Population Vector Research Articles

Perpetual step-like restructuring of hippocampal circuit dynamics

Representation of the environment by hippocampal populations is known to drift even within a familiar environment, which could reflect gradual changes in single-cell activity or result from averaging across discrete switches of single neurons. Disambiguating these possibilities is crucial, as they each imply distinct mechanisms. Leveraging change point detection and model comparison, we find that CA1 population vectors decorrelate gradually within a session. In contrast, individual neurons exhibit predominantly step-like emergence and disappearance of place fields or sustained changes in within-field firing. The changes are not restricted to particular parts of the maze or trials and do not require apparent behavioral changes. The same place fields emerge, disappear, and reappear across days, suggesting that the hippocampus reuses pre-existing assemblies, rather than forming new fields de novo. Our results suggest an internally driven perpetual step-like reorganization of the neuronal assemblies.

Mathematical Model for Describing the Transmission of Animal African Trypanosomiasis in Cattle

In this paper, we have formulated a mathematical model for the transmission dynamics of African Animal Trypanosomiasis (AAT) by incorporating spraying of the tsetse y population(vector) and treating the cattle population (host) as control strategies. It has been shown that the disease free equilibrium point is globally asymptotically stable and the endemic equilibrium point is locally asymptotically stable. We have also shown that treatment of the host population reduces significantly infection by AAT as compared to spraying of the vector population.

Single trial Bayesian inference by population vector readout in the barn owl's sound localization system.

Bayesian models have proven effective in characterizing perception, behavior, and neural encoding across diverse species and systems. The neural implementation of Bayesian inference in the barn owl's sound localization system and behavior has been previously explained by a non-uniform population code model. This model specifies the neural population activity pattern required for a population vector readout to match the optimal Bayesian estimate. While prior analyses focused on trial-averaged comparisons of model predictions with behavior and single-neuron responses, it remains unknown whether this model can accurately approximate Bayesian inference on single trials under varying sensory reliability, a fundamental condition for natural perception and behavior. In this study, we utilized mathematical analysis and simulations to demonstrate that decoding a non-uniform population code via a population vector readout approximates the Bayesian estimate on single trials for varying sensory reliabilities. Our findings provide additional support for the non-uniform population code model as a viable explanation for the barn owl's sound localization pathway and behavior.

Mu-ERD reflects action understanding, but the effect is small

Since the mid-2000’s, many researchers have provided evidence that mu-ERD measured at the motor cortex may reflect the collective activation of upstream brain regions associated with the human mirror system during action observation paradigms; however, several recent papers have called these findings into question. Our study represents an effort to address these criticisms. In our study, participants watched videos in which the type of grip an actor used to grasp a coffee mug either conveyed the goal with 100 % certainty (unambiguous-goal trials), or offered no predictive information (ambiguous-goal trials). If mu-ERD indexes action understanding, then we predicted that mu-ERD should increase while participants watched the actor grasp the mug for unambiguous-goal trials, but not for ambiguous-goal trials. During the intervals where participants watched the actor execute the goal, mu-ERD for unambiguous-goal trials should remain steady, whereas mu-ERD for ambiguous-goal trials should now increase. Conversely, if mu-ERD does not index action understanding, and instead reflects general motor processes associated with action (such as the activation of population vectors in M1 or planning processes), then mu-ERD should show no difference across conditions. Across most comparisons, we found that mu-ERD mostly reflected general motor processes; however, there was a small effect when participants overserved unambiguous-goal trials while watching the actor execute the goal suggesting that mu-ERD does reflect mirroring, but the effect is small.

