Wavelet Coherence and Its Application in Analyzing Auditory and Motor Task Event-Related Potentials

WU Jie，ZHANG Ning，YANG Zhuo，ZHANG Tao, Wavelet coherence and its application in analyzing auditory and motor task event-related potentials.

This paper has been accepted by ACTA BIOPYSICA SINICA，here is its abstract.

Related links:Tips about Wavelet , Wavelet Coherence Method,A Vivid Example to Show How Wavelet Coherence Works, Some Concepts about ERP signals ,Wavelet and EEG Signals. These links can help to gain further information about this paper.

Abstract:
Wavelet coherence method is applied in analyzing single trial of ERP (event-related potential). There are three groups of experiments: auditory single task, motor single task 1 and motor single task 2. Data from 12 participants is analyzed around 40 Hz by wavelet coherence method and the coherence values between prefrontal area and other areas in the brain are calculated. It is found that the coherence values in motor tasks are larger than those in auditory task and there are significantly differences. Furthermore, in different tasks, the distributions of the coherence values are obviously different, and the values are changing in particularly ways according the varying of the time. This analysis indicates that wavelet coherence method has its advantages in investigating short time EEG signals.

Brief descriptions:


The coherence values, around 40Hz between prefrontal area and other areas in the cerebral cortex, were measured. It was found that the coherence values in the MST (Motor Single Task) are larger than that in the AST (Auditory Single Task) with significant differences.Brain dealing with complicated tasks can have more information to process, and there should be more information communication between different areas of the brain. This can be denoted by coherence values.


Wavelet Coherence Values along the time axis. The colors in the images indicate the coherence values between prefrontal area and other areas in the cerebral cortex around 40Hz(the relationship between the color and the value is shown in the color-bar).large coherence values exactly locate in Auditory Cortex at temporal lobe in AST conditions, whilst in MST conditions, the big values are in motor cortex which is in parietal area.

The data show that the wavelet methods calculations of non-stationary signals, compared to the Fourier methods, can characterize the time-frequency features of neural mechanisms underlying cognitive control. Furthermore, wavelet approach can provide higher resolution in both temporal and spatial scales and can be applied in analyzing other physiological signals.

Main reference:
Lachaux, J.-P., et al., Estimating the time-course of coherence between single-trial brain signals: an introduction to wavelet coherence. Neurophysiol Clin., 2002. 32: p. 157-174.

Wavelet Analysis of ERP Recordings for Dual Tasks in Man

WU J, YANG Z, ZHANG T, Wavelet analysis of ERP recordings for dual tasks in man.

This paper has been accepted by ICCN'07 & SICPB'07 which will be held in Shanghai, China during November 17-21, 2007. The abstract is shown as below.

Click Wavelet Packet Transform, Relative Wavelet Energy, ERP for more relevant information.

Abstract:
The study was to examine the application of wavelet packet method to electrophysiological responses recorded during single and dual task performance. Relative energies of both EEG alpha and beta frequency bands were significantly higher in the single task conditions compared with that of the dual task condition (P is less than 0.05). The data demonstrated that relative energy measurements based on wavelet transform could be a useful alternative approach to analyzing short duration EEG signals on a time scale of seconds.

It is impossible and unnecessary to show the details of this paper in a single short article, so only the abstract is shown here.

The most important point is that, compared to the Fourier methods, wavelet method can be an alternative and much better method to deal with short time EEG signals. Accordingly, wavelet method can be used in analyzing other data in our lab, those data include EEG, ERP and RSNA signals. They are all complicated signals and represent nonlinear dynamic systems with high dimensionality.

There will be other artcles in this blog to illustrate the advantages of Wavelet method compared to regular frequency analysis methods.

ERPDB: a Database of ERP Data for Neuroinformatics Research

Event-related potential (ERP) is the measurement of the brain's electrical activity in response to different types of events. These signals are useful for learning how information is processed in the human brain. Being a neuroinformatics laboratory, we deal with lots of ERP signals, which come from various research programs. Different programs have different experiment designs, different parameters settings, and different data formats. These could be big problems for our study. For this reason, arranging the data and constructing a database to store them is quite necessary.

ERPDB contains the information of the participants and the rearranged signals.The data have been transformed into more organized data, which are more convenient for further computation and analysis. Also, new data can be easily added into the database according to our standard. This database is available on the web.



Publications:
Qinghong Yan, Ning Zhang, Jie Wu. The Constitution of ERP Database Based on SQL Server2000. The 20th International CODATA Conference (CODATA2006 ABSTRACT，China，Beijing):2006, 308
QingHong Yan, Ning Zhang, Jie Wu, Tao Zhang. ERPDB: an integrated database of ERP datafor neuroinformatics research, Data science journal, 2007

SheetsPair: a Database of Amino Acids Pairs in Protein Sheet Structures

Sheet is a basic secondary structural element of proteins. To provide a data resource for further analysis on "Sheet", a database which contains a large number of sheet structures was constructed.


The protein dataset utilized to populate the database was obtained from PDB, excluding those that have no sheet structure and those with modified residues, that is, the database is rigorous, precise and faithworthy, with no uncertain residues or modified residues or uncertain structures. The database now contains a total of 756,897 amino acids pairs in sheet structures of 10,704 proteins. There are more details in the publications.

The website interface is shown below:

Publication:

Ning Zhang, Jie Wu, Tao Zhang. SheetsPair: a database of amino acids pairs in protein sheetstructures. The 20th International CODATA Conference (CODATA2006 ABSTRACT，China，Beijing): 295

Ning Zhang, Jishou Ruan, Jie Wu, Tao Zhang. SheetsPair: a database of amino acids pairs inprotein sheet structures, Data science journal, 2007

An Epilepsy EEG Database

Research on Epilepsy EEG is a big part in our lab-- Biocomputation and Neuroinformatics Laboratory. By analyzing the EEG signals in rat models, we aim to find some way to predict seizures before they begin, which could be helpful for treatment of epilepsy. Some samples of human epilepsy EEG were also collected from hospitals and research centers. For the data formats are distinctive, there was some problems to analyze them together.

Being a preparation for a further investigation, an EEG database was constituted. EEG signals from healthy and epilepsy humans together with the annotations were collected and standardized in this database.

The website of this database is shown as below.



Publication: Zhang Ning,Wu Jie,Yang Zhuo,et al,Constitution of an EEG database based on SQL server. Chinese Chinese High Technology Letters,2006,16(12): 48-52.