Dynamic patterns of functional connectivity in the human brain underlie individual memory formation.

Remembering our everyday experiences involves dynamically coordinating information distributed across different brain regions. Investigating how momentary fluctuations in connectivity in the brain are relevant for episodic memory formation, however, has been challenging. Here we leverage the high temporal precision of intracranial EEG to examine sub-second changes in functional connectivity in the human brain as 20 participants perform a paired associates verbal memory task. We first identify potential functional connections by selecting electrode pairs across the neocortex that exhibit strong correlations with a consistent time delay across random recording segments. We then find that successful memory formation during the task involves dynamic sub-second changes in functional connectivity that are specific to each word pair. These patterns of dynamic changes are reinstated when participants successfully retrieve the word pairs from memory. Therefore, our data provide direct evidence that specific patterns of dynamic changes in human brain connectivity are associated with successful memory formation.

Neuronal sequences in population bursts encode information in human cortex.

Neural coding has traditionally been examined through changes in firing rates and latencies in response to different stimuli1-5. However, populations of neurons can also exhibit transient bursts of spiking activity, wherein neurons fire in a specific temporal order or sequence6-8. The human brain may utilize these neuronal sequences within population bursts to efficiently represent information9-12, thereby complementing the well-known neural code based on spike rate or latency. Here we examined this possibility by recording the spiking activity of populations of single units in the human anterior temporal lobe as eight participants performed a visual categorization task. We find that population spiking activity organizes into bursts during the task. The temporal order of spiking across the activated units within each burst varies across stimulus categories, creating unique stereotypical sequences for individual categories as well as for individual exemplars within a category. The information conveyed by the temporal order of spiking activity is separable from and complements the information conveyed by the units' spike rates or latencies following stimulus onset. Collectively, our data provide evidence that the human brain contains a complementary code based on the neuronal sequence within bursts of population spiking to represent information.

Discrimination of mnemonic similarity is associated with short-term and long-term memory precision.

Remembering specific memories with precision relies on the differentiation of similar memory contents - a process commonly referred to as pattern separation and behaviorally operationalized as lure discrimination in the mnemonic similarity task. Although pattern separation is typically investigated in the context of long-term memory (LTM), recent research extends these findings to short-term memory (STM) within a mixture model framework, emphasizing the distinction between memory quality and quantity. According to this framework, pattern separation is associated with memory precision across STM and LTM, regardless of the overall memory likelihood. However, these associations among memory quality measures may persist without the mixture model assumption. In an alternative model, a unitary memory strength measure quantified as a discrimination score (d') may also capture the association between pattern separation and memory quality, as pattern separation has been previously linked with strength-based memory performance. We tested these possibilities based on individual differences among 132 participants who underwent tasks measuring mnemonic pattern separation and STM/LTM quality. We found that behavioral estimates of pattern separation are significantly correlated with STM and LTM precision, irrespective of the likelihood of STM/LTM recall success. However, these associations are absent when considering the correlation between pattern separation and memory strength under a unitary model framework. By leveraging individual differences to constrain our understanding of cognitive models, our data unravel the intricate relationship between pattern separation and memory quality across timescales. These findings may therefore contribute to identifying sensitive behavioral measures for detecting subtle memory deficits in older adults or clinical populations.

Inhibition of ADAM17 attenuates high glucose-induced angiogenesis and inflammation in endothelial cells partly through down-regulation of GRO-α/CXCR2 expression: implications in peritoneal dialysis.