Dynamics of space coding by mouse hippocampal CA1 field neurons in a free navigation task in different environments

The development of persistent cognitive adaptations in neurons is a key area of focus in contemporary neuroscience. A significant illustration of such adaptations occurs through spatial specializations in place cells with one or more receptive fields that are sensitive to spatial cues (place fields) [1]. In prior research, we extensively examined the dynamics of place field formation in granular layer neurons of the CA1 field in the hippocampus of mice during arbitrary free navigation in a circular track [2]. As the primary factor for maintaining stability in the spatial specialization of place cells, we have introduced dynamic selectivity. This approach enables us to monitor the latency of each place field’s formation and the selectivity dynamics of place cells to their respective fields throughout one or multiple shooting sessions. However, in one-dimensional settings, like the circular track referenced previously, place fields can demonstrate direction-specificity with regards to animal movement [3]. This factor considerably complicates the analysis for arbitrary movement trajectories of animals. In this study, additional experiments were conducted to capture the neural activity of mice in two-dimensional environments. The experiments were conducted in both a rectangular field with objects and a circular arena with a varying number of obstacles. In this paper, we conduct a comparative analysis to examine the critical parameters governing the development of spatial specializations in a one-dimensional circle track and two-dimensional arenas. These parameters include specialization latency, average dynamic selectivity, initial increase in selectivity, and the proportion of “immediate” place fields that remain stable from the first animal visit. The study discovered that the mean selectivity of the place fields escalated in each session, with higher rates observed in subsequent sessions versus the initial session in a novel setting. Additionally, there was a significant occurrence of “immediate” place fields, representing 11% of all place fields in the rounded arena with obstacles, and 25% of all place fields in the circular track. Additionally, a population analysis of neural activity was performed on the first session in a circular track and a round arena with obstacles. Using Laplace eigenmaps for the dimension reduction of population vectors, the trajectory of animals was reconstructed, and the accuracy of this reconstruction agreed with the average dynamic selectivity for each animal included in the analysis. Thus, dynamic selectivity was verified as a measure of the spatial coding quality of the entire registered population of neurons.

Research on Quantization Parameter Decision Scheme for High Efficiency Video Coding

High-Efficiency Video Coding (HEVC) is one of the most widely studied coding standards. It still uses the block-based hybrid coding framework of Advanced Video Coding (AVC), and compared to AVC, it can double the compression ratio while maintaining the same quality of reconstructed video. The quantization module is an important module in video coding. In the process of quantization, quantization parameter is an important factor in determining the bitrate in video coding, especially in the case of limited channel bandwidth. It is particularly important to select a reasonable quantization parameter to make the bitrate as close as possible to the target bitrate. Aiming at the problem of unreasonable selection of quantization parameters in codecs, this paper proposes using a differential evolution algorithm to assign quantization parameter values to the coding tree unit (CTU) in each frame of 360-degree panoramic video based on HEVC so as to strike a balance between bitrate and distortion. Firstly, the number of CTU rows in a 360-degree panoramic video frame is considered as the dimension of the optimization problem. Then, a trial vector is obtained by randomly selecting the vectors in the population for mutation and crossover. In the mutation step, the algorithm generates a new parameter vector by adding the weighted difference between two population vectors to a third vector. And the elements in the new parameter vector are selected according to the crossover rate. Finally, the trial vector is regarded as the quantization parameter of each CTU in the CTU row to encode, and the vector with the least rate distortion is selected. The algorithm will produce the optimal quantization parameter combination for the current video. The experimental results show that compared to the benchmark algorithm of HEVC reference software HM-16.20, the proposed algorithm can provide a bit saving of 1.86%, while the peak signal-to-noise ratio (PSNR) can be improved by 0.07 dB.

All-optical recreation of naturalistic neural activity with a multifunctional transgenic reporter mouse

Determining which features of the neural code drive behavior requires the ability to simultaneously read out and write in neural activity patterns with high precision across many neurons. All-optical systems that combine two-photon calcium imaging and targeted photostimulation enable the activation of specific, functionally defined groups of neurons. However, these techniques are unable to test how patterns of activity across a population contribute to computation because of an inability to both read and write cell-specific firing rates. To overcome this challenge, we make two advances: first, we introduce a genetic line of mice for Cre-dependent co-expression of a calcium indicator and a potent soma-targeted microbial opsin. Second, using this line, we develop a method for read-out and write-in of precise population vectors of neural activity by calibrating the photostimulation to each cell. These advances offer a powerful and convenient platform for investigating the neural codes of computation and behavior.

