Rhythmic Activity Patterns Research Articles

People with HIV exhibit spectrally distinct patterns of rhythmic cortical activity serving cognitive flexibility

Despite effective antiretroviral therapy, cognitive impairment remains prevalent among people with HIV (PWH) and decrements in executive function are particularly prominent. One component of executive function is cognitive flexibility, which integrates a variety of executive functions to dynamically adapt one's behavior in response to changing contextual demands. Though substantial work has illuminated HIV-related aberrations in brain function, it remains unclear how the neural oscillatory dynamics serving cognitive flexibility are affected by HIV-related alterations in neural functioning. Herein, 149 participants (PWH: 74; seronegative controls: 75) between the ages of 29–76 years completed a perceptual feature matching task that probes cognitive flexibility during high-density magnetoencephalography (MEG). Neural responses were decomposed into the time-frequency domain and significant oscillatory responses in the theta (4–8 Hz), alpha (10–16 Hz), and gamma (74–98 Hz) spectral windows were imaged using a beamforming approach. Whole-brain voxel-wise comparisons were then conducted on these dynamic functional maps to identify HIV-related differences in the neural oscillatory dynamics supporting cognitive flexibility. Our findings indicated group differences in alpha oscillatory activity in the cingulo-opercular cortices, and differences in gamma activity were found in the cerebellum. Across all participants, alpha and gamma activity in these regions were associated with performance on the cognitive flexibility task. Further, PWH who had been treated with antiretroviral therapy for a longer duration and those with higher current CD4 counts had alpha responses that more closely resembled those of seronegative controls, suggesting that optimal clinical management of HIV infection is associated with preserved neural dynamics supporting cognitive flexibility.

Neocortical long-range inhibition promotes cortical synchrony and sleep.

Behavioral states such as sleep and wake are highly correlated with specific patterns of rhythmic activity in the cortex. During low arousal states such as slow wave sleep, the cortex is synchronized and dominated by low frequency rhythms coordinated across multiple regions. Although recent evidence suggests that GABAergic inhibitory neurons are key players in cortical state modulation, the in vivo circuit mechanisms coordinating synchronized activity among local and distant neocortical networks are not well understood. Here, we show that somatostatin and chondrolectin co-expressing cells (Sst-Chodl cells), a sparse and unique class of neocortical inhibitory neurons, are selectively active during low arousal states and are largely silent during periods of high arousal. In contrast to other neocortical inhibitory neurons, we show these neurons have long-range axons that project across neocortical areas. Activation of Sst-Chodl cells is sufficient to promote synchronized cortical states characteristic of low arousal, with increased spike co-firing and low frequency brain rhythms, and to alter behavioral states by promoting sleep. Contrary to the prevailing belief that sleep is exclusively driven by subcortical mechanisms, our findings reveal that these long-range inhibitory neurons not only track changes in behavioral state but are sufficient to induce both sleep-like cortical states and sleep behavior, establishing a crucial circuit component in regulating behavioral states.

Representations of imaginary scenes and their properties in cortical alpha activity

Imagining natural scenes enables us to engage with a myriad of simulated environments. How do our brains generate such complex mental images? Recent research suggests that cortical alpha activity carries information about individual objects during visual imagery. However, it remains unclear if more complex imagined contents such as natural scenes are similarly represented in alpha activity. Here, we answer this question by decoding the contents of imagined scenes from rhythmic cortical activity patterns. In an EEG experiment, participants imagined natural scenes based on detailed written descriptions, which conveyed four complementary scene properties: openness, naturalness, clutter level and brightness. By conducting classification analyses on EEG power patterns across neural frequencies, we were able to decode both individual imagined scenes as well as their properties from the alpha band, showing that also the contents of complex visual images are represented in alpha rhythms. A cross-classification analysis between alpha power patterns during the imagery task and during a perception task, in which participants were presented images of the described scenes, showed that scene representations in the alpha band are partly shared between imagery and late stages of perception. This suggests that alpha activity mediates the top-down re-activation of scene-related visual contents during imagery.

