Impaired Memory Awareness and Loss Integration in Self-Referential Network Across the Progression of Alzheimer’s Disease Spectrum

Background: Anosognosia, or unawareness of memory deficits, is a common manifestation of Alzheimer’s disease (AD), but greatly variable in subjective cognitive decline (SCD) and amnestic mild cognitive impairment (aMCI) subjects. Self-referential network (SRN) is responsible for self-referential processing and considered to be related to AD progression. Objective: Our aim is to explore connectivity changes of SRN and its interaction with memory-related network and primary sensorimotor network (SMN) in the AD spectrum. Methods: About 444 Alzheimer’s Disease Neuroimaging Initiative subjects (86 cognitively normal [CN]; 156 SCD; 146 aMCI; 56 AD) were enrolled in our study. The independent component analysis (ICA) method was used to extract the SRN, SMN, and memory-related network from all subjects. The alteration of functional connectivity (FC) within SRN and its connectivity with memory-related network/SMN were compared among four groups and further correlation analysis between altered FC and awareness index as well as episodic memory score were performed. Results: Compared with CN group, individuals with SCD exhibited hyperconnectivity within SRN, while aMCI and AD patients showed hypoconnectivity. Furthermore, aMCI patients and AD patients both showed the interruption of the FC between the SRN and memory-related network compared to CN group. Pearson correlation analysis showed that disruptive FC within SRN and its interaction with memory-related network were related to memory awareness and episodic memory scores. Conclusion: In conclusion, impaired memory awareness and episodic memory in the AD spectrum are correlated to the disconnection within SRN and its interaction with memory-related network.

Self-awareness for Financial Decision Making Abilities Is Linked to Right Temporal Cortical Thickness in Older Adults

Everyday financial decision making and the awareness of the integrity of one’s financial decision making abilities (or financial awareness) are both critical to study in older adults as they can help identify those at risk for making suboptimal financial decisions and prevent financial loss. In the current study, we examined the cognitive and cortical thickness correlates of financial decision making and financial awareness in 59 community-dwelling participants co-enrolled in a larger study (mean age=68.35 years (SD=5.5), mean education=15.91 (SD=2.36), 61% = women, 67% = White). Data from standardized measures of financial decision making and cognition was investigated along with FreeSurfer derived thickness regions. Based on metacognitive frameworks, financial awareness was measured along with a well-validated measure of memory awareness. Results revealed that numeracy, executive functioning and vocabulary were associated with financial decision making, whereas in analysis adjusted for financial decision making, memory awareness relative to cognition was most strongly linked to financial awareness. No significant associations between thickness and financial decision making were found. However, both financial and memory awareness were associated with the same right-hemisphere temporal thickness regions underscoring the idea of a common substrate of awareness. Interestingly, our findings converge with the emerging work on financial exploitation in which the right sided temporal regions have been found to play a prominent role. Incorporating the contributing role of self-awareness in various models of financial exploitation will be an important consideration for future studies.

Subjective cognitive decline: opposite links to neurodegeneration across the Alzheimer’s continuum

Subjective memory decline is associated with neurodegeneration and increased risk of cognitive decline in participants with no or subjective cognitive impairment, while in patients with mild cognitive impairment or Alzheimer’s-type dementia, findings are inconsistent. Our aim was to provide a comprehensive overview of subjective memory decline changes, relative to objective memory performances, and of their relationships with neurodegeneration, across the clinical continuum of Alzheimer’s disease. Two hundred participants from the Imagerie Multimodale de la maladie d'Alzheimer à un stade Précoce (IMAP+) primary cohort and 731 participants from the Alzheimer’s Disease Neuroimaging Initiative (ADNI) replication cohort were included. They were divided into four clinical groups (Imagerie Multimodale de la maladie d'Alzheimer à un stade Précoce/Alzheimer’s Disease Neuroimaging Initiative): controls (n = 67/147, age: 60–84/60–90, female: 54/55%), patients with subjective cognitive decline (n = 30/84, age: 54–84/65–80, female: 44/63%), mild cognitive impairment (n = 50/369, age: 58–86/55–88, female: 45/44%) or Alzheimer’s-type dementia (n = 36/121, age: 51–86/61–90, female: 41/41%). Subjective and objective memory scores, and their difference (i.e. delta score reflecting memory awareness), were compared between groups. Then, voxelwise relationships between subjective memory decline and neuroimaging measures of neurodegeneration [atrophy (T1-MRI) and hypometabolism (18F-fluorodeoxyglucose-PET)] were assessed across clinical groups and the interactive effect of the level of cognitive impairment within the entire sample was assessed. Analyses were adjusted for age, sex and education, and repeated including only the amyloid-positive participants. In Imagerie Multimodale de la maladie d'Alzheimer à un stade Précoce, the level of subjective memory decline was higher in all patient groups (all P < 0.001) relative to controls, but similar between patient groups. In contrast, objective memory deficits progressively worsened from the subjective cognitive decline to the dementia group (all P < 0.001). Accordingly, the delta score showed a progressive decline in memory awareness across clinical groups (all P < 0.001). Voxelwise analyses revealed opposite relationships between the subjective memory decline score and neurodegeneration across the clinical continuum. In the earliest stages (i.e. patients with subjective cognitive decline or Mini Mental State Examination > 28), greater subjective memory decline was associated with increased neurodegeneration, while in later stages (i.e. patients with mild cognitive impairment, dementia or Mini Mental State Examination < 27) a lower score was related to more neurodegeneration. Similar findings were recovered in the Alzheimer’s Disease Neuroimaging Initiative replication cohort, with slight differences according to the clinical group, and in the amyloid-positive subsamples. Altogether, our findings suggest that the subjective memory decline score should be interpreted differently from normal cognition to dementia. Higher scores might reflect greater neurodegeneration in earliest stages, while in more advanced stages lower scores might reflect decreased memory awareness, i.e. more anosognosia associated with advanced neurodegeneration.