BACKGROUND: Angiogenesis and inflammation are key events leading to peritoneal morphologic alteration and ultrafiltration failure in patients undergoing peritoneal dialysis (PD). The current study aims to explore the role of ADAM17 in the angiogenetic and inflammatory responses of endothelial cells. METHODS: Human umbilical vein endothelial cells (HUVECs) were cultured and treated with a high glucose-containing medium. In parallel experiments, the expression of ADAM17 in HUVECs was inhibited by SiRNA interference. The mRNA and protein expression of ADAM17, GRO-α and CXCR2 were assessed by qPCR and Western blotting, respectively. The concentrations of GRO-α, VEGF, IL-6 and TNF-α in the cellular supernatants were determined by ELISA. Tube formation and migration of HUVECs were evaluated by Matrigel and transwell migration apparatus. RESULTS: High glucose increased the expression of ADAM17, CXCR2 and GRO-α in cultured HUVECs. RNA silencing of ADAM17 abolished high glucose-mediated increase of GRO-α and CXCR2, which were accompanied by reduced secretion of VEGF, IL-6, TNF-α, as well as tube formation and cell migration in HUVECs. CONCLUSIONS: Inhibition of ADAM17 ameliorates high glucose-induced angiogenic and inflammatory responses in endothelial cells partly through down-regulation of GRO-α/CXCR2 expression.

Focal seizures induce spatiotemporally organized spiking activity in the human cortex.

Epileptic seizures are debilitating because of the clinical symptoms they produce. These symptoms, in turn, may stem directly from disruptions in neural coding. Recent evidence has suggested that the specific temporal order, or sequence, of spiking across a population of cortical neurons may encode information. Here, we investigate how seizures disrupt neuronal spiking sequences in the human brain by recording multi-unit activity from the cerebral cortex in five male participants undergoing monitoring for seizures. We find that pathological discharges during seizures are associated with bursts of spiking activity across a population of cortical neurons. These bursts are organized into highly consistent and stereotyped temporal sequences. As the seizure evolves, spiking sequences diverge from the sequences observed at baseline and become more spatially organized. The direction of this spatial organization matches the direction of the ictal discharges, which spread over the cortex as traveling waves. Our data therefore suggest that seizures can entrain cortical spiking sequences by changing the spatial organization of neuronal firing, providing a possible mechanism by which seizures create symptoms.

Perceptual encoding benefit of visual memorability on visual memory formation.

Human observers often exhibit remarkable consistency in remembering specific visual details, such as certain face images. This phenomenon is commonly attributed to visual memorability, a collection of stimulus attributes that enhance the long-term retention of visual information. However, the exact contributions of visual memorability to visual memory formation remain elusive as these effects could emerge anywhere from early perceptual encoding to post-perceptual memory consolidation processes. To clarify this, we tested three key predictions from the hypothesis that visual memorability facilitates early perceptual encoding that supports the formation of visual short-term memory (VSTM) and the retention of visual long-term memory (VLTM). First, we examined whether memorability benefits in VSTM encoding manifest early, even within the constraints of a brief stimulus presentation (100-200 ms; Experiment 1). We achieved this by manipulating stimulus presentation duration in a VSTM change detection task using face images with high- or low-memorability while ensuring they were equally familiar to the participants. Second, we assessed whether this early memorability benefit increases the likelihood of VSTM retention, even with post-stimulus masking designed to interrupt post-perceptual VSTM consolidation processes (Experiment 2). Last, we investigated the durability of memorability benefits by manipulating memory retention intervals from seconds to 24 h (Experiment 3). Across experiments, our data suggest that visual memorability has an early impact on VSTM formation, persisting across variable retention intervals and predicting subsequent VLTM overnight. Combined, these findings highlight that visual memorability enhances visual memory within 100-200 ms following stimulus onset, resulting in robust memory traces resistant to post-perceptual interruption and long-term forgetting.

Sarcopenia predicts cardiovascular disease in chronic kidney disease at advanced stage and associated risks.