Hippocampal place cell remapping occurs with memory storage of aversive experiences.

Aversive stimuli can cause hippocampal place cells to remap their firing fields, but it is not known whether remapping plays a role in storing memories of aversive experiences. Here we addressed this question by performing in-vivo calcium imaging of CA1 place cells in freely behaving rats (n=14). Rats were first trained to prefer a short path over a long path for obtaining food reward, then trained to avoid the short path by delivering a mild footshock. Remapping was assessed by comparing place cell population vector similarity before acquisition versus after extinction of avoidance. Some rats received shock after systemic injections of the amnestic drug scopolamine at a dose (1 mg/kg) that impaired avoidance learning but spared spatial tuning and shock-evoked responses of CA1 neurons. Place cells remapped significantly more following remembered than forgotten shocks (drug-free versus scopolamine conditions); shock-induced remapping did not cause place fields to migrate toward or away from the shocked location and was similarly prevalent in cells that were responsive versus non-responsive to shocks. When rats were exposed to a neutral barrier rather than aversive shock, place cells remapped significantly less in response to the barrier. We conclude that place cell remapping occurs in response to events that are remembered rather than merely perceived and forgotten, suggesting that reorganization of hippocampal population codes may play a role in storing memories for aversive events.

Genetic Differentiation of Aedes aegypti (Diptera: Culicidae) in Areas with High Rates of Infestation in Mid-North Region of Brazil.

Aedes aegypti is the principal vector of the arboviruses-yellow fever, dengue virus, chikungunya, and zika virus. Given the epidemiological importance of this mosquito, its capacity to adapt to different habitats, and its resistance to many types of control measures, systematic research into the genetic variability of the populations of this mosquito is one of the most important steps toward a better understanding of its population structure and vector competence. In this context, the present study verified the presence of distinct genetic lineages of Ae. aegypti in areas with high infestation rates, based on the analysis of microsatellite markers. The samples were collected in nine municipalities with high building infestation rates in the Mid-North region of Brazil. Six microsatellite loci were genotyped in the 138 samples, producing a total of 32 alleles, varying from one to nine alleles per locus in each of the different populations. The AMOVA revealed greater within-population genetic differentiation with high fixation rates. The general analysis of population structure, based on a Bayesian approach, revealed K = 2, with two Ae. aegypti lineages that were highly differentiated genetically. These data on the connectivity of the populations and the genetic isolation of the lineages provide important insights for the development of innovative strategies for the control of the populations of this important disease vector.

Predicting dengue incidence using panel data analysis

Dengue is the most rapidly spreading infectious disease, especially in Indonesia. Dengue virus is transmitted by the bite of female Aedes mosquitoes. The high human population density and proximity to vector breeding places strengthen the interaction between the virus, vector, and humans as hosts. Using dengue incidence panel data during 2018-2019 in 34 provinces in Indonesia, this study examined the effect of human population density as a demographic variable and vector control on dengue incidence in Indonesia. The time series data were analyzed using EViews. The fixed effect model estimation showed that dengue incidence was significantly associated with demographic variables measured as human population density, with a P-value of 0.02. The vector control variable shows an insignificant association with dengue incidence. But simultaneous analysis between human population density and vector control on dengue incidence has a significant association with probability F (statistic) = 0.000. Our study demonstrated that densely populated provinces in Indonesia have a very high incidence of dengue. Improving sanitation in densely populated settlements can prevent and control dengue incidence.

