# Selection of Mother Wavelet Functions for Multi-Channel EEG Signal Analysis during a Working Memory Task

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## Abstract

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## 1. Introduction

## 2. Methods

#### 2.1. Subjects and EEG Recording Procedure

**Table 1.**Sociodemographic data of the control subjects. Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA) scores are also shown, (Age in years, MMSE and MoCA, mean ± standard deviation SD).

Demographic and Clinical Features | Control |
---|---|

Number | 10 |

Age | 47.9 ± 6.5 |

MMSE | 29.7 ± 0.67 |

MoCA | 28.9 ± 0.87 |

Female/Male | 4F/6M |

**Figure 3.**The EEG activities for a healthy subject during a working memory task using the NicoletOne systems (V32).

#### 2.2. Wavelet Analysis

#### 2.2.1. Mother Wavelet Optimal Selection

**Figure 4.**The block diagram of the correlation between the noisy EEG signals and denoised EEG signals using mother wavelet families.

**Figure 5.**Noisy EEG epochs and mother wavelet of Daubechies (db order from 2 to 5), Coiflets (coif order from 2 to 5) and symlet (sym order from 1 to 9) representation.

#### 2.2.2. Level of Decomposition and Threshold Selection

Decomposition Levels | Frequency Bands (Hz) | Decomposed Signals | EEG Bands |
---|---|---|---|

1 | 64–128 | D1 | Higher gamma and noise |

2 | 32–64 | D2 | Lower gamma (γ) |

3 | 16–32 | D3 | Beta (β) |

4 | 8–16 | D4 | Alpha (α) |

5 | 4–8 | D5 | Theta (θ) |

5 | 0–4 | A5 | Delta (δ) |

#### 2.3. Statistical Analysis

## 3. Results and Discussion

**Figure 7.**Comparative plot of correlation coefficients with 45 mother wavelet filter for the frontal region of the brain for 10 control subjects.

**Figure 8.**Comparative plot of correlation coefficients with 45 mother wavelet filter for the temporal region of the brain for 10 control subjects.

**Figure 9.**Comparative plot of correlation coefficients with 45 mother wavelet filter for the parietal region of the brain for 10 control subjects.

**Figure 10.**Comparative plot of correlation coefficients with 45 mother wavelet filter for the occipital region of the brain for 10 control subjects.

**Figure 11.**Comparative plot of correlation coefficients with 45 mother wavelet filter for the central region of the brain for 10 control subjects.

**Figure 12.**The removal results after the “sym9” MWT were applied on the EEG channels, the EEG signals before artifact removal (in red), the EEG signals after denoising (in blue).

**Figure 13.**Comparative plot of the relative powers after using “sym9” wavelet filter for the five scalp regions of the brain for 10 control subjects.

## 4. Conclusions

**Figure 14.**Comparative plot of the correlation coefficients with 45 mother wavelet filter for the 5 regions of the brain for 10 control subjects.

## Acknowledgments

## Author Contributions

## Conflicts of Interest

## References

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**MDPI and ACS Style**

Al-Qazzaz, N.K.; Hamid Bin Mohd Ali, S.; Ahmad, S.A.; Islam, M.S.; Escudero, J.
Selection of Mother Wavelet Functions for Multi-Channel EEG Signal Analysis during a Working Memory Task. *Sensors* **2015**, *15*, 29015-29035.
https://doi.org/10.3390/s151129015

**AMA Style**

Al-Qazzaz NK, Hamid Bin Mohd Ali S, Ahmad SA, Islam MS, Escudero J.
Selection of Mother Wavelet Functions for Multi-Channel EEG Signal Analysis during a Working Memory Task. *Sensors*. 2015; 15(11):29015-29035.
https://doi.org/10.3390/s151129015

**Chicago/Turabian Style**

Al-Qazzaz, Noor Kamal, Sawal Hamid Bin Mohd Ali, Siti Anom Ahmad, Mohd Shabiul Islam, and Javier Escudero.
2015. "Selection of Mother Wavelet Functions for Multi-Channel EEG Signal Analysis during a Working Memory Task" *Sensors* 15, no. 11: 29015-29035.
https://doi.org/10.3390/s151129015