Chronic kidney disease (CKD) has been associated with a higher risk of cardiovascular disease (CVD), and sarcopenia is a new risk factor for CKD. However, whether sarcopenia predicts CVD in CKD remains to be determined. Sarcopenia would predict CVD in CKD at advanced stage. This analysis included 101 patients with CKD at stage 3 or over to determine the prevalence of sarcopenia and cardiovascular disease in patients with CKD at stage 3 or over in our center. The patients were further categorized into sarcopenia group (N = 19) and non-sarcopenia group (N = 82) according to the diagnostic criteria for sarcopenia. Data on demographics, laboratory tests, and measurements of extracardiac adipose tissue thickness (EAT) was collected. The prevalence of sarcopenia in patients with CKD at stage ≥ 3 was 19%. Compared with non-sarcopenia group, patients from the sarcopenia group were older (P = .005), and presented longer disease durations (P = .002). The serum level of albumin was significantly decreased, (P = .047), and high-sensitivity C-reactive protein level (CRP) was significantly increased (P = .003) in sarcopenia group. In addition, the EAT was thicker in the sarcopenia group compared with non-sarcopenia group (P = .032). Furthermore, the le-stratified atherosclerotic cardiovascular disease (ASCVD) risk scores were positively correlated with inflammation, nutrition, body mass index (BMI) and disease duration of CKD in sarcopenia group (P < .001). Patients with CKD are prone to have sacropenia, which is associated with inflammation and malnutrition. Presence of sarcopenia in CKD patients predicts the risk of ASCVD.

Clinical risk factors for peritoneal dialysis withdrawal at different dialysis duration.

BACKGROUND: The duration of patients maintained on peritoneal dialysis (PD) varied. This study investigated the clinical risk factors for PD withdrawal at different dialysis duration. METHODS: Patients who initiated PD from 1994 to 2011 were recruited and followed for at least 10 years until 2021. Patients were grouped into four groups according to dialysis duration or time on treatment (TOT) when withdrew PD. RESULTS: A cohort of 586 patients were enrolled (mean age of 54.9 years, median dialysis duration or TOT of 47.9 months). Patients who maintained PD for longer than 10 years were younger, with lower prevalence of diabetes, lower serum C-reactive protein (CRP) level and white blood cell (WBC) count, higher serum albumin and pre-albumin level, higher normalized protein catabolic rate (nPCR) and residual kidney function, and more common use of renin-angiotensin system inhibitors (RASi) at baseline (p < 0.05 for all). Peritonitis related death and ultrafiltration failure related HD transferring increased along with time on PD (p < 0.001). Old age, diabetes, low serum albumin, high WBC count, hypertensive nephropathy, and nonuse of RASi were associated with increased risk of non-transplantation related PD withdrawal (p < 0.05 for all). Low baseline CRP and use of RASi were independent predictors for long-term PD maintenance (p < 0.05 for all). CONCLUSIONS: Long-term PD patients demonstrated young age, low prevalence of diabetes, better nutrition status, absence of inflammation, better residual kidney function, and higher proportion of RASi usage at baseline. Absence of inflammation and use of RASi were independently associated with long-term PD maintenance.

Detrimental effects of effortful physical exertion on a working memory dual-task in older adults.

Action and cognition often interact in everyday life and are both sensitive to the effects of aging. The present study tested the effects of a simple physical action, effortful handgrip exertion, on working memory (WM) and inhibitory control in younger and older adults. Using a novel dual-task paradigm, participants engaged in a WM task with 0 or 5-distractors under concurrent physical exertion (5% vs. 30% individual maximum voluntary contraction). Effortful physical exertion, although failing to effect WM accuracy in the distractor absent condition for both age groups, reduced WM accuracy for the older, but not young adults, in the distractor-present condition. Similarly, older adults experienced greater distractor interference in the distractor-present condition under high physical exertion, indexed by slower reaction time (RT), confirmed by hierarchical Bayesian modeling of RT distributions. Our finding that a simple but effortful physical task results in impaired cognitive control may be empirically important for understanding everyday functions of older adults. For example, the ability to ignore task-irrelevant items declines with age and this decline is greater when simultaneously performing a physical task, which is a frequent occurrence in daily life. The negative interactions between cognitive and motor tasks may further impair daily functions, beyond the negative consequences of reduced inhibitory control and physical abilities in older adults. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Effortfulness of visual working memory: Gauged by physical exertion.