The influence of synaptic strength and noise on the robustness of central pattern generator

<abstract><p>In this paper, we explore the mechanisms of central pattern generators (CPGs), circuits that can generate rhythmic patterns of motor activity without external input. We study the half-center oscillator, a simple form of CPG circuit consisting of neurons connected by reciprocally inhibitory synapses. We examine the role of asymmetric coupling factors in shaping rhythm activity and how different network topologies contribute to network efficiency. We have discovered that neurons with lower synaptic strength are more susceptible to noise that affects rhythm changes. Our research highlights the importance of asymmetric coupling factors, noise, and other synaptic parameters in shaping the broad regimes of CPG rhythm. Finally, we compare three topology types' regular regimes and provide insights on how to locate the rhythm activity.</p></abstract>

Does exposure to moonlight affect day/night changes in melatonin and metabolic parameters in Amazonian fish?

Lunar cycle modulates the rhythmic activity patterns of many animals, including fish. The effect of the moonlight cycle on daily melatonin and metabolic parameters was evaluated in matrinxã (Brycon amazonicus) subjected to external natural lighting. Eighty juvenile were distributed in 4 tanks of 1m3 (20 fish/tank) and divided into two groups. One group was exposed to the full moon and the other group to the new moon for 30 days, which corresponds to the duration of the lunar period. At the end of the lunar phase, 6 fish from each group were anesthetized to collect blood, tissue and eye samples at midday and midnight. The comparison between the light and dark periods revealed a significant increase in plasma and ocular melatonin in the last period. However, there was no significant difference for plasma melatonin between moons. Ocular melatonin presented higher concentrations during the new moon. Glucose, total proteins, cortisol, liver glutathione and gill lipid peroxidation were higher in the full moon compared to in the new moon. Plasma triglyceride was higher during the night for the full moon, and the opposite was found for the new moon. Total cholesterol values were higher at night regardless the moon phase. Glutathione in the gills and lipid peroxidation in the liver showed no significant differences. These results highlight the importance of considering both the day and lunar cycles for melatonin and metabolic parameters in species of commercial interest and susceptible to stressful situations in rearing conditions.

Colony‐nesting gulls restrict activity levels of a native top carnivore during the breeding season

AbstractAlthough nesting in colonies can offer substantial reproductive benefits for many seabird species, increased visibility to predators remains a significant disadvantage for most colony‐breeders. To counteract this, some seabird species have evolved aggressive nest defense strategies to protect vulnerable eggs and chicks. Here, we used an experimental approach to test whether colony inhabitance by breeding gullsLarusspp. in western Norway impacts visitation rates of a native, mammalian predator, the Eurasian otterLutra lutraduring the breeding season. Camera traps were placed inside of and on the periphery of seabird colonies prior to the breeding season and left to run for one continuous year. Sighting frequency of otters on these cameras was compared to a control region free of gull nesting. We found that otter activity was significantly reduced in the colonies when gulls were incubating and rearing chicks, compared to time periods when gulls were building nests and absent from the colonies. Rhythmic activity patterns did not seem to be significantly impacted by the presence of gulls. This study provides clear evidence that certain colony‐nesting species can have a direct, negative impact on visitation rates of a native carnivore. Seasonal carnivore activity patterns are likely to be highly dependent on differing nesting strategies and level of nest defense by seabirds.

Endogenous rhythm variation and adaptation to the tidal environment in the freshwater snail, Semisulcospira reiniana

Organisms have endogenous timekeeping system(s) to coordinate their biological processes with environmental cycles, allowing adaptation to external rhythmic changes in their environment. The change in endogenous rhythms could contribute to range expansion in a novel rhythmic environment. We hypothesized that populations of the freshwater snail near estuaries show a circatidal rhythm to synchronize with the tidal cycle. We compared the behavioral and gene expression rhythms between non-tidal and tidal populations of the freshwater snail, Semisulcospira reiniana. Individuals inhabiting tidal areas exhibited a rhythmic activity pattern coordinated with the tidal cycle under both field and laboratory conditions, but individuals inhabiting upstream non-tidal areas showed a circadian activity pattern. The proportion of circadian oscillating genes was greater in non-tidal than in tidal individuals, while that of circatidal oscillating genes was greater in tidal than in non-tidal individuals. Additionally, transcriptome-wide population genetic analyses revealed that these two adjacent populations can be clearly distinguished genetically, though the genetic distance was very small. Our results provide evidence of the shift in an endogenous rhythm via range expansion to a novel rhythmic environment. The changes in a small number of genes and/or phenotypic plasticity may contribute to the difference in the endogenous rhythms between non-tidal and tidal populations.

