A new view of hemineglect based on the response properties of parietal neurones

Lesion studies of the parietal cortex have led to a wide range of conclusions regarding the coordinate reference frame in which hemineglect is expressed. A model of spatial representation in the parietal cortex has recently been developed in which the position of an object is not encoded in a particular frame of reference, but instead involves neurons computing basis functions of sensory inputs. In this type of representation, a nonlinear sensorimotor transformation of an object is represented in a population of units having the response properties of neurons that are observed in the parietal cortex. A simulated lesion in a basis–function representation was found to replicate three of the most important aspects of hemineglect: (i) the model behaved like parietal patients in line–cancellation and line–bisection experiments; (ii) the deficit affected multiple frames of reference; and (iii) the deficit could be object–centred. These results support the basis–function hypothesis for spatial representations and provide a testable computational theory of hemineglect at the level of single cells.

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Neural Representation of Space Using Sinusoidal Arrays

Neural Computation ◽

10.1162/neco.1993.5.6.869 ◽

1993 ◽

Vol 5 (6) ◽

pp. 869-884 ◽

Cited By ~ 40

Author(s):

David S. Touretzky ◽

A. David Redish ◽

Hank S. Wan

Keyword(s):

Computer Simulations ◽

Parietal Cortex ◽

Spatial Information ◽

Sine Wave ◽

Spiking Neurons ◽

Neural Representation ◽

Temporal Dimension ◽

Response Properties ◽

Representation Of Space

O'Keefe (1991) has proposed that spatial information in rats might be represented as phasors: phase and amplitude of a sine wave encoding angle and distance to a landmark. We describe computer simulations showing that operations on phasors can be efficiently realized by arrays of spiking neurons that recode the temporal dimension of the sine wave spatially. Some cells in motor and parietal cortex exhibit response properties compatible with this proposal.

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The Development of an Effective Bacterial Single-Cell Lysis Method Suitable for Whole Genome Amplification in Microfluidic Platforms

Micromachines ◽

10.3390/mi9080367 ◽

2018 ◽

Vol 9 (8) ◽

pp. 367 ◽

Cited By ~ 6

Author(s):

Yuguang Liu ◽

Dirk Schulze-Makuch ◽

Jean-Pierre de Vera ◽

Charles Cockell ◽

Thomas Leya ◽

...

Keyword(s):

Single Cell ◽

Single Cells ◽

Bacterial Species ◽

Cell Manipulation ◽

Microfluidic Platforms ◽

Gram Positive ◽

Gram Negative ◽

Genome Amplification ◽

Single Cell Sequencing ◽

Wide Range

Single-cell sequencing is a powerful technology that provides the capability of analyzing a single cell within a population. This technology is mostly coupled with microfluidic systems for controlled cell manipulation and precise fluid handling to shed light on the genomes of a wide range of cells. So far, single-cell sequencing has been focused mostly on human cells due to the ease of lysing the cells for genome amplification. The major challenges that bacterial species pose to genome amplification from single cells include the rigid bacterial cell walls and the need for an effective lysis protocol compatible with microfluidic platforms. In this work, we present a lysis protocol that can be used to extract genomic DNA from both gram-positive and gram-negative species without interfering with the amplification chemistry. Corynebacterium glutamicum was chosen as a typical gram-positive model and Nostoc sp. as a gram-negative model due to major challenges reported in previous studies. Our protocol is based on thermal and chemical lysis. We consider 80% of single-cell replicates that lead to >5 ng DNA after amplification as successful attempts. The protocol was directly applied to Gloeocapsa sp. and the single cells of the eukaryotic Sphaerocystis sp. and achieved a 100% success rate.

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"Creep currents" in single frog atrial cells may be generated by electrogenic Na/Ca exchange.