Active maintenance of information in working memory (WM) is an essential but effortful cognitive process. Yet, the effortful nature of WM remains poorly understood. Here, we constructed a model to evaluate how perceived effort of WM is directly compared to that of physical exertion. In Experiment 1, participants freely chose to either remember a certain number of colors in a visual WM task or hold a hand dynamometer to a required percentage of maximal voluntary contraction (%MVC) to obtain a fixed task credit upon successful task completion. We found that participants discounted WM-related effort in the same way as they discounted handgrip-related effort based on a computation of expected choice outcomes (hence utility) associated with different task loads. This rationality in an observer's prospective choice in Experiment 1 was generalized to retrospective choice in Experiment 2 where participants reported which task was more effortful immediately after they had performed both tasks in a randomized order without any reward or feedback. Experiment 3 further probed this shared mechanism using a dual-task paradigm. As predicted by our model, we found that physical exertion could disrupt the performance in the concurrent WM task, proportional to the iso-effort relationship between WM and physical exertion when task loads were high for both tasks. Collectively, our findings converge on a shared computational principle connecting task load, perceived effort, and choice utility across physical and cognitive domains. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Pupillary evidence reveals the influence of conceptual association on brightness perception.

Our visual experience often varies based on momentary thoughts and feelings. For example, when positive concepts are invoked, visual objects may appear brighter (e.g., a "brighter" smile). However, it remains unclear whether this phenomenological experience is driven by a genuine top-down modulation of brightness perception or by a mere response bias. To investigate this issue, we use pupillometry as a more objective measure of perceived brightness. We asked participants to judge the brightness level of an iso-luminant gray color patch after evaluating the valence of a positive or negative word. We found that the gray color patch elicited greater pupillary light reflex and more frequent "brighter" responses after observers had evaluated the valence of a positive word. As pupillary light reflex is unlikely driven by voluntary control, these results suggest that the conceptual association between affect and luminance can modulate brightness perception.

The medial temporal lobe supports the quality of visual short-term memory representation.

The quality of short-term memory (STM) underlies our ability to recall the exact details of a recent event, yet how the human brain enables this core cognitive function remains poorly understood. Here we use multiple experimental approaches to test the hypothesis that the quality of STM, such as its precision or fidelity, relies on the medial temporal lobe (MTL), a region commonly associated with the ability to distinguish similar information remembered in long-term memory. First, with intracranial recordings, we find that delay-period MTL activity retains item-specific STM content that is predictive of subsequent recall precision. Second, STM recall precision is associated with an increase in the strength of intrinsic MTL-to-neocortical functional connections during a brief retention interval. Finally, perturbing the MTL through electrical stimulation or surgical removal can selectively reduce STM precision. Collectively, these findings provide converging evidence that the MTL is critically involved in the quality of STM representation.

The entorhinal-DG/CA3 pathway in the medial temporal lobe retains visual working memory of a simple surface feature.

Classic models consider working memory (WM) and long-term memory as distinct mental faculties that are supported by different neural mechanisms. Yet, there are significant parallels in the computation that both types of memory require. For instance, the representation of precise item-specific memory requires the separation of overlapping neural representations of similar information. This computation has been referred to as pattern separation, which can be mediated by the entorhinal-DG/CA3 pathway of the medial temporal lobe (MTL) in service of long-term episodic memory. However, although recent evidence has suggested that the MTL is involved in WM, the extent to which the entorhinal-DG/CA3 pathway supports precise item-specific WM has remained elusive. Here, we combine an established orientation WM task with high-resolution fMRI to test the hypothesis that the entorhinal-DG/CA3 pathway retains visual WM of a simple surface feature. Participants were retrospectively cued to retain one of the two studied orientation gratings during a brief delay period and then tried to reproduce the cued orientation as precisely as possible. By modeling the delay-period activity to reconstruct the retained WM content, we found that the anterior-lateral entorhinal cortex (aLEC) and the hippocampal DG/CA3 subfield both contain item-specific WM information that is associated with subsequent recall fidelity. Together, these results highlight the contribution of MTL circuitry to item-specific WM representation.

Negative emotion reduces visual working memory recall variability: A meta-analytical review.