Modulation of cortical beta oscillations influences motor vigor: A rhythmic TMS-EEG study.

Previous electro- or magnetoencephalography (Electro/Magneto EncephaloGraphic; E/MEG) studies using a correlative approach have shown that β (13-30 Hz) oscillations emerging in the primary motor cortex (M1) are implicated in regulating motor response vigor and associated with an anti-kinetic role, that is, slowness of movement. However, the functional role of M1 β oscillations in regulation of motor responses remains unclear. To address this gap, we combined EEG with rhythmic TMS (rhTMS) delivered to M1 at the β (20 Hz) frequency shortly before subjects performed an isometric ramp-and-hold finger force production task at three force levels. rhTMS is a novel approach that can modulate rhythmic patterns of neural activity. β-rhTMS over M1 induced a modulation of neural oscillations to β frequency in the sensorimotor area and reduced peak force rate during the ramp-up period relative to sham and catch trials. Interestingly, this rhTMS effect occurred only in the large force production condition. To distinguish whether the effects of rhTMS on EEG and behavior stemmed from phase-resetting by each magnetic pulse or neural entrainment by the periodicity of rhTMS, we performed a control experiment using arrhythmic TMS (arTMS). arTMS did not induce changes in EEG oscillations nor peak force rate during the rump-up period. Our results provide novel evidence that β neural oscillations emerging the sensorimotor area influence the regulation of motor response vigor. Furthermore, our findings further demonstrate that rhTMS is a promising tool for tuning neural oscillations to the target frequency.

Host circadian behaviors exert only weak selective pressure on the gut microbiome under stable conditions but are critical for recovery from antibiotic treatment.

The circadian rhythms of hosts dictate an approximately 24 h transformation in the environment experienced by their gut microbiome. The consequences of this cyclic environment on the intestinal microbiota are barely understood and are likely to have medical ramifications. Can daily rhythmicity in the gut act as a selective pressure that shapes the microbial community? Moreover, given that several bacterial species have been reported to exhibit circadian rhythms themselves, we test here whether a rhythmic environment is a selective pressure that favors clock-harboring bacteria that can anticipate and prepare for consistent daily changes in the environment. We observed that the daily rhythmicity of the mouse gut environment is a stabilizing influence that facilitates microbiotal recovery from antibiotic perturbation. The composition of the microbiome recovers to pretreatment conditions when exposed to consistent daily rhythmicity, whereas in hosts whose feeding and activity patterns are temporally disrupted, microbiotal recovery is incomplete and allows potentially unhealthy opportunists to exploit the temporal disarray. Unexpectedly, we found that in the absence of antibiotic perturbation, the gut microbiome is stable to rhythmic versus disrupted feeding and activity patterns. Comparison of our results with those of other studies reveals an intriguing correlation that a stable microbiome may be resilient to one perturbation alone (e.g., disruption of the daily timing of host behavior and feeding), but not to multiple perturbations in combination. However, after a perturbation of the stable microbiome, a regular daily pattern of host behavior/feeding appears to be essential for the microbiome to recover to the original steady state. Given the inconsistency of daily rhythms in modern human life (e.g., shiftwork, social jet-lag, irregular eating habits), these results emphasize the importance of consistent daily rhythmicity to optimal health not only directly to the host, but also indirectly by preserving the host's microbiome in the face of perturbations.

Generation and Characterization of a Novel Angelman Syndrome Mouse Model with a Full Deletion of the Ube3a Gene.

