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Magnetic Field Strength Encoded Handheld Magnetic Particle Imaging System With Multiwaveform Excitation

IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT 2024年 73卷 1页

作者： Zhang, Bo Zhang, Haoran Gao, Pengli Hui, Hui An, Yu Tian, Jie Beihang Univ Sch Engn Med Beijing 100191 Peoples R China Beihang Univ Sch Biol Sci & Med Engn Beijing 100191 Peoples R China Beihang Univ Minist Ind & Informat Technol China Key Lab Big Data Based Precis Med Beijing 100191 Peoples R China Natl Key Lab Kidney Dis Beijing 100853 Peoples R China Beijing Key Lab Mol Imaging Inst Automat CAS Key Lab Mol Imaging Beijing 100190 Peoples R China

Magnetic particle imaging (MPI) is an innovative medical imaging modality with tremendous potential for various clinical applications. The handheld MPI device, due to its high biosafety and portability, holds promise for use in intraoperative diagnosis and other clinical settings. The handheld MPI system has all its hardware components located on one side of the imaged object, enabling convenient mobile detection. However, this single-sided construction leads to a reduced magnetic field gradient of the selection field, resulting in a compromised imaging field of view (FOV) and resolution. To address these challenges, this study proposes a handheld MPI system that utilizes excitation field intensity encoding. By gradually increasing the calibrated excitation field, spatial encoding is achieved throughout the FOV. To improve the imaging resolution of the system, three different excitation waveforms are applied to the excitation coil to expand the available harmonic signals. In addition, a bidirectional adjustable external compensation strategy is introduced to achieve more precise direct feedthrough suppression, restoring the baseband signal. Experimental results demonstrate that the proposed handheld MPI achieves a spatial resolution of 1 mm within a depth range of 30 mm while maintaining imaging FOV, resolution, and detection sensitivity of 50-ng Fe, laying a foundation for future clinical applications.

关键词： Compensation strategy excitation waveform handheld MPI magnetic particle imaging (MPI) spatial coding

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Conjoint generalized and trajectory-specific coding of task structure by prefrontal neurons

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CELL REPORTS 2025年第3期44卷 115420页

作者： Muysers, Hannah Bartos, Marlene Sauer, Jonas-Frederic Albert Ludwigs Univ Inst Physiol 1 Med Fac D-79104 Freiburg Germany Albert Ludwigs Univ Fac Biol D-79104 Freiburg Germany Saarland Univ Inst Physiol Ctr Integrat Physiol & Mol Med D-66421 Homburg Germany

Neurons in the medial prefrontal cortex (mPFC) are spatially tuned. Trajectory-specific firing with distinct spatial tuning on different paths to reward sites as well as generalized spatial tuning with similar responses on separate trajectories have been described. However, it is unclear whether such distinct populations contribute differently to the encoding of task space. Here, we find coexisting populations of neurons with trajectory-specific and generalized tuning profiles in an olfaction-guided spatial memory task in mice. Neurons with generalized representation show stable spatial tuning within and across days, allow accurate predictions of the animal's position, and preferentially emerge upon task learning. In contrast, cells with trajectory-specific spatial tuning display dynamically changing tuning functions, are less informative about the current position, and can be identified at a larger proportion early in task learning. These results highlight a role for neurons with generalized tuning in the efficient and stable representation of task space.

关键词： medial prefrontal cortex generalized representation spatial coding miniscope calcium imaging space representation

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Egocentric cues influence the allocentric spatial memory of object configurations for memory-guided actions

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JOURNAL OF NEUROPHYSIOLOGY 2023年第5期130卷 1142-1149页

作者： Forster, Pierre-Pascal Fiehler, Katja Karimpur, Harun Justus Liebig Univ Giessen Expt Psychol Giessen Germany Univ Marburg Ctr Mind Brain & Behav CMBB Marburg Germany Justus Liebig Univ Giessen Giessen Germany

Allocentric and egocentric reference frames are used to code the spatial position of action targets in reference to objects in the environment, i.e., relative to landmarks (allocentric), or the observer (egocentric). Previous research investigated reference frames in isolation, for example, by shifting landmarks relative to the target and asking participants to reach to the remembered target location. Systematic reaching errors were found in the direction of the landmark shift and used as a proxy for allocentric spatial coding. Here, we examined the interaction of both allocentric and egocentric reference frames by shifting the landmarks as well as the observer. We asked participants to encode a three-dimensional configuration of balls and to reproduce this configuration from memory after a short delay followed by a landmark or an observer shift. We also manipulated the number of landmarks to test its effect on the use of allocentric and egocentric reference frames. We found that participants were less accurate when reproducing the configuration of balls after an observer shift, which was reflected in larger configurational errors. In addition, an increase in the number of landmarks led to a stronger reliance on allocentric cues and a weaker contribution of egocentric cues. In sum, our results highlight the important role of egocentric cues for allocentric spatial coding in the context of memory-guided actions.

