Coherent Map Research Articles

Crystals of the brain.

When we find our way in the environment, we need to integrate information about location, direction and distance into a coherent map-like representation. Our work over the last 10 years has suggested that the medial entorhinal cortex plays a central role in this process. A key component of the entorhinal network for spatial mapping is the grid cell, which we discovered, together with our colleagues, in 2005. Grid cells fire only when animals move through specific, regularly spaced positions. Their active firing positions form a hexagonal pattern that spans, for each cell, the entire local space available to the animal (Fig 1). The periodic pattern is reminiscent of the cross-points of graphic paper but the repeating units are equilateral triangles, not squares. Grid cells interact with other specialized cell types, such as head-direction cells and border cells. Head-direction cells signal orientation whereas border cells fire only near the edge of the local environment (Fig 2). Together, these entorhinal cells establish a coherent generic map of local space that is maintained across environments, independently of the animal's speed and direction and independently of the identity of the particular landmarks of the place. Figure 1 Entorhinal grid cell Figure 2 Border cells, grid cells and head direction cells are the elements of a metric representation of local space and are likely to be used when animals navigate through the environment »Grid cells have attracted attention because the crystal-like structure underlying their firing fields is not, like in sensory systems, imported from the outside world, but is created within the brain itself.« “One synapse” downstream, in the hippocampus, the map is associated with specific features and experiences, forming individualized maps that are stored in the neural networks of this brain region. Studies of grid cells may thus provide access to some of the basic computational operations of cortical circuits. In this Perspective, we shall review the work that led to the discovery of grid cells and the entorhinal spatial map, concluding with a brief look to the future.

The Ideological “Coherence” of the Brazilian Party System, 1990-2009

This paper contributes to the debate about the ideological coherence of the Brazilian party system. Using discriminant function analysis of 20 years of surveys of Brazilian legislators, we find that the party system now exhibits relatively little coherence. Though the Worker's Party (PT) is clearly distinct, no clear ideological differences exist between the placement of the system's three other main parties. Moreover, the spatial distance between the PT and the other parties is diminishing over time. Given the importance of a coherent ideological map to any consolidated party system, we question the notion that the Brazilian party system has gradually consolidated. Indeed, our results suggest the opposite: in recent years the Brazilian party system has become relatively more “inchoate.”

Stylized ambient displays of digital media collections

The falling cost of digital cameras and camcorders has encouraged the creation of massive collections of personal digital media. However, once captured, this media is infrequently accessed and often lies dormant on users' PCs. We present a system to breathe life into home digital media collections, drawing upon artistic stylization to create a “Digital Ambient Display” that automatically selects, stylizes and transitions between digital contents in a semantically meaningful sequence. We present a novel algorithm based on multi-label graph cut for segmenting video into temporally coherent region maps. These maps are used to both stylize video into cartoons and paintings, and measure visual similarity between frames for smooth sequence transitions. The system automatically structures the media collection into a hierarchical representation based on visual content and semantics. Graph optimization is applied to adaptively sequence content for display in a coarse-to-fine manner, driven by user attention level (detected in real-time by a webcam). Our system is deployed on embedded hardware in the form of a compact digital photo frame. We demonstrate coherent segmentation and stylization over a variety of home videos and photos. We evaluate our media sequencing algorithm via a small-scale user study, indicating that our adaptive display conveys a more compelling media consumption experience than simple linear “slide-shows”.

Central oscillators in a patient with neuropathic tremor: Evidence from intraoperative local field potential recordings

Present pathophysiological concepts of neuropathic tremor assume mistimed and defective afferent input resulting in deregulation of cerebello-thalamo-cortical motor networks. Here, we provide direct evidence of central tremor processing in a 76-year-old female who underwent bilateral deep brain stimulation of the ventral intermedial nucleus of the thalamus (Vim-DBS) because of neuropathic tremor associated with IgM paraproteinemia. Electrophysiological recordings of EEG and EMG were performed in three perioperative sessions: (1) preoperatively, (2) intraoperatively, and (3) 4 days after surgery in both rest and postural tremor conditions. Tremor-related synchronization (coherence) between motor cortex (M1) and muscles (M. extensor digitorum, M. flexor digitorum) was assessed, and additional intraoperative local field potential (LFP) recordings from Vim allowed comprehensive coherence mapping in thalamo-cortico-muscular networks. Directionality of information flow was determined by directed transfer function (DTF) and phase analyses. Stimulation effects on tremor and corticomuscular coherence were assessed and the patient was followed for 12 months on clinical outcome measures (Tremor Rating Scale, CADET-Score). Vim-DBS reduced tremor (59%) and improved motor functionality in daily activities (31%, CADET-A) after 12 months. Intraoperative recordings demonstrated significant coherence in the tremor frequency (4 Hz) between M1 and contralateral muscle, Vim and ipsilateral M1, Vim and contralateral muscle, but not between Vim and contralateral M1. Information flow was directed from M1 to Vim and bidirectional between M1 and muscle and between Vim and muscle, respectively. Corticomuscular coherence at tremor frequency was completely suppressed by Vim-DBS. Our case study demonstrates central oscillators underlying neuropathic tremor and implies a strong pathophysiological rationale for Vim-DBS.