지역활성화를 위한 준공업지역의 상업 공간 분포 특성 비교 연구 - 성수동2가와 문래동을 중심으로 -

Mullae-dong and Seongsu-dong (2ga) are the same semi-industrial and urban regeneration areas that are turning into commercial spaces. But Seongsu-dong is higher in the total of de facto population and is full of energetic young people in their 20s to 40s compared to Mullae-dong. This study aims to suggest the new direction of regeneration for the Mullae-dong by comparing the differences in the pattern of spatial distribution that can increase the activity and mobility of population based on the diversity of space types and the density of commercial spaces. This study compared the diversity, density and clustering of commercial spaces in two areas using Q-GIS. For analyzing, the de facto population vector data and commercial space point data were overlapped, and then the spatial data was re-extracted. The result shows that in spite of the high population density of young people, Mullae-dong is less energetic place than Seongsu-dong due to the lack of diversity and the low density of commercial spaces. It means that Mullae-dong is needed to revitalize commercial districts for the regional regeneration.

Nucleic Acid Prevalence of Zoonotic Babesia in Humans, Animals and Questing Ticks, a Systematic Review and Meta-Analysis

Background: Zoonotic Babesia infections are an emerging public health threat globally. The geographical distribution, animal reservoirs and tick vectors vary greatly across Babesia species, and estimations of prevalence reported in works within the literature are also quite different. Better prevalence estimates and identification of moderators are needed to understand the global transmission risk of different zoonotic Babesia species, and to provide crucial background information for the diagnosis, treatment and control of zoonotic babesiosis. Methods: We conducted a systematic review and meta-analysis to determine the global nucleic acid prevalence of different zoonotic Babesia species in humans, animals and ticks. Relevant publications were obtained from several electronic databases and grey literature up to December 2021. Articles were included if they were published in English or Chinese and reported the nucleic acid prevalence of zoonotic Babesia species in humans, animals or ticks. The pooled estimates of prevalence were determined using a random effect model. Heterogeneity was investigated using subgroup analyses and random effect meta-regression models. Results: Of 3205 unique studies, 28 were included by the systematic review of zoonotic Babesia for humans, 79 for animals and 104 for ticks. The results showed overall pooled estimates of nucleic acid prevalence for the following: B. microti-1.93% (0.32-4.69%) in humans; B. microti-7.80% (5.25-10.77%), B. divergens-2.12% (0.73-4.08%) and B. venatorum-1.42% (0.30-3.16%) in animals; and B. microti-2.30% (1.59-3.13%), B. divergens-0.16% (0.05-0.32%), and B. venatorum-0.39% (0.26-0.54%) in questing ticks. The type of population, animal reservoir or tick vector, detecting method and continent were moderators possibly associated with heterogeneity, yet the remaining heterogeneity that was not explained was still substantial (all QE p values < 0.05). Conclusions:B. microti is the most prevalent and widely distributed zoonotic Babesia species globally. The wide range of suitable animal reservoirs and potential transmission vectors and high prevalence in animals and ticks may contribute to the worldwide distribution of B. microti. Other zoonotic Babesia species were relatively less prevalent and were reported in quite limited areas.

Context-independent expression of spatial code in hippocampus

The hippocampus plays a crucial role in the formation and retrieval of spatial memory across mammals and episodic memory in humans. Episodic and spatial memories can be retrieved irrespective of the subject’s awake behavioral state and independently of its actual spatial context. However, the nature of hippocampal network activity during such out-context retrieval has not been described so far. Theoretically, context-independent spatial memory retrieval suggests a shift of the hippocampal spatial representations from coding the current spatial context to coding the remembered environment. In this study we show in rats that the CA3 neuronal population can switch spontaneously across representations and transiently activate another stored familiar spatial pattern without direct external sensory cuing. This phenomenon qualitatively differs from the well-described sharp wave-related pattern reactivations during immobility. Here, it occurs under the theta oscillatory state during active exploration and reflects the preceding experience of sudden environmental change. The respective out-context coding spikes appeared later in the theta cycle than the in-context ones. Finally, the experience also induced the emergence of population vectors with a co-expression of both codes segregated into different phases of the theta cycle.

Conceptual framework for neuronal ensemble identification and manipulation related to behavior using calcium imaging.