Angelman syndrome (AS) is a neurodevelopmental disorder caused by deficits in maternally inherited UBE3A. The disease is characterized by intellectual disability, impaired motor skills, and behavioral deficits, including increased anxiety and autism spectrum disorder features. The mouse models used so far in AS research recapitulate most of the cardinal AS characteristics. However, they do not mimic the situation found in the majority of AS patients who have a large deletion spanning 4–6 Mb. There is also a large variability in phenotypes reported in the available models, which altogether limits development of therapeutics. Therefore, we have generated a mouse model in which the Ube3a gene is deleted entirely from the 5′ UTR to the 3′ UTR of mouse Ube3a isoform 2, resulting in a deletion of 76 kb. To investigate its phenotypic suitability as a model for AS, we employed a battery of behavioral tests directed to reveal AS pathology and to find out whether this model better mirrors AS development compared to other available models. We found that the maternally inherited Ube3a-deficient line exhibits robust motor dysfunction, as seen in the rotarod and DigiGait tests, and displays abnormalities in additional behavioral paradigms, including reduced nest building and hypoactivity, although no apparent cognitive phenotype was observed in the Barnes maze and novel object recognition tests. The AS mice did, however, underperform in more complex cognition tasks, such as place reversal in the IntelliCage system, and exhibited a different circadian rhythm activity pattern. We show that the novel UBE3A-deficient model, based on a whole-gene deletion, is suitable for AS research, as it recapitulates important phenotypes characteristic of AS. This new mouse model provides complementary possibilities to study the Ube3a gene and its function in health and disease as well as possible therapeutic interventions to restore function.

The rhythm of the night: patterns of activity of the European wildcat in the Italian peninsula

The European wildcat is a threatened carnivore, whose ecology is still scarcely studied, especially in Mediterranean areas. In this study, we estimated activity rhythm patterns of this felid, by means of camera-trapping at three spatial scales: (i) whole country (Italy); (ii) biogeographical areas; (iii) latitudinal zones. The activity rhythms patterns were also calculated according to temporal scales: (1) warm semester; (2) cold semester and (3) seasonal scales. Lastly, we also tested whether the effect of moon phases affected the wildcat activity. We conducted the analysis on a total of 975 independent events collected in 2009–2021, from 285 locations, in ~ 65,800 camera days. We showed that the wildcat in Italy exhibits a > 70% nocturnal behaviour, with 20% of diurnal activity, at all spatial scales, and throughout the whole year, with peaks at 10.00 p.m. and 04.00 a.m. We observed a high overlap of wildcat activity rhythms between different biogeographical and latitudinal zones. The wildcat was mainly active on the darkest nights, reducing its activity in bright moonlight nights. Diurnal activity was greater in the warm months and decreased with the distance from shrubs and woodlands, most likely according to activity rhythms of its main prey, water presence in summer, the care of offspring and the availability of shelter sites. Conversely, the distance to paved roads seems to have no significant effects on diurnal activity, suggesting that, in presence of natural shelters, the wildcat probably may tolerate these infrastructures. We suggested limited plasticity in activity rhythm patterns of the wildcat, emphasizing the importance of dark hours for this species.

Gastrointestinal Myoelectric Measurements via Simultaneous External and Internal Electrodes in Pigs

IntroductionCurrently, there is no accurate noninvasive measurement system to diagnose gastrointestinal (GI) motility disorders. Wireless skin patches have been introduced to provide an accurate noninvasive measurement of GI myoelectric activity which is essential for developing neuro-stimulation devices to treat GI motility disorders. The aim of this study is to compare the external and internal electrical signal measurements in ambulatory pigs. MethodsYucatan pigs underwent placement of internal electrodes on the stomach, small intestine, and colon. Wires were brought through the abdominal wall. Signals were collected by a wireless receptor. Four external patches were placed on the abdominal skin to record the signals simultaneously. Pigs were kept for 6 d while the sensors were continuously recording the data from both systems. ResultsInternal sensors detected rich signals from each organ. The stomach had a dominant frequency that ranged from 4 to 4.5 cpm, with occasional higher frequencies at 2, 3 and 4 times that. Small intestine signals had their primary energy in the 12-15 cpm range. Colon signals primarily displayed a dominant broad peak in the 4-6 cpm region. External skin patches detected a substantial fraction of the activities measured by the internal electrodes. A clear congruence in the frequency spectrum was observed between the internal and external readings. ConclusionsInternally measured myoelectrical signals confirmed different patterns of rhythmic activity of the stomach, small intestine, and colon. Skin patches provided GI myoelectric measurement with a range of frequencies that could be useful in the diagnosis and treatment of motility disorders.

