. Although it has been shown that persistent fear memories emerge between late infancy and adolescence in mice, it is unclear exactly when this transition takes place, and whether two major fear conditioning tasks, contextual and auditory fear, share the same time line of developmental onset. Here, we compared the ontogeny of remote contextual and auditory fear in C57BL/6J mice across early life. Mice at postnatal day (P)15, 21, 25, 28, and 30 underwent either contextual or auditory fear training and were tested for fear retrieval 1 or 30 d later. We found that mice displayed 30-d memory for context– and tone–fear starting at P25. We did not find sex differences in the ontogeny of either type of fear memory. Furthermore, 30-d contextual fear retrieval led to an increase in the number of c-Fos positive cells in the prelimbic region of the prefrontal cortex only at an age in which the contextual fear memory was successfully retrieved. These data delineate a precise time line for the emergence of persistent contextual and auditory fear memories in mice and suggest that the prelimbic cortex is only recruited for remote memory recall upon the onset of memory persistence.