The Journal of General Physiology ◽

10.1085/jgp.87.6.857 ◽

1986 ◽

Vol 87 (6) ◽

pp. 857-884 ◽

Cited By ~ 49

Author(s):

J R Hume ◽

A Uehara

Keyword(s):

Voltage Clamp ◽

Time Course ◽

Single Cells ◽

Mechanical Activity ◽

Common Mechanism ◽

Mechanical Relaxation ◽

Equilibrium Conditions ◽

Atrial Cells ◽

Current Voltage ◽

Wide Range

The objective of these experiments was to test the hypothesis that the "creep currents" induced by Na loading of single frog atrial cells (Hume, J. R., and A. Uehara. 1986. Journal of General Physiology. 87:833) may be generated by an electrogenic Na/Ca exchanger. Creep currents induced by Na loading were examined over a wide range of membrane potentials. During depolarizing voltage-clamp pulses, outward creep currents were observed, followed by inward creep currents upon the return to the holding potential. During hyperpolarizing voltage-clamp pulses, creep currents of the opposite polarity were observed: inward creep currents were observed during the pulses, followed by outward creep currents upon the return to the holding potential. The current-voltage relations for inward and outward creep currents in response to depolarizing or hyperpolarizing voltage displacements away from the holding potential all intersect the voltage axis at a common potential, which indicates that inward and outward creep currents may have a common reversal potential under equilibrium conditions and may therefore be generated by a common mechanism. Measurements of inward creep currents confirm that voltage displacements away from the holding potential rapidly alter equilibrium conditions. Current-voltage relationships of inward creep currents after depolarizing voltage-clamp pulses are extremely labile and depend critically upon the amplitude and duration of outward creep currents elicited during preceding voltage-clamp pulses. An optical monitor of mechanical activity in single cells revealed (a) a similar voltage dependence for the outward creep currents induced by Na loading and tonic contraction, and (b) a close correlation between the time course of the decay of the inward creep current and the time course of mechanical relaxation. A mathematical model of electrogenic Na/Ca exchange (Mullins, L.J. 1979. Federation Proceedings. 35:2583; Noble, D. 1986. Cardiac Muscle. 171-200) can adequately account for many of the properties of creep currents. It is concluded that creep currents in single frog atrial cells may be attributed to the operation of an electrogenic Na/Ca exchange mechanism.

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A Methodology for Assessing Fuel Cell Performance Under a Wide Range of Operational Conditions: Results for Single Cells

Journal of Fuel Cell Science and Technology ◽

10.1115/1.2194558 ◽

2006 ◽

Vol 3 (3) ◽

pp. 226-233 ◽

Cited By ~ 1

Author(s):

Andrea Baratella ◽

Roberto Bove ◽

Piero Lunghi

Keyword(s):

Fuel Cells ◽

Fuel Cell ◽

Single Cells ◽

Cell Performance ◽

Effective Parameters ◽

Test Procedures ◽

Operational Conditions ◽

Fuel Cell Performance ◽

Wide Range ◽

The University

Testing the performance of fuel cells is an important key for verifying technology improvements and for demonstrating their potential. However, due to the novelty of this technology, there is not a standardized procedure for testing fuel cell performance. In order to fully investigate fuel cell performance, the behavior must be known under a wide range of operational conditions. Furthermore, in order to compare results coming from different test teams, a set of procedures and parameters to evaluate single cell performance should be defined. The research group of the Fuel Cell Laboratory of the University of Perugia is conducting performance tests on single cells, focusing on defining test procedures to find effective parameters to be used to compare tests performed by different teams. This work demonstrates how the testing parameters developed by the team allow one to perform advanced control on test procedures, to understand test results, and to compare them with tests carried out under different operational conditions. The entire analysis is easily conducted by using a single parameter variation hyperspace approach. The experimental results obtained on single fuel cells are reported.

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Space, Time, and Objects

10.1093/oxfordhb/9780195304787.003.0013 ◽

2009 ◽

Author(s):

Rick Grush

Keyword(s):

Nervous System ◽

Information Processing ◽

Basis Function ◽

Spatial Representation ◽

Space Time ◽

Function Model ◽

Temporal Representation ◽

Spatiotemporal Trajectories ◽

Processing Framework

This article outlines a unified information processing framework whose goal is to explain how the nervous system represents space, time, and objects. It explains the concept of the emulation theory of representation and describes an extension of the emulation framework for temporal representation. It discusses Alexandre Pouget's basis function model of spatial representation and describes how to combine the basis function model of spatial representation with the trajectory emulation model of temporal representation to yield an information processing framework that genuinely represents behavioral spatiotemporal trajectories of behavioral objects.