Concept Development and Transfer in Context‐Based Science Education

‘Context‐based courses’ are increasingly used in an address to the major challenges that science education currently faces: lack of clear purpose, content overload, incoherent learning by students, lack of relevance to students, and lack of transfer of learning to new contexts. In this paper, four criteria for the design of context‐based courses that would be successful in meeting these challenges are rehearsed. It is concluded that only a model based on ‘context as social circumstances’ would meet the four criteria for success. From this, the notion of concept development is presented based on the idea of the production of coherent mental maps. The notion of transfer is discussed in terms of how such mental maps may be useful for understanding other contexts. The definitions of concept development and transfer give a clearer view of how exemplars of existing context‐based approaches may be analysed to show their degree of facilitation of worthwhile science education. Research questions to be addressed in such analyses are presented.

Fine-scale detection of population-specific linkage disequilibrium using haplotype entropy in the human genome

BackgroundThe creation of a coherent genomic map of recent selection is one of the greatest challenges towards a better understanding of human evolution and the identification of functional genetic variants. Several methods have been proposed to detect linkage disequilibrium (LD), which is indicative of natural selection, from genome-wide profiles of common genetic variations but are designed for large regions.ResultsTo find population-specific LD within small regions, we have devised an entropy-based method that utilizes differences in haplotype frequency between populations. The method has the advantages of incorporating multilocus association, conciliation with low allele frequencies, and independence from allele polarity, which are ideal for short haplotype analysis. The comparison of HapMap SNPs data from African and Caucasian populations with a median resolution size of ~23 kb gave us novel candidates as well as known selection targets. Enrichment analysis for the yielded genes showed associations with diverse diseases such as cardiovascular, immunological, neurological, and skeletal and muscular diseases. A possible scenario for a selective force is discussed. In addition, we have developed a web interface (ENIGMA, available at http://gibk21.bse.kyutech.ac.jp/ENIGMA/index.html), which allows researchers to query their regions of interest for population-specific LD.ConclusionThe haplotype entropy method is powerful for detecting population-specific LD embedded in short regions and should contribute to further studies aiming to decipher the evolutionary histories of modern humans.

Mapping multiple photonic qubits into and out of one solid-state atomic ensemble

The future challenge of quantum communication is scalable quantum networks, which require coherent and reversible mapping of photonic qubits onto atomic systems (quantum memories). A crucial requirement for realistic networks is the ability to efficiently store multiple qubits in one quantum memory. In this study, we show a coherent and reversible mapping of 64 optical modes at the single-photon level in the time domain onto one solid-state ensemble of rare-earth ions. Our light-matter interface is based on a high-bandwidth (100 MHz) atomic frequency comb, with a predetermined storage time of ≳ 1 μs. We can then encode many qubits in short (<10 ns) temporal modes (time-bin qubits). We show the good coherence of mapping by simultaneously storing and analysing multiple time-bin qubits.

The Ecology of Homelessness

This article proposes an ecological model of homelessness drawn from a broad review of the research and practice literature. The spectrum of biopsychosocial risks associated with pathways into homelessness is reviewed, followed by examination of social and individual consequences resulting from periods of homelessness. The temporal dimensions of homelessness, including “first-time,” “episodic,” and “chronic,” are defined and discussed along with the continuum of living arrangements experienced by homeless individuals and families. These constituent domains of the ecology of homelessness are presented in a conceptual map depicting the relationships and interactions among the parts of the model. The intention is to provide a coherent and cogent map to encourage comprehensive integrated efforts as individuals, agencies, and communities strive to prevent and resolve homelessness.