.SignificanceThe identification and manipulation of spatially identified neuronal ensembles with optical methods have been recently used to prove the causal link between neuronal ensemble activity and learned behaviors. However, the standardization of a conceptual framework to identify and manipulate neuronal ensembles from calcium imaging recordings is still lacking.AimWe propose a conceptual framework for the identification and manipulation of neuronal ensembles using simultaneous calcium imaging and two-photon optogenetics in behaving mice.ApproachWe review the computational approaches that have been used to identify and manipulate neuronal ensembles with single cell resolution during behavior in different brain regions using all-optical methods.ResultsWe proposed three steps as a conceptual framework that could be applied to calcium imaging recordings to identify and manipulate neuronal ensembles in behaving mice: (1) transformation of calcium transients into binary arrays; (2) identification of neuronal ensembles as similar population vectors; and (3) targeting of neuronal ensemble members that significantly impact behavioral performance.ConclusionsThe use of simultaneous two-photon calcium imaging and two-photon optogenetics allowed for the experimental demonstration of the causal relation of population activity and learned behaviors. The standardization of analytical tools to identify and manipulate neuronal ensembles could accelerate interventional experiments aiming to reprogram the brain in normal and pathological conditions.

Hippocampal place cells have goal-oriented vector fields during navigation

The hippocampal cognitive map supports navigation towards, or away from, salient locations in familiar environments1. Although much is known about how the hippocampus encodes location in world-centred coordinates, how it supports flexible navigation is less well understood. We recorded CA1 place cells while rats navigated to a goal on the honeycomb maze2. The maze tests navigation via direct and indirect paths to the goal and allows the directionality of place cells to be assessed at each choice point. Place fields showed strong directional polarization characterized by vector fields that converged to sinks distributed throughout the environment. The distribution of these ‘convergence sinks’ (ConSinks) was centred near the goal location and the population vector field converged on the goal, providing a strong navigational signal. Changing the goal location led to movement of ConSinks and vector fields towards the new goal. The honeycomb maze allows independent assessment of spatial representation and spatial action in place cell activity and shows how the latter relates to the former. The results suggest that the hippocampus creates a vector-based model to support flexible navigation, allowing animals to select optimal paths to destinations from any location in the environment.

ZoonosisImpact of Rodent Outbreaks in Rice Paddies on Incidence of Rodent-borne Zoonosis in Human Populations

A study conducted in an area encircled by rice paddies on a rodent abundance, population, and flea vector index during normal and rodent outbreak periods revealed that the rodent populations of rice paddies were colonised in rice fields and are not migrated much to the residential areas even during the outbreak years. The predominance of Rattus rattus (94.2%) was recorded among the rodent species in residential premises, whereas in rice paddies, it was lesser bandicoot Bandicota bengalensis (98.9%). Among the structures in a residential area, bakeries were the most infested with pest rodents followed by grocery and vegetable stores. The recorded rat flea index of below 1 from the animals trapped in residential premises and no progression in fever and other ill health conditions among the residents even during field rodent outbreak years show no risk of zoonotic diseases like plague. Rodenticide poison offered through liquids has recorded high intake and control success over the market available ready-to-use bait cakes.

Hippocampal signals modify orbitofrontal representations to learn new paths

We often remember the consequences of past choices to adapt to changing circumstances. Recalling past events requires the hippocampus (HPC), and using stimuli to anticipate outcome values requires the orbitofrontal cortex (OFC).1-3 Spatial reversal tasks require both structures to navigate newly rewarded paths.4,5 Both HPC place6 and OFC value cells7,8 fire in phase with theta (4-12Hz) oscillations. Both structures are described as cognitive maps: HPC maps space9 and OFC maps task states.10 These similarities imply that OFC-HPC interactions are crucial for using memory to predict outcomes when circumstances change, but the mechanisms remain largely unknown. To investigate possible interactions, we simultaneously recorded ensembles in OFC and CA1 as rats learned spatial reversals in a plus maze. Striking interactions occurred only while rats learned their first reversal: CA1 population vectors predicted changes in OFC activity but not vice versa, OFC spikes phase locked to hippocampal theta oscillations, mixed pairs of CA1 and OFC neurons fired together within single theta cycles, and CA1 led OFC spikes by ∼30ms. After the new contingency became familiar, CA1 ensembles stably represented distinct spatial paths, whereas OFC ensembles developed more generalized goal arm representations in different paths to identical rewards. These frontotemporal interactions, engaged selectively when new task features inform decision-making, suggest a mechanism for linking novel episodes with expected outcomes, when HPC signals trigger "cognitive remapping" by OFC.11.