关键词： reference frames spatial coding spatial representations virtual reality visual working memory

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Sparse Layered MIMO With Iterative Detection

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IEEE TRANSACTIONS ON COMMUNICATIONS 2022年第3期70卷 2042-2056页

作者： Dinan, Mohamad H. Perovic, Nemanja Stefan Flanagan, Mark F. Univ Coll Dublin Sch Elect & Elect Engn Dublin D04 V1W8 4 Ireland

In this paper, we propose a novel transmission scheme, called sparse layered MIMO (SL-MIMO), that combines non-orthogonal transmission and singular value decomposition (SVD) precoding. Non-orthogonality in SL-MIMO allows re-using of the eigen-channels which improves the spectral efficiency and error rate performance of the system through enhancing the coding gain and diversity gain. We also present a low-complexity message-passing (MP) detector for the proposed SL-MIMO system which performs quite close to maximum likelihood (ML). The joint moment generating function (MGF) of the ordered eigenvalues is calculated and used to derive a closed-form upper bound on the average word error probability (AWEP) of the SL-MIMO system, and this derived expression is then used to analyze the diversity gain of the system. We use our analytical results to design sub-optimal codebooks to minimize the error rate of the SL-MIMO system. Simulation results in 4 x 4 and 6 x 6 multiple-input multiple-output (MIMO) systems with 4-ary, 16-ary, and 64-ary constellations show that our proposed SL-MIMO scheme outperforms competing approaches such as X- and Y-codes in terms of system error rate performance. SL-MIMO has 5.6 dB advantage compared to X-codes and 4.7 dB advantage compared to Y-codes in 6 x 6 MIMO system with a 64-ary constellation.

关键词： MIMO communication Precoding Eigenvalues and eigenfunctions Diversity methods Complexity theory Codes Sparse matrices Multiple-input multiple-output (MIMO) precoding code-domain non-orthogonal transmission spatial coding joint moment generating function (MGF) of ordered eigenvalues

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Grid codes vs. multi-scale, multi-field place codes for space

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FRONTIERS IN COMPUTATIONAL NEUROSCIENCE 2024年 18卷 1276292页

作者： Dietrich, Robin Waniek, Nicolai Stemmler, Martin Knoll, Alois Tech Univ Munich Sch Computat Informat & Technol Munich Germany Norwegian Univ Sci & Technol Kavli Inst Syst Neurosci Trondheim Norway Norwegian Univ Sci & Technol Dept Math Sci Trondheim Norway Ludwig Maximilians Univ Munchen Bernstein Ctr Computat Neurosci Munich Germany

Introduction Recent work on bats flying over long distances has revealed that single hippocampal cells have multiple place fields of different sizes. At the network level, a multi-scale, multi-field place cell code outperforms classical single-scale, single-field place codes, yet the performance boundaries of such a code remain an open question. In particular, it is unknown how general multi-field codes compare to a highly regular grid code, in which cells form distinct modules with different *** In this work, we address the coding properties of theoretical spatial coding models with rigorous analyses of comprehensive simulations. Starting from a multi-scale, multi-field network, we performed evolutionary optimization. The resulting multi-field networks sometimes retained the multi-scale property at the single-cell level but most often converged to a single scale, with all place fields in a given cell having the same size. We compared the results against a single-scale single-field code and a one-dimensional grid code, focusing on two main characteristics: the performance of the code itself and the dynamics of the network generating *** Our simulation experiments revealed that, under normal conditions, a regular grid code outperforms all other codes with respect to decoding accuracy, achieving a given precision with fewer neurons and fields. In contrast, multi-field codes are more robust against noise and lesions, such as random drop-out of neurons, given that the significantly higher number of fields provides redundancy. Contrary to our expectations, the network dynamics of all models, from the original multi-scale models before optimization to the multi-field models that resulted from optimization, did not maintain activity bumps at their original locations when a position-specific external input was *** Optimized multi-field codes appear to strike a compromise between a place code and a grid code that reflects a trade-off between