Power halo and magnetic shadow in a solar quiet region observed in the Hαline

<i>Context. <i/>We investigate the oscillatory behavior of the quiet solar chromosphere and its discrete components in terms of oscillation properties, i.e. network and internetwork. For this purpose, we use a time series of high resolution filtergrams at five wavelengths along the profile, obtained by the Dutch Open Telescope.<i>Aims. <i/>We aim to gain insight on the distribution of power in different period bands and its variation between network and internetwork. Our spectral resolution provides information on the vertical distribution of power, since the line has both photospheric and chromospheric components. We investigate the effect of mottles on chromospheric oscillations, since they are the most prominent feature of the chromosphere and outline inclined magnetic fields.<i>Methods. <i/>We use wavelet and phase difference analyses of intensities and Doppler signals. Two-dimensional power maps in the 3, 5 and 7 min period bands as well as coherence and phase difference maps were constructed.<i>Results. <i/>At photospheric heights, where the <i>±<i/> 0.7 Å wing is formed, the 3 and 5 min power is enhanced around the network, and forms power halos. Higher in the chromosphere these areas are replaced by magnetic shadows, i.e. places of power suppression. Interestingly, the power maps show a filamentary structure in the network which correlates very well with mottles. These areas show positive phase differences at the 3 min period band. At the 5 min and 7 min period bands both positive and negative phase differences are obtained with an increased number of pixels with high coherence, indicating the existence of both upward and downward propagating waves.<i>Conclusions. <i/>We attribute our findings to the interaction between acoustic oscillations and the magnetic fields that constitute the magnetic network. The network flux tubes diverge at chromospheric levels and obtain a significant horizontal component, which is betrayed by the presence of mottles. The variation of power reveals the discrete role of the magnetic field at different heights, which guides or suppresses the oscillations, depending on its inclination. Spectral resolution in provides useful information on the coupling between the acoustic sub-canopy atmosphere and the magnetized chromosphere.

Molecular heat pump for rotational states

In this work, we investigate the theory for three different unidirectional population-transfer schemes in trapped multilevel systems which can be utilized to cool molecular ions. The approach we use exploits the laser-induced coupling between the internal and motional degrees of freedom so that the internal state of a molecule can be mapped onto the motion of that molecule in an external trapping potential. By sympathetically cooling the translational motion back into its ground state, the mapping process can be employed as part of a cooling scheme for molecular rotational levels. This step is achieved through a common mode involving a laser-cooled atom trapped alongside the molecule. For the coherent mapping, we will focus on adiabatic passage techniques which may be expected to provide robust and efficient population transfers. By applying far-detuned chirped adiabatic rapid passage pulses, we are able to achieve an efficiency of better than $98%$ for realistic parameters and including spontaneous emission. Even though our main focus is on cooling molecular states, the analysis of the different adiabatic methods has general features which can be applied to atomic systems.

Mixture model for the segmentation of the InSAR coherence map

In this work, we classify the interferometric SAR (InSAR) coherence map, computed with the second kind statistics (Abdelfattah and Nicolas, 2006a), into three classes using Bayes’ theorem. The segmentation procedure is performed using a mixture modelling of the coherence map. The multimodal density of the mixture comprises three component functions characterizing different land surface categories (lake, bare soil, urban …). This work is an amelioration version of that published by the authors in (Abdelfattah and Nicolas, 2007, 2006b). We test the performance of the proposed mixture model on three different datasets. The results of this study could be used as a supervised learning step for an automatic land cover classification algorithm. This new method classifying the image considering the corresponding InSAR coherence map is particularly powerful for the detection of layover and shadow regions.

Interpersonal dynamics and multidisciplinary teamwork

SummaryAnalysing interpersonal dynamics is an approach through which the multidisciplinary team can develop a shared understanding of their patients. This empirically based method provides an insight into repeated patterns of dysfunctional behaviour, which not only have been evident in the past, but are currently having an impact on the patient's relationships with caring staff. The technique is accessible to any team member with only minimal training required. It provides the team with a coherent map of the patient's relationship patterns that underpins the formulation of an effective strategy for care. The multidisciplinary team is then able to work towards shared goals, supporting all members in their provision of effective interventions within the full range of therapeutic modalities. The approach promotes positive staff–patient interactions and provides an additional dimension to the assessment and management of risk.