Restoring the dampened expression of the core clock molecule BMAL1 protects against compression-induced intervertebral disc degeneration

The circadian clock participates in maintaining homeostasis in peripheral tissues, including intervertebral discs (IVDs). Abnormal mechanical loading is a known risk factor for intervertebral disc degeneration (IDD). Based on the rhythmic daily loading pattern of rest and activity, we hypothesized that abnormal mechanical loading could dampen the IVD clock, contributing to IDD. Here, we investigated the effects of abnormal loading on the IVD clock and aimed to inhibit compression-induced IDD by targeting the core clock molecule brain and muscle Arnt-like protein-1 (BMAL1). In this study, we showed that BMAL1 KO mice exhibit radiographic features similar to those of human IDD and that BMAL1 expression was negatively correlated with IDD severity by systematic analysis based on 149 human IVD samples. The intrinsic circadian clock in the IVD was dampened by excessive loading, and BMAL1 overexpression by lentivirus attenuated compression-induced IDD. Inhibition of the RhoA/ROCK pathway by Y-27632 or melatonin attenuated the compression-induced decrease in BMAL1 expression. Finally, the two drugs partially restored BMAL1 expression and alleviated IDD in a diurnal compression model. Our results first show that excessive loading dampens the circadian clock of nucleus pulposus tissues via the RhoA/ROCK pathway, the inhibition of which potentially protects against compression-induced IDD by preserving BMAL1 expression. These findings underline the importance of the circadian clock for IVD homeostasis and provide a potentially effective therapeutic strategy for IDD.

Contributions of h- and Na+/K+ Pump Currents to the Generation of Episodic and Continuous Rhythmic Activities.

Developing spinal motor networks produce a diverse array of outputs, including episodic and continuous patterns of rhythmic activity. Variation in excitability state and neuromodulatory tone can facilitate transitions between episodic and continuous rhythms; however, the intrinsic mechanisms that govern these rhythms and their transitions are poorly understood. Here, we tested the capacity of a single central pattern generator (CPG) circuit with tunable properties to generate multiple outputs. To address this, we deployed a computational model composed of an inhibitory half-center oscillator (HCO). Following predictions of our computational model, we tested the contributions of key properties to the generation of an episodic rhythm produced by isolated spinal cords of the newborn mouse. The model recapitulates the diverse state-dependent rhythms evoked by dopamine. In the model, episodic bursting depended predominantly on the endogenous oscillatory properties of neurons, with Na+/K+ ATPase pump (IPump) and hyperpolarization-activated currents (Ih) playing key roles. Modulation of either IPump or Ih produced transitions between episodic and continuous rhythms and silence. As maximal activity of IPump decreased, the interepisode interval and period increased along with a reduction in episode duration. Decreasing maximal conductance of Ih decreased episode duration and increased interepisode interval. Pharmacological manipulations of Ih with ivabradine, and IPump with ouabain or monensin in isolated spinal cords produced findings consistent with the model. Our modeling and experimental results highlight key roles of Ih and IPump in producing episodic rhythms and provide insight into mechanisms that permit a single CPG to produce multiple patterns of rhythmicity.

Assessing Sex-Specific Circadian, Metabolic, and Cognitive Phenotypes in the AβPP/PS1 and APPNL-F/NL-F Models of Alzheimer's Disease.