Conscious and unconscious memory differentially impact attention: Eye movements, visual search, and recognition processes

A hotly debated question is whether memory influences attention through conscious or unconscious processes. To address this controversy, we measured eye movements while participants searched repeated real-world scenes for embedded targets, and we assessed memory for each scene using confidence-based methods to isolate different states of subjective memory awareness. We found that memory-informed eye movements during visual search were predicted both by conscious recollection, which led to a highly precise first eye movement toward the remembered location, and by unconscious memory, which increased search efficiency by gradually directing the eyes toward the target throughout the search trial. In contrast, these eye movement measures were not influenced by familiarity-based memory (i.e., changes in subjective reports of memory strength). The results indicate that conscious recollection and unconscious memory can each play distinct and complementary roles in guiding attention to facilitate efficient extraction of visual information.

The Influence of Memory-Aware Computation on Distributed BLAST

Background: One of the pivotal challenges in nowadays genomic research domain is the fast processing of voluminous data such as the ones engendered by high-throughput Next-Generation Sequencing technologies. On the other hand, BLAST (Basic Local Alignment Search Tool), a longestablished and renowned tool in Bioinformatics, has shown to be incredibly slow in this regard. Objective: To improve the performance of BLAST in the processing of voluminous data, we have applied a novel memory-aware technique to BLAST for faster parallel processing of voluminous data. Method: We have used a master-worker model for the processing of voluminous data alongside a memory-aware technique in which the master partitions the whole data in equal chunks, one chunk for each worker, and consequently each worker further splits and formats its allocated data chunk according to the size of its memory. Each worker searches every split data one-by-one through a list of queries. Results: We have chosen a list of queries with different lengths to run insensitive searches in a huge database called UniProtKB/TrEMBL. Our experiments show 20 percent improvement in performance when workers used our proposed memory-aware technique compared to when they were not memory aware. Comparatively, experiments show even higher performance improvement, approximately 50 percent, when we applied our memory-aware technique to mpiBLAST. Conclusion: We have shown that memory-awareness in formatting bulky database, when running BLAST, can improve performance significantly, while preventing unexpected crashes in low-memory environments. Even though distributed computing attempts to mitigate search time by partitioning and distributing database portions, our memory-aware technique alleviates negative effects of page-faults on performance.

Memory Awareness (Kesadaran Memori) pada Anak

Memory awareness (kesadaran memori) adalah salah satu bagian dari metakognitif. Anak-anak memiliki kemampuan untuk memantau performance memori diri sendiri (metacognitive monitoring). Penelitian observasi partisipan pada anak usia 4-11 tahun ini bertujuan untuk melihat ketepatan memory awareness (kesadaran memori) mereka serta memeriksa pemahaman anak-anak tersebut akan proses memorinya. Hasil observasi menunjukkan (t = - 4.239, p = 0.001) bahwa partisipan (anak usia 4-11 tahun) mengalami peningkatan signifikan antara jumlah gambar yang mungkin diingat (prediksi penilaian keyakinan) dan performance aktual. Anak-anak usia yang lebih muda optimis mengenai kemampuan mengingat dibandingkan usia di atasnya