Analysis of multichannel intermuscular coupling characteristics during rehabilitation after stroke / 生物医学工程学杂志

To better analyze the problem of abnormal neuromuscular coupling related to motor dysfunction for stroke patients, the functional coupling of the multichannel electromyography (EMG) were studied and the difference between stroke patients and healthy subjects were further analyzed to explore the pathological mechanism of motor dysfunction after stroke. Firstly, the cross-frequency coherence (CFC) analysis and non-negative matrix factorization (NMF) were combined to construct a CFC-NMF model to study the linear coupling relationship in bands and the nonlinear coupling characteristics in different frequency ratios during elbow flexion and extension movement. Furthermore, the significant coherent area and sum of cross-frequency coherence were respectively calculated to quantitatively describe the intermuscular linear and nonlinear coupling characteristics. The results showed that the linear coupling relationship between multichannel muscles was different in frequency bands and the overall coupling was stronger in low frequency band. The linear coupling strength of the stroke patients was lower than that of the healthy subjects in different frequency bands especially in beta and gamma bands. For the nonlinear coupling, the intermuscular coupling strength of stroke patients in different frequency ratios was significantly lower than that of the healthy subjects, and the coupling strength in the frequency ratio 1∶2 was higher than that in the frequency ratio 1∶3. This method can provide a theoretical basis for exploring the intermuscular coupling mechanism of patients with motor dysfunction.

Analysis of negative and non-negative uses of nā, particle of negation in Bengali.

The present paper consists of a linguistic analysis of different uses of the particle nā in Bengali. For any native speaker of the language, it is the particle of negation denoting absence or non-existence. Equivalent of no and not in English, nā however has a much wider use. We find many instances where nā, unlike its counterparts in English fulfils, at least apparently no negative function. Nā in such cases is redundant ; its omission does not render the sentence incorrect at the syntactic level , nor does it lead to any change in the semantic content of the proposition.This nā is termed in traditional Bengali grammar as bakyalankarbachak abyay i.e. expletive indeclinable. The aim of this article is to demonstrate that the apparently non-negative nā performs actually a negative role, though in a different sense. The secondary non-negative uses of nā are in absolute conformity with the fundamental characteristic of nā, the particle of negation. Through an in depth study of examples of negative and non-negative uses of nā we have attempted to bring out the unifying factor.

Non-negative matrix factorization with sparseness constraints for neural activity in rat prefrontal cortex during working memory task / 国际生物医学工程杂志

Objective To analyze neural activity of in rat prefrontal cortex with the use of nonnegative matrix factorization with sparseness constrains (NMFs) as a methodology and to study how to express neural ensemble with higher precision during working memory task.Methods Experiment data were obtained from neural population activity in the period 5 s before and after the working memory event.From the zero point,the neuronal firing times were binned in windows of 200 ms with 50 ms overlapping.The normalized neuronal bin-count matrix is decomposed by NMFs into mixing matrix and source component matrix with sparseness constraints.Meaningful components were extracted to reconstruct the input by an inverse of NMFs transform.Results By analyzing the ten groups of data from 2 rats,with the numbers of the sparse sources of 10 and 15 respectively,explicit neural ensembles with the feature components were obtained in the sparse reconstructed activity.Comparing to rate coding,the spatiotemporal location of neural ensemble was more precisely detected.Conclusion The working memory information is encoded with neural ensemble activity.NMFs could find the sparse firing pattern robustly in neuron population activity.NMFs removes much redundancy and demonstrate the possibility to express neural ensemble with higher precision compared with rate coding,which would be helpful to infer correlations between cortical firing pattern and working memory event.

Deducing Isoform Abundance from Exon Junction Microarray

Alternative splicing (AS) is an important mechanism of producing transcriptome diversity and microarray techniques are being used increasingly to monitor the splice variants. There exist three types of microarrays interrogating AS events-junction, exon, and tiling arrays. Junction probes have the advantage of monitoring the splice site directly. Johnson et al., performed a genome-wide survey of human alternative pre-mRNA splicing with exon junction microarrays (Science 302:2141-2144, 2003), which monitored splicing at every known exon-exon junctions for more than 10,000 multi-exon human genes in 52 tissues and cell lines. Here, we describe an algorithm to deduce the relative concentration of isoforms from the junction array data. Non-negative Matrix Factorization (NMF) is applied to obtain the transcript structure inferred from the expression data. Then we choose the transcript models consistent with the ECgene model of alternative splicing which is based on mRNA and EST alignment. The probe-transcript matrix is constructed using the NMF-consistent ECgene transcripts, and the isoform abundance is deduced from the non-negative least squares (NNLS) fitting of experimental data. Our method can be easily extended to other types of microarrays with exon or junction probes.