Circadian disruption has long been recognized as a symptom of Alzheimer's disease (AD); however, emerging data suggests that circadian dysfunction occurs early on in disease development, potentially preceding any noticeable cognitive deficits. This study compares the onset of AD in male and female wild type (C57BL6/J), transgenic (AβPP/PS1), and knock-in (APPNL-F/NL-F) AD mouse models from the period of plaque initiation (6 months) through 12 months. Rhythmic daily activity patterns, glucose sensitivity, cognitive function (Morris water maze, MWM), and AD pathology (plaques formation) were assessed. A comparison was made across sexes. Sex-dependent hyperactivity in AβPP/PS1 mice was observed. In comparison to C57BL/6J animals, 6-month-old male AβPP/PS1 demonstrated nighttime hyperactivity, as did 12-month-old females. Female AβPP/PS1 animals performed significantly worse on a MWM task than AβPP/PS1 males at 12 months and trended toward increased plaque pathology. APPNL-F/NL-F 12-month-old males performed significantly worse on the MWM task compared to 12-month-old females. Significantly greater plaque pathology occurred in AβPP/PS1 animals as compared to APPNL-F/NL-F animals. Female AβPP/PS1 animals performed significantly worse than APPNL-F/NL-F animals in spatial learning and memory tasks, though this was reversed in males. Taken together, this study provides novel insights into baseline sex differences, as well as characterizes baseline diurnal activity variations, in the AβPP/PS1 and APPNL-F/NL-F AD mouse models.

Photoperiodic light pulse induces ovarian development in the catfish, Mystus cavasius: Possible roles of dopamine and melatonin in the brain

In the freshwater catfish, Mystus cavasius, locally known as gulsha, ovarian maturation is triggered by long-day conditions. Using dopaminergic neuronal activity in the brain, the purpose of this study was to identify the brain’s detection of a nocturnal light pulse that induced ovarian development. Since direct inhibition of pituitary gonadotropin release is exerted by dopamine (DA), it may serve as a neuromodulator of photoperiodic stimulation in teleosts. We studied functional effects of photoperiodicity on dopaminergic rhythmicity in gulsha brain. Nocturnal illumination and Nanda-Hamner photocycles revealed that ovarian development is induced by a 1 h light pulse between zeitgeber time (ZT) 12 and 13. Daily fluctuations in DA, 3, 4-dihydroxyphenylacetic acid (DOPAC) and DOPAC/DA were observed under a 12L:12D photoperiod. Fish exhibited increased levels during the daytime and decreased levels at night. Rhythmic patterns of dopaminergic activity also showed clear circadian oscillations under constant light, but not constant dark conditions. After 7 days of exposure to long photoperiod (14L:10D), DA, DOPAC and DOPAC/DA in the brain at ZT12 and ZT16 were significantly higher than during a short photoperiod (10L:14D). Melatonin-containing water inhibited the release of DA and DOPAC 6 h and 24 h after treatment, respectively, and DOPAC/DA 6 h after treatment. This inhibition was blocked by the melatonin receptor antagonist, luzindole. These results suggest that a 1 h nocturnal light pulse induces ovarian development through alteration of dopaminergic neuronal excitability in the brain, via oscillation in melatonin triggered by photic stimuli, which may interfere with the reproductive endocrine axis in gulsha.

Temporal Relations between Cortical Network Oscillations and Breathing Frequency during REM Sleep.

Nasal breathing generates a rhythmic signal which entrains cortical network oscillations in widespread brain regions on a cycle-to-cycle time scale. It is unknown, however, how respiration and neuronal network activity interact on a larger time scale: are breathing frequency and typical neuronal oscillation patterns correlated? Is there any directionality or temporal relationship? To address these questions, we recorded field potentials from the posterior parietal cortex of mice together with respiration during REM sleep. In this state, the parietal cortex exhibits prominent θ and γ oscillations while behavioral activity is minimal, reducing confounding signals. We found that the instantaneous breathing frequency strongly correlates with the instantaneous frequency and amplitude of both θ and γ oscillations. Cross-correlograms and Granger causality revealed specific directionalities for different rhythms: changes in θ activity precede and Granger-cause changes in breathing frequency, suggesting control by the functional state of the brain. On the other hand, the instantaneous breathing frequency Granger causes changes in γ frequency, suggesting that γ is influenced by a peripheral reafference signal. These findings show that changes in breathing frequency temporally relate to changes in different patterns of rhythmic brain activity. We hypothesize that such temporal relations are mediated by a common central drive likely to be located in the brainstem.