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Discriminative Learning and the Lexicon: NDL and LDL

10.1093/acrefore/9780199384655.013.375 ◽

2021 ◽

Author(s):

Yu-Ying Chuang ◽

R. Harald Baayen

Keyword(s):

Lexical Processing ◽

Morphological Processing ◽

Discriminative Learning ◽

Computational Algorithms ◽

Association Strength ◽

Computational Theory ◽

Wide Range ◽

Multivariate Multiple Regression ◽

Lexical Learning ◽

Set Up

Naive discriminative learning (NDL) and linear discriminative learning (LDL) are simple computational algorithms for lexical learning and lexical processing. Both NDL and LDL assume that learning is discriminative, driven by prediction error, and that it is this error that calibrates the association strength between input and output representations. Both words’ forms and their meanings are represented by numeric vectors, and mappings between forms and meanings are set up. For comprehension, form vectors predict meaning vectors. For production, meaning vectors map onto form vectors. These mappings can be learned incrementally, approximating how children learn the words of their language. Alternatively, optimal mappings representing the end state of learning can be estimated. The NDL and LDL algorithms are incorporated in a computational theory of the mental lexicon, the ‘discriminative lexicon’. The model shows good performance both with respect to production and comprehension accuracy, and for predicting aspects of lexical processing, including morphological processing, across a wide range of experiments. Since, mathematically, NDL and LDL implement multivariate multiple regression, the ‘discriminative lexicon’ provides a cognitively motivated statistical modeling approach to lexical processing.

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Aspiration-assisted bioprinting for precise positioning of biologics

Science Advances ◽

10.1126/sciadv.aaw5111 ◽

2020 ◽

Vol 6 (10) ◽

pp. eaaw5111 ◽

Cited By ~ 19

Author(s):

Bugra Ayan ◽

Dong Nyoung Heo ◽

Zhifeng Zhang ◽

Madhuri Dey ◽

Adomas Povilianskas ◽

...

Keyword(s):

Self Assembly ◽

Physical Mechanism ◽

Single Cells ◽

Three Dimensional ◽

3D Bioprinting ◽

Precise Control ◽

3D Space ◽

Magnitude Range ◽

Wide Range ◽

Order Of Magnitude

Three-dimensional (3D) bioprinting is an appealing approach for building tissues; however, bioprinting of mini-tissue blocks (i.e., spheroids) with precise control on their positioning in 3D space has been a major obstacle. Here, we unveil “aspiration-assisted bioprinting (AAB),” which enables picking and bioprinting biologics in 3D through harnessing the power of aspiration forces, and when coupled with microvalve bioprinting, it facilitated different biofabrication schemes including scaffold-based or scaffold-free bioprinting at an unprecedented placement precision, ~11% with respect to the spheroid size. We studied the underlying physical mechanism of AAB to understand interactions between aspirated viscoelastic spheroids and physical governing forces during aspiration and bioprinting. We bioprinted a wide range of biologics with dimensions in an order-of-magnitude range including tissue spheroids (80 to 600 μm), tissue strands (~800 μm), or single cells (electrocytes, ~400 μm), and as applications, we illustrated the patterning of angiogenic sprouting spheroids and self-assembly of osteogenic spheroids.

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Construction of 3D Cellular Composites with Stem Cells Derived from Adipose Tissue and Endothelial Cells by Use of Optical Tweezers in a Natural Polymer Solution

Materials ◽

10.3390/ma12111759 ◽

2019 ◽

Vol 12 (11) ◽

pp. 1759 ◽

Cited By ~ 1

Author(s):

Takehiro Yamazaki ◽

Toshifumi Kishimoto ◽

Paweł Leszczyński ◽

Koichiro Sadakane ◽

Takahiro Kenmotsu ◽

...