Negative emotion is often hypothesized to trigger a more deliberate processing mode. This effect can manifest as increased precision of information maintained in working memory (WM) captured by reduced WM recall variability under an induced negative emotional state. However, some recent evidence shows that WM representations are immune to any emotional influences. Here, we meta-analyze existing evidence based on data from 13 experiments across 491 participants who performed a delay-estimation WM task under negative and neutral emotional states. We find that induced negative emotional state modestly reduces WM recall variability and increases recall failures relative to the neutral condition. These effects are moderated by participants' self-report negative experiences during emotion induction. Collectively, these data suggest that negative emotion influences how much and how well one can remember in WM. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Self-care or assisted PD: development of a new approach to evaluate manual peritoneal dialysis practice ability.

BACKGROUND: Peritoneal dialysis (PD) is a home-based therapy which requires the patients or their caregivers to perform the practice. We aimed to develop a practical approach to evaluate PD practice ability of the patients and to identify berries to self-care PD. METHODS: A structural form was designed comprising measures of physical, cognitive, and operational abilities which were required to perform manual PD independently. The evaluation was jointly conducted by a PD nurse, a nephrologist and a close family member of the patient. Patients who met all the requirements were deemed as capable of performing PD independently (self-care PD) and others were deemed as needing an assistant (assisted PD). RESULTS: The evaluation form was applied in 280 prevalent PD patients and 33.9% of them were assessed as needing assisted PD, mainly due to physical (62.1%) or operational (66.3%) disabilities. The evaluation result was consistent with current dialysis status in 79.3% patients and it matched better in patients who performed PD with the help of an assistant (93.0 vs. 76.8%, p = 0.014). Patients who were evaluated as having barriers to self-care PD but still performed PD without an assistant were older and demonstrated higher prevalence of diabetic nephropathy and PD-related infection, lower education level, and lower serum albumin (p < 0.05). CONCLUSIONS: The PD practice ability assessment form is useful to identify patients with barriers to self-care PD. It provides objective information to the patients and their family to choose feasible PD practice modality, self-care, or assisted PD.

Effects of sleep duration on neurocognitive development in early adolescents in the USA: a propensity score matched, longitudinal, observational study.

BACKGROUND: Although the American Academy of Sleep Medicine suggests at least 9 h of sleep per day for 6-12-year-olds, children in recent generations often report sleeping less than this amount. Because early adolescence is a crucial period for neurocognitive development, we aimed to investigate how insufficient sleep affects children's mental health, cognition, brain function, and brain structure over 2 years. METHODS: In this propensity score matched, longitudinal, observational cohort study, we obtained data from a population-based sample of 9-10-year-olds from 21 US study sites in the ongoing Adolescent Brain Cognitive Development (ABCD) study. Participants were categorised as having sufficient sleep or insufficient sleep on the basis of a cutoff of 9 h sleep per day. Using propensity score matching, we matched these two groups of participants on 11 key covariates, including sex, socioeconomic status, and puberty status. Participants were excluded from our analysis if they did not pass a baseline resting-state functional MRI quality check or had missing data for the covariates involved in propensity score matching. Outcome measures retrieved from the ABCD study were behavioural problems, mental health, cognition, and structural and resting-state functional brain measures, assessed at baseline and at 2-year follow-up. We examined group differences on these outcomes over those 2 years among all eligible participants. We then did mediation analyses of the neural correlates of behavioural changes induced by insufficient sleep. FINDINGS: Between Sept 1, 2016, and Oct 15, 2018, 11 878 individuals had baseline data collected for the ABCD study, of whom 8323 were eligible and included in this study (4142 participants in the sufficient sleep group and 4181 in the insufficient sleep group). Follow-up data were collected from July 30, 2018, to Jan 15, 2020. We identified 3021 matched sufficient sleep-insufficient sleep pairs at baseline and 749 matched pairs at 2-year follow-up, and observed similar differences between the groups in behaviour and neural measures at both timepoints; the effect sizes of between-group differences in behavioural measures at these two timepoints were significantly correlated with each other (r=0·85, 95% CI 0·73-0·92; p<0·0001). A similar pattern was observed in resting-state functional connectivity (r=0·54, 0·45-0·61; p<0·0001) and in structural measures (eg, in grey matter volume r=0·61, 0·51-0·69; p<0·0001). We found that cortico-basal ganglia functional connections mediate the effects of insufficient sleep on depression, thought problems, and crystallised intelligence, and that structural properties of the anterior temporal lobe mediate the effect of insufficient sleep on crystallised intelligence. INTERPRETATION: These results provide population-level evidence for the long-lasting effect of insufficient sleep on neurocognitive development in early adolescence. These findings highlight the value of early sleep intervention to improve early adolescents' long-term developmental outcomes. FUNDING: National Institutes of Health.