Closed-Loop Transcranial Alternating Current Stimulation: Towards Personalized Non-invasive Brain Stimulation for the Treatment of Psychiatric Illnesses

This review introduces closed-loop transcranial alternating current stimulation (tACS), which has the potential to become an effective and safe treatment modality for psychiatric illnesses such as schizophrenia and depression. The weak electric fields delivered to the brain by transcranial current stimulation interact in a synergistic manner with endogenous rhythmic brain activity patterns. As a result, the effect of stimulation on neuronal network dynamics is state dependent. Therefore, closed-loop paradigms that measure brain activity and apply targeted stimulation based on these measurements may allow effective modulation by targeted low-amplitude stimulation that is tuned to modulate the measured activity. Few initial studies of such closed-loop tACS have recently documented successful target engagement, mostly for applications that target specific activity patterns during sleep. Given the urgent need of novel therapeutic interventions for psychiatric disorders and the recent promising data from initial tACS clinical trials in psychiatry, we propose that closed-loop tACS deserves attention as a promising personalized medicine strategy in psychiatry.

Spatio-spectral relationships between pathological neural dynamics and cognitive impairment along the Alzheimer's disease spectrum.

IntroductionNumerous studies have described aberrant patterns of rhythmic neural activity in patients along the Alzheimer's disease (AD) spectrum, yet the relationships between these pathological features and cognitive decline are uncertain.MethodsWe acquired magnetoencephalography (MEG) data from 38 amyloid‐PET biomarker‐confirmed patients on the AD spectrum and a comparison group of biomarker‐negative cognitively normal (CN) healthy adults, alongside an extensive neuropsychological battery.ResultsBy modeling whole‐brain rhythmic neural activity with an extensive neuropsychological profile in patients on the AD spectrum, we show that the spectral and spatial features of deviations from healthy adults in neural population‐level activity inform their relevance to domain‐specific neurocognitive declines.DiscussionRegional oscillatory activity represents a sensitive metric of neuronal pathology in patients on the AD spectrum. By considering not only the spatial, but also the spectral, definitions of cortical neuronal activity, we show that domain‐specific cognitive declines can be better modeled in these individuals.

Blessing the rains down in Africa: spatiotemporal behaviour of the crested porcupine <em>Hystrix cristata</em> (Mammalia: Rodentia) in the rainy and dry seasons, in the African savannah

The assessment of habitat selection and temporal patterns of activity rhythms is paramount for wildlife conservation. Studies on behavioural ecology of wild mammals are particularly challenging in tropical areas, mostly when involving rare or elusive species. Despite being a common species in Italy, the crested porcupine Hystrix cristata is threatened of extinction throughout most of its sub-Saharan range. All available information on the ecology of this species has been collected in Italy, whereas no data is present in the scientific literature on spatiotemporal behaviour of this large rodent in Africa. In this work, we attempted to determine habitat selection and temporal patterns of activity rhythms of the crested porcupine in northern Benin and neighbouring countries, through intensive camera-trapping. We collected a total of 146 records of crested porcupine, 91 in the dry season (October-March) and 55 in the rainy season (April-September). Porcupines used most habitats in proportion to their local availability, while selecting rock outcrop formations (possibly used as shelter sites) and avoiding open areas, wetlands and gallery forests. A mostly nocturnal behaviour was confirmed throughout the year, with some diurnal activity at the start and at the end of the rainy season. The importance of rains in determining birth peak has been also showed, with juvenile individuals always observed at the start and at the end of the rainy season. Full moon always inhibited activity of this large rodent, most likely evolved as an antipredatory behaviour to limit encounters with potential predators (common leopard Panthera pardus, spotted hyaena Crocuta crocuta and honey badger Mellivora capensis) and humans. Poaching pressure towards porcupines in West Africa is strong. Porcupines are killed for the traditional medicine, for their meat and because they are widely considered as a crop pest. This assessment should therefore be used as a basic tool to design conservation plans to preserve this rodent species in its native range.