Action-driven remapping of hippocampal neuronal populations in jumping rats

The current dominant view of the hippocampus is that it is a navigation "device" guided by environmental inputs. Yet, a critical aspect of navigation is a sequence of planned, coordinated actions. We examined the role of action in the neuronal organization of the hippocampus by training rats to jump a gap on a linear track. Recording local field potentials and ensembles of single units in the hippocampus, we found that jumping produced a stereotypic behavior associated with consistent electrophysiological patterns, including phase reset of theta oscillations, predictable global firing-rate changes, and population vector shifts of hippocampal neurons. A subset of neurons ("jump cells") were systematically affected by the gap but only in one direction of travel. Novel place fields emerged and others were either boosted or attenuated by jumping, yet the theta spike phase versus animal position relationship remained unaltered. Thus, jumping involves an action plan for the animal to traverse the same route as without jumping, which is faithfully tracked by hippocampal neuronal activity.

Behavioural and neural responses of crabs show evidence for selective attention in predator avoidance

Selective attention, the ability to focus on a specific stimulus and suppress distractions, plays a fundamental role for animals in many contexts, such as mating, feeding, and predation. Within natural environments, animals are often confronted with multiple stimuli of potential importance. Such a situation significantly complicates the decision-making process and imposes conflicting information on neural systems. In the context of predation, selectively attending to one of multiple threats is one possible solution. However, how animals make such escape decisions is rarely studied. A previous field study on the fiddler crab, Gelasimus dampieri, provided evidence of selective attention in the context of escape decisions. To identify the underlying mechanisms that guide their escape decisions, we measured the crabs’ behavioural and neural responses to either a single, or two simultaneously approaching looming stimuli. The two stimuli were either identical or differed in contrast to represent different levels of threat certainty. Although our behavioural data provides some evidence that crabs perceive signals from both stimuli, we show that both the crabs and their looming-sensitive neurons almost exclusively respond to only one of two simultaneous threats. The crabs’ body orientation played an important role in their decision about which stimulus to run away from. When faced with two stimuli of differing contrasts, both neurons and crabs were much more likely to respond to the stimulus with the higher contrast. Our data provides evidence that the crabs’ looming-sensitive neurons play an important part in the mechanism that drives their selective attention in the context of predation. Our results support previous suggestions that the crabs’ escape direction is calculated downstream of their looming-sensitive neurons by means of a population vector of the looming sensitive neuronal ensemble.

New Research on the Intihuasi Cave, San Luis, Argentina: Implications for the Peopling of the Southern Cone of South America

In this report, we present a new 14C of 9627–9490 cal BC (8640 ± 30 BP) obtained at the Intihuasi Cave, San Luis, Argentina. The sample was obtained during fieldwork conducted as part of a new management plan for tourist use of the site. Intihuasi has played a central role in the history of archaeological investigations in South America. There, in 1951 González applied for the first time a systematic methodology for archaeological excavations in Argentina. Moreover, he complemented his field results with the obtainment of the first radiocarbon dates for the Southern Cone of South America. These achievements allowed him to build the first macroregional chronological sequence, which is still partially used. The new radiocarbon date presented in this article aims to reconsider the importance of the Intihuasi Cave for the discussion of the macroregional peopling of the Southern Cone of South America. We believe that the site ratifies the occurrence of an Andean population vector in the region.