Keyword(s):

Stem Cells ◽

Endothelial Cells ◽

Adipose Tissue ◽

Optical Tweezers ◽

Single Cells ◽

Three Dimensional ◽

Cell Types ◽

Cellular Interactions ◽

Research Fields ◽

Wide Range

To better understand the regulation and function of cellular interactions, three-dimensional (3D) assemblies of single cells and subsequent functional analysis are gaining popularity in many research fields. While we have developed strategies to build stable cellular structures using optical tweezers in a minimally invasive state, methods for manipulating a wide range of cell types have yet to be established. To mimic organ-like structures, the construction of 3D cellular assemblies with variety of cell types is essential. Our recent studies have shown that the presence of nonspecific soluble polymers in aqueous solution is the key to creating stable 3D cellular assemblies efficiently. The present study further expands on the construction of 3D single cell assemblies using two different cell types. We have successfully generated 3D cellular assemblies, using GFP-labeled adipose tissue-derived stem cells and endothelial cells by using optical tweezers. Our findings will support the development of future applications to further characterize cellular interactions in tissue regeneration.

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What Neuroscientific Studies Tell Us about Inhibition of Return

Vision ◽

10.3390/vision3040058 ◽

2019 ◽

Vol 3 (4) ◽

pp. 58 ◽

Cited By ~ 2

Author(s):

Jason Satel ◽

Nicholas R. Wilson ◽

Raymond M. Klein

Keyword(s):

Inhibition Of Return ◽

Brain Activity ◽

Critical Role ◽

Direct Methods ◽

Brain Structures ◽

Developmental Studies ◽

Unit Recording ◽

Wide Range ◽

Lesion Studies

An inhibitory aftermath of orienting, inhibition of return (IOR), has intrigued scholars since its discovery about 40 years ago. Since then, the phenomenon has been subjected to a wide range of neuroscientific methods and the results of these are reviewed in this paper. These include direct manipulations of brain structures (which occur naturally in brain damage and disease or experimentally as in TMS and lesion studies) and measurements of brain activity (in humans using EEG and fMRI and in animals using single unit recording). A variety of less direct methods (e.g., computational modeling, developmental studies, etc.) have also been used. The findings from this wide range of methods support the critical role of subcortical and cortical oculomotor pathways in the generation and nature of IOR.

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Chaotic Balanced State in a Model of Cortical Circuits

Neural Computation ◽

10.1162/089976698300017214 ◽

1998 ◽

Vol 10 (6) ◽

pp. 1321-1371 ◽

Cited By ~ 448

Author(s):

C. van Vreeswijk ◽

H. Sompolinsky

Keyword(s):

Cortical Neurons ◽

Initial Conditions ◽

Single Cells ◽

Network Size ◽

Short Time Scale ◽

Strong Nonlinearity ◽

Large Network ◽

Wide Range ◽

The Mean

The nature and origin of the temporal irregularity in the electrical activity of cortical neurons in vivo are not well understood. We consider the hypothesis that this irregularity is due to a balance of excitatory and inhibitory currents into the cortical cells. We study a network model with excitatory and inhibitory populations of simple binary units. The internal feedback is mediated by relatively large synaptic strengths, so that the magnitude of the total excitatory and inhibitory feedback is much larger than the neuronal threshold. The connectivity is random and sparse. The mean number of connections per unit is large, though small compared to the total number of cells in the network. The network also receives a large, temporally regular input from external sources. We present an analytical solution of the mean-field theory of this model, which is exact in the limit of large network size. This theory reveals a new cooperative stationary state of large networks, which we term a balanced state. In this state, a balance between the excitatory and inhibitory inputs emerges dynamically for a wide range of parameters, resulting in a net input whose temporal fluctuations are of the same order as its mean. The internal synaptic inputs act as a strong negative feedback, which linearizes the population responses to the external drive despite the strong nonlinearity of the individual cells. This feedback also greatly stabilizes the system's state and enables it to track a time-dependent input on time scales much shorter than the time constant of a single cell. The spatiotemporal statistics of the balanced state are calculated. It is shown that the autocorrelations decay on a short time scale, yielding an approximate Poissonian temporal statistics. The activity levels of single cells are broadly distributed, and their distribution exhibits a skewed shape with a long power-law tail. The chaotic nature of the balanced state is revealed by showing that the evolution of the microscopic state of the network is extremely sensitive to small deviations in its initial conditions. The balanced state generated by the sparse, strong connections is an asynchronous chaotic state. It is accompanied by weak spatial cross-correlations, the strength of which vanishes in the limit of large network size. This is in contrast to the synchronized chaotic states exhibited by more conventional network models with high connectivity of weak synapses.

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