关键词： place cells grid cells continuous attractor networks spatial coding multiple scales hippocampus localization evolutionary optimization

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Reconciling the object and spatial processing views of the perirhinal cortex through task-relevant unitization

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HIPPOCAMPUS 2021年第7期31卷 737-755页

作者： Fiorilli, Julien Bos, Jeroen J. Grande, Xenia Lim, Judith Duezel, Emrah Pennartz, Cyriel M. A. Univ Amsterdam SILS Ctr Neurosci Cognit & Syst Neurosci Grp Postbus 94246 NL-1090 GE Amsterdam Netherlands Univ Amsterdam Res Prior Area Brain & Cognit Amsterdam Netherlands Radboud Univ Nijmegen Donders Inst Brain Cognit & Behav Nijmegen Netherlands Radboud Univ Nijmegen Med Ctr Nijmegen Netherlands Otto von Guericke Univ Inst Cognit Neurol & Dementia Res Magdeburg Germany German Ctr Neurodegenerat Dis Magdeburg Germany UCL Inst Cognit Neurosci London England

The perirhinal cortex is situated on the border between sensory association cortex and the hippocampal formation. It serves an important function as a transition area between the sensory neocortex and the medial temporal lobe. While the perirhinal cortex has traditionally been associated with object coding and the "what" pathway of the temporal lobe, current evidence suggests a broader function of the perirhinal cortex in solving feature ambiguity and processing complex stimuli. Besides fulfilling functions in object coding, recent neurophysiological findings in freely moving rodents indicate that the perirhinal cortex also contributes to spatial and contextual processing beyond individual sensory modalities. Here, we address how these two opposing views on perirhinal cortex-the object-centered and spatial-contextual processing hypotheses-may be reconciled. The perirhinal cortex is consistently recruited when different features can be merged perceptually or conceptually into a single entity. Features that are unitized in these entities include object information from multiple sensory domains, reward associations, semantic features and spatial/contextual associations. We propose that the same perirhinal network circuits can be flexibly deployed for multiple cognitive functions, such that the perirhinal cortex performs similar unitization operations on different types of information, depending on behavioral demands and ranging from the object-related domain to spatial, contextual and semantic information.

关键词： contextual processing hippocampus multisensory integration perirhinal cortex spatial coding

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Distinct spatial maps and multiple object codes in the lateral entorhinal cortex

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NEURON 2023年第19期111卷 3068-+页

作者： Huang, Xu Schlesiger, Magdalene Isabell Barriuso-Ortega, Isabel Leibold, Christian MacLaren, Duncan Archibald Allan Bieber, Nina Monyer, Hannah Heidelberg Univ Med Fac Dept Clin Neurobiol Neuenheimer Feld 280 D-69120 Heidelberg Germany German Canc Res Ctr Neuenheimer Feld 280 D-69120 Heidelberg Germany Univ Freiburg Inst Biol 3 D-79104 Freiburg Germany Univ Freiburg Bernstein Ctr Freiburg D-79104 Freiburg Germany Univ Freiburg Brainlinks Braintools D-79110 Freiburg Germany

The lateral entorhinal cortex (LEC) is a major cortical input area to the hippocampus, and it is crucial for asso-ciative object-place-context memories. An unresolved question is whether these associations are performed exclusively in the hippocampus or also upstream of it. Anatomical evidence suggests that the LEC processes both object and spatial information. We describe here a gradient of spatial selectivity along the antero-posterior axis of the LEC. We demonstrate that the LEC generates distinct spatial maps for different contexts that are independent of object coding and vice versa, thus providing evidence for pure spatial and pure object codes upstream of the hippocampus. While space and object coding occur by and large separately in the LEC, we identified neurons that encode for space and objects conjunctively. Together, these findings point to a scenario in which the LEC sustains both distinct space and object coding and associative space-object coding.