Independent Coherence Mapping in Magnetoencephalography and its Application to Theory of Mind Analysis

Independent Coherence Mapping in Magnetoencephalography and its Application to Theory of Mind Analysis

Investigating readers’ mental maps of references in an online system

Referential identification and resolution are considered the keys to help readers grasp the main idea of a text and solve lexical ambiguities. The goal of this study is to design a computer system for helping college students who learn English as a Foreign Language (EFL) develop mental maps of referential identification and resolution in reading. Four modules, Natural Language Processing (NLP), User Interface, Recording, and Feedback Tool, are implemented in the system. Results of this study showed that the more-proficient EFL readers were able to identify and resolve most of the references to form a coherent mental map from different parts of a text. The less-proficient readers commonly resolved references by relying on grammatical rules instead of semantic contextual clues. They often referred references to incorrect objects. To overcome the difficulties in figuring out the relationship between two words, the less-proficient readers usually asked for more feedbacks. As students progressed in reading, they requested fewer feedbacks in the online system. Some recommendations for future studies are discussed.

Gearbox Condition Estimation Using Cyclo-Stationary Properties of Vibration Signal

The paper explores the cyclo-stationary properties of vibration signals for estimation of gearbox condition. The advantage of such approach may be clearly seen especially for so called multi-faults problem, i.e. for more than one faults that occurred in the system. In complex mechanical systems like multistage gearboxes, such situation may be often seen. Although this approach becomes more and more popular, it has been noticed that there is difficult to find examples highlighting its potential, especially for real industrial situations. In order to fill partially the gap, the paper deals with the multi fault detection in complex mechanical systems like multi-stage gearboxes: fixed axis and planetary. It has been discussed that during the operation in such machines many faults may appear simultaneously and the classical method like envelope analysis is difficult to use. The paper presents the use of cyclo-stationary properties of signals to identify and characterize sources of modulation. From Spectral Correlation Density Map or more precisely Spectral Coherence Map have been observed the number of sources with different properties of modulation. It is shown that the number of harmonics is important for a kind of fault extraction and interpretation. This approach has been applied to two, three and five stage gearboxes used in mining industry. Vibration signals received in industrial environment during normal operation of objects are considered. It has been also proposed the simple diagnostic feature to estimate the changes of condition with application to a planetary stage in a 5-stage gearbox.

Remote sensing data types and techniques for lahar path detection: A case study at Mt Ruapehu, New Zealand

Mt Ruapehu is New Zealand's most active onshore volcano. In 2007, the volcano produced a large lahar following a break-out from the summit Crater Lake. Here, satellite and airborne remote sensing and image processing is used to extract the path of the lahar using ASTER and SPOT5 visible and near infra-red imagery, ALOS-PALSAR L-band synthetic aperture RADAR data, and airborne LiDAR. The results obtained from each of these datasets were compared to the lahar deposit manually digitized from aerial photography. SPOT5 imagery produced the most accurate map of the lahar deposit (77% correct), even though these data were acquired a year after the event. This is attributed to the spatial resolution of the data. The ALOS-PALSAR coherence mapping calculated from images acquired 2 months before and nine months after the lahar was not as accurate as that obtained using the optical imagery (43% correct), but this was still considered an important tool for acquiring data during cloudy periods. LiDAR topographic data, collected to constrain geomorphic changes caused by the lahar, was the least accurate in terms of mapping the lahar path (28% correct). No single technique was deemed to be the most accurate under all circumstances, and a combination of data types would produce the best results. By combining the satellite and LiDAR data, it was possible to accurately classify 92% of the lahar path.

Epicompletion in Frames with Skeletal Maps, III: When Maps are Closed

In previous work it was shown that there is an epireflection ψ of the category of all compact normal, joinfit frames, with skeletal maps, in the full subcategory of frames which are also strongly projectable, and that ψ restricts to the epicompletion e, which is the absolute reflection on compact regular frames. In the first part of this paper it is shown that ψ is a monoreflection and that the reflection map is, in fact, closed. Restricted to coherent frames and maps, ψ A can then be characterized as the least strongly projectable, coherent, normal, joinfit frame in which A can be embedded as a closed, coherent, and skeletal subframe. The second part discusses the role of the nucleus d in this context. On algebraic frames with coherent skeletal maps d becomes an epireflection. Further, it is shown that e = d · ψ epireflects the category of coherent, normal, joinfit frames, with coherent skeletal maps, in the subcategory of those frames which are also regular and strongly projectable, which are epicomplete. The action of e is not monoreflective.