Solvent-Free Hydrogenation of 5-Hydroxymethylfurfural and Furfural to Furanyl Alcohols and their Self-Condensation Polymers.

2,5-Bis(hydroxymethyl)furan (BHMF) as well as furfuryl alcohol (FFA) are considered as highly valuable biomass-derived alcohols resembling aromatic monomers in polymer synthesis. Herein, a series of cobaltic nitrogen-doped carbon (Co-NC) catalysts calcinated at different temperatures were synthesized and tested for the solvent-free hydrogenation of 5-hydroxymethylfurfural (HMF) to prepare BHMF. It was found that the Co-NC catalyst calcinated at 600 °C (Co-NC-600) exhibited a superior catalytic activity in the hydrogenation reaction mainly due to the doping of graphitic N, which probably facilitated the polarization of H2 to afford H+ and H- . Consequently, Co-NC-600 offered a high BHMF/FFA yield greater than 90 % with a nearly complete conversion of HMF/furfural (FF) at the optimal conditions (80 °C, 4 h, and 5 MPa H2 ). After the hydrogenation reaction, Co-NC catalyst was facilely recycled by magnetic separation, and the obtained BHMF/FFA was then successfully transformed into hypercrosslinked polymers with an excellent CO2 /H2 storage capacity comparable to aromatic hydroxymethyl polymers. Therefore, this is a novel and facile two-step pathway for the conversion of biomass-derived HMF/FF towards functional polymers from both industrial and environmental perspectives.

Induced negative arousal modulates the speed of visual working memory consolidation.

This study examines how induced negative arousal influences the consolidation of fragile sensory inputs into durable working memory (WM) representations. Participants performed a visual WM change detection task with different amounts of encoding time manipulated by random pattern masks inserted at different levels of memory-and-mask Stimulus Onset Asynchrony (SOA). Prior to the WM task, negative or neutral emotion was induced using audio clips from the International Affective Digital Sounds (IADS). Pupillometry was simultaneously recorded to provide an objective measure of induced arousal. Self-report measures of early-life stress (i.e., adverse childhood experiences) and current mood states (i.e., depressed mood and anxious feeling) were also collected as covariates. We find that participants initially remember a comparable number of WM items under a short memory-and-mask SOA of 100 ms across emotion conditions, but then encode more items into WM at a longer memory-and-mask SOA of 333 ms under induced negative arousal. These findings suggest that induced negative arousal speeds up WM consolidation. Yet, induced negative arousal does not seem to significantly affect participants' WM storage capacity estimated from a separate no mask condition. Furthermore, this emotional effect on WM consolidation speed is moderated by key affect-related individual differences. Participants who have greater pupil responses to negative IADS sounds or have more early-life stress show faster WM consolidation under induced negative arousal. Collectively, our findings reveal a critical role of phasic adrenergic responses in the rapid consolidation of visual WM content and identify potential moderators of this association. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Visual and Semantic Contributions to Visual Short-Term Memory.

Liu et al. recently demonstrated novel neural evidence for visual and semantic contributions to the encoding and maintenance of object information in a delayed match-to-sample task. Their data highlight the close interaction between sensory experience and prior semantic knowledge in human visual short-term memory for naturalistic stimuli.