关键词： lateral entorhinal cortex spatial coding object coding hippocampus place cells

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Grid cells in rats deprived of geometric experience during development

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PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 2023年第41期120卷 e2310820120-e2310820120页

作者： Ulsaker-Janke, Ingvild Waaga, Torgeir Waaga, Tanja Moser, Edvard I. Moser, May - Britt Norwegian Univ Sci & Technol Kavli Inst Syst Neurosci N-7491 Trondheim Norway Norwegian Univ Sci & Technol Ctr Algorithms Cortex N-7491 Trondheim Norway Norwegian Univ Sci & Technol St Olavs Univ Hosp Trondheim Sleep & Chronobiol Res Grp N-7491 Trondheim Norway Friedrich Miescher Inst Biomed Res Luthi Grp CH-4058 Basel Switzerland

The medial entorhinal cortex (MEC) is part of the brain's network for dynamic representation of location. The most abundant class of neurons in this circuit is the grid cell, characterized by its periodic, hexagonally patterned firing fields. While in developing animals some MEC cell types express adult-like firing patterns already on the first exposure to an open spatial environment, only days after eye opening, grid cells mature more slowly, over a 1-to-2-wk period after the animals leave their nest. Whether the later emergence of a periodic grid pattern reflects a need for experience with spatial environments has not been determined. We here show that grid-like firing patterns continue to appear during exploration of open square environments in rats that are raised for the first months of their life in opaque spherical environments, in the absence of stable reference boundaries to guide spatial orientation. While strictly periodic firing fields were initially absent in these animals, clear grid patterns developed after only a few trials of training. In rats that were tested in the same open environment but raised for the first months of life in opaque cubes, with sharp vertical boundaries, grid-like firing was from the beginning indistinguishable from that of nondeprived control animals growing up in large enriched cages. Thus, although a minimum of experience with peripheral geometric boundaries is required for expression of regular grid patterns in a new environment, the effect of restricted spatial experience is overcome with short training, consistent with a preconfigured experience-independent basis for the grid pattern.

关键词： hippocampus entorhinal cortex spatial coding development

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Single pixel imaging and its applications

Single pixel imaging and its applications

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Optical Technology and Measurement for Industrial Applications Conference

作者： Nitta, Kouichi Kobe Univ Grad Sch Grad Syst Informat Rokkodai 1-1 Kobe Hyogo 6578501 Japan

ISBN: (数字)9781510647237

ISBN: (纸本)9781510647237;9781510647220

Single pixel imaging (SPI) is considered to be a promised technique in computational imaging because of some advantageous features and suitability for signal restoration with compressive sensing, deep learning, and so on. In this presentation, the principle of SPI is explained. In the SPI, two dimensional spatial modulation for optical signals is an important operations. A procedure for renewal of the modulation has been proposed. This procedure with spatial pattern shift is suitable for a some specific implementation based on SPI. Especially, it is useful for imaging of a target moving at a constant velocity. This procedure is introduced and usefulness of it is discussed.

关键词： Single pixel imaging Computational imaging spatial coding Image reconstruction Structured illumination

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NEUROSCIENCE LETTERS 2022年第0期790卷 000-000页

作者： Zhang, Yi Fan Mameri, Samir Xie, Ting Sadoun, Amirouche Univ Toulouse 3 CNRS UMR 5549 Toulouse France Univ Paul Sabatier Univ Toulouse 3 Ctr Rech Cerveau & Cognit Toulouse France Univ Bordj Bou Arreridj El Anceur Algeria Univ Bejaia Lab Theoret Phys LPT Bejaia Algeria INSERM U1037 Ctr Rech Cancerol Toulouse CRCT F-31037 Toulouse France Univ Paul Sabatier III F-31400 Toulouse France CHU Purpan CNRS UMR 5549 Cerveau & Cognit Pavillon BaudotBP 25202 F-31052 Toulouse 03 France Theaterstr 26 Gottingen Germany

Neuroimaging studies have shown that brain activity is variable and changes according to stimuli and the environmental context, reflecting brain coding or information representations at different processing levels. However, little is known about activity organization that reflects coding strategies. Here, we explored and compared two different coding approaches, spatial via cross-correlation and intensity-based coding using mutual information. Using two fMRI datasets and different seeds, we searched for the spatial and intensity-based sim-ilarities with the seeds in brain activity. Our results showed that, apart from the seed regions, significant regions detected by intensity-based similarity analysis differ completely from those found using cross-correlation. These findings may indicate that information shared through spatial coding differs from that transmitted via non-spatial coding processes. Our results suggest that brain coding is organized in several different ways to opti-mize information processing.

关键词： spatial cross-correlation Intensity coding Mutual information Neuronal code spatial coding

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