Mapping and monitoring carbon stocks with satellite observations: a comparison of methods

Mapping and monitoring carbon stocks in forested regions of the world, particularly the tropics, has attracted a great deal of attention in recent years as deforestation and forest degradation account for up to 30% of anthropogenic carbon emissions, and are now included in climate change negotiations. We review the potential for satellites to measure carbon stocks, specifically aboveground biomass (AGB), and provide an overview of a range of approaches that have been developed and used to map AGB across a diverse set of conditions and geographic areas. We provide a summary of types of remote sensing measurements relevant to mapping AGB, and assess the relative merits and limitations of each. We then provide an overview of traditional techniques of mapping AGB based on ascribing field measurements to vegetation or land cover type classes, and describe the merits and limitations of those relative to recent data mining algorithms used in the context of an approach based on direct utilization of remote sensing measurements, whether optical or lidar reflectance, or radar backscatter. We conclude that while satellite remote sensing has often been discounted as inadequate for the task, attempts to map AGB without satellite imagery are insufficient. Moreover, the direct remote sensing approach provided more coherent maps of AGB relative to traditional approaches. We demonstrate this with a case study focused on continental Africa and discuss the work in the context of reducing uncertainty for carbon monitoring and markets.

Accounting Data and Value: The Basic Results*

Subsequent to Feltham and Ohlson 1995 and Ohlson 1995, the accounting literature has published a large numbers of papers on accounting data and value.1 A review of this literature reveals that many themes and insights recur across the papers. With the advantage of hindsight, the repetitions seem inefficient. A student who takes a stab at familiarizing herself with subject matter naturally tends to view such a state of affairs as less than ideal. Questions like “What is it that I really need to understand?” or “Taken in its totality, what ideas and results make the literature tick?” arise. This paper addresses the essence of such questions. It states the central results as eight simple formal propositions. Because all the propositions are freestanding, they can, at least in principle, be internalized independently of each other. But the sequencing is in fact relevant because it introduces step-by-step increasingly sophisticated concepts. The concepts build upon each other; the propositions’ analytical simplicity should, therefore, not be taken as a sign that they are conceptually simplistic. Much discussion follows the propositions to spell out their broader significance. And the paper approaches this task always maintaining the texture of accounting: the central variables are earnings, book values, and dividends. The paper does not digress on proofs and finer analytical points. These aspects are of little interest, which is another way of saying that the paper focuses squarely on analytical constructs/representations and how these fit together. Nor does this paper elaborate on the extent to which the literature has already dealt with the results or insights. There is no question that most, if not all, results have had some kind of presence and thus lack novelty. That said, such cataloguing and related discussion would have been long and tedious without facilitating a better understanding of the insights I wish to convey. Aside from trying to systemize the literature, and thereby making it more accessible to the average reader, the paper also has a more ambitious objective. It goes to the heart of subject matter: the exposition should give the reader the sense that all pieces and insights interrelate logically and conceptually. In other words, the task at hand is to go beyond a listing of useful results (though this should hopefully be the case, too), and instead give a sense of how the various pieces coalesce into a whole. The development of such a coherent mental map allows the reader to think of the broad literature in an integrated fashion, rather than as consisting of loosely connected, or even competing, models that primarily differ in their empirical

Coherence analysis between respiration and heart rate variability using continuous wavelet transform

The continuous wavelet transform (CWT) is specifically efficient in the analysis of transient and non-stationary signals. As such, it has become a powerful candidate for time-frequency analysis of cardiovascular variability. CWT has already been established as a valid tool for the analysis of single cardiovascular signals, providing additional insights into the autonomous nervous system (ANS) activity and its control mechanism. Intercorrelation between cardiovascular signals elucidates the function of ANS central control and the peripheral reflex mechanisms. Wavelet transform coherence (WTC) can provide insight into the transient linear order of the regulatory mechanisms, via the computation of time-frequency maps of the time-variant coherence. This paper presents a framework for applying WTC for quantitative analysis of coherence in cardiovascular variability research. Computer simulations were performed to estimate the accuracy of the WTC estimates and a method for determining the coherence threshold for specific frequency band was developed and evaluated. Finally, we demonstrated, in two representative situations, the dynamic behaviour of respiration sinus arrhythmia through the analysis of the WTC between heart rate and respiration signals. This emphasizes that CWT and its application to WTC is a useful tool for dynamic analysis of cardiovascular variability.