Search PubMed⌕ Search

Biomedical subjects

Zhisong Wang

Publications and source records attributed to Zhisong Wang.

5 recordsLinked to original sources
PubMed2006

Single-trial evoked potential estimation using wavelets.

In this paper we present conventional and translation-invariant (TI) wavelet-based approaches for single-trial evoked potential estimation based on intracortical recordings. We demonstrate that the wavelet-based approaches outperform several existing methods including the Wiener filter, least mean square (LMS), and recursive least squares (RLS), and that the TI wavelet-based estimates have higher SNR and lower RMSE than the conventional wavelet-based estimates. We also show that multichannel averaging significantly improves the evoked potential estimation, especially for the wavelet-based approaches. The excellent performances of the wavelet-based approaches for extracting evoked potentials are demonstrated via examples using simulated and experimental data.

Algorithms↗
PubMed2006

Relaxation-based multichannel signal combination (RELAX-MUSIC) for ROC analysis of percept-related neuronal activity.

In this letter, we consider how to combine neuronal signals from multiple electrodes to optimally predict behavioral choices from observed neural activity. The predictability is often quantified by the area under the receiver operating characteristic (ROC) curve, also called choice probability (CP) in neurophysiology. We exploit a distribution-free relaxation based multichannel signal combination (RELAX-MUSIC) approach that requires only simple pairwise combination and recursive implementation for optimizing the area under the ROC curve. A permutation test is employed to assess the statistical significance of the derived CP. We demonstrate that the RELAX-MUSIC approach outperforms the commonly used response pooling and Fisher linear discriminant (FLD) methods. The excellent performances of the RELAX-MUSIC approach for predicting perceptual decisions from neural activity are demonstrated via examples using simulated and experimental data.

Action Potentials↗
PubMed2005

Time-delay- and time-reversal-based robust Capon beamformers for ultrasound imaging.

Currently, the nonadaptive delay-and-sum (DAS) beamformer is extensively used for ultrasound imaging, despite the fact that it has lower resolution and worse interference suppression capability than the adaptive standard Capon beamformer (SCB) if the steering vector corresponding to the signal of interest (SOI) is accurately known. The main problem which restricts the use of SCB, however, is that SCB lacks robustness against steering vector errors that are inevitable in practice. Whenever this happens, the performance of SCB may hecome worse than that of DAS. Therefore, a robust adaptive beamformer is desirable to maintain the robustness of DAS and adaptivity of SCB. In this paper we consider a recent promising robust Capon beamformer (RCB) for ultrasound imaging. We propose two ways of implementing RCB, one based on time delay and the other based on time reversal. RCB extends SCB by allowing the array steering vector to be within an uncertainty set. Hence, it restores the appeal of SCB including its high resolution and superb interference suppression capabilities, and also retains the attractiveness of DAS including its robustness against steering vector errors. The time-delay-based RCB can tolerate the misalignment of data samples and the time-reversal-based RCB can withstand the uncertainty of the Green's function. Both time-delay-based RCB and time-reversal-based RCB can be efficiently computed at a comparable cost to SCB. The excellent performances of the proposed robust adaptive beamforming approaches are demonstrated via a number of simulated and experimental examples.

Algorithms↗
PubMed2004

Bioinspired laser-operated molecular locomotive.

Biomotors kinesin and dynein show us that robust track-walking is possible down to molecular scale. Here I design a laser-powered molecular locomotive that is able to do that on an easily constructed track. The core of the machine is its work cycle that periodically converts optical energy into mechanical work, which is further rectified into processive, directional motion. Thus the molecular locomotive is essentially beyond the famous design of molecular shuttles. Under automated laser operation, the locomotive can move a few mum per second comparable to its biological counterparts. However, this artificial motor is capable of conveniently switchable, dual directional motion in contrast to common unidirectionality of biomotors. The locomotive is also different from the big category of Brownian motors in the sense that move of the locomotive is not a result of biasing pre-existing fluctuations, rather it is directly and decisively driven by optomechanical strokes of the work cycle, generating a pulling force ten times greater than those of biomotors. Being a novel type of molecular motor as well as a powerful molecular engine, this machine will potentially enable automatic, forceful delivery of molecular building blocks with nanometer accuracy. Well within reach of established techniques, its implementation will be a significant advance in nanoscience and nanotechnology.

Biomimetic Materials↗