# Entropy and Statistical Complexity in Bioelectrical Signals: A Literature Review
## 4 Discussion
### Application of Entropies in the Analysis of Biomedical Signals
\begin{table}
\begin{tabular}{c c c} \hline
**Category** & **Application/Paper** & **Details** \\ \hline Electroencephalogram EEG & Permutation entropy & [28; 50; 52] \\ \hline Sample entropy & [29; 36; 52] \\ \hline Multiscale entropy (MSE) & [36; 50; 52] \\ \hline Approximate entropy & [36; 52] \\ \hline Tsallis entropy & [36] \\ \hline Medical EEG perspective & Monitoring brain activity & [28; 29; 36] \\ \hline Complexity and uncertainty in biomedical datasets & [36] \\ \hline Complexity across different time periods & [50] \\ \hline Signal inconsistency & [28; 36] \\ \hline Parkinson’s disease (PD) & [36] \\ \hline Alzheimer’s disease (AD) & [29; 50] \\ \hline Electrogastrography EGG & Digestive disorders using Tsallis and Renyi entropy & [72] \\ \hline Electrode size in EGG measurements using Renyi entropy & [73] \\ \hline \end{tabular} Source: Own design.  
\end{table} 
Table 2: Applications of entropy methods in EEG and EGG analysis for biomedical research. information contained in EGG signals, the study concludes that a broader informational spectrum can be captured with electrodes of greater surface area [73]. Additionally, among the most commonly used entropy measures in the medical field, there are as follows (see Table 3): first, Permutation Entropy currently applied in disciplines such as biology [49] to study, for instance, dynamic variations induced by musical stimuli in subjects with Alzheimer's disease (AD) at different stages [46]. Second, Fuzzy Entropy is used to identify Alzheimer's disease (AD) [29], as well as to detect epileptic seizures and investigate the dynamics of lung cancer through imaging techniques [35], among other applications. Third, Approximate Entropy (ApEn) has been extensively employed in the analysis of time series of physiological variables to evaluate their degree of randomness [9] and to assess irregularities in signals generated by disordered biological systems [22]. Among other applications, it has been used to identify Alzheimer's disease (AD) [29] and to detect changes in heart rate. Fourth, Sample Entropy (SampEn) is used, among other applications, to identify Alzheimer's disease (AD) [29]; to study heart rate and conduct cardiovascular clinical studies [10; 35]; as a promising biomarker for Parkinson's disease (PD), including its progression [19]; to analyze complexity in voice disorders [22]; and extensively in various practical applications, including emotion assessment and evaluating signals from magnetic resonance imaging (MRI) [35]. Fifth, Multiscale Entropy (MSE) has been used, among other applications, in the analysis of sleep in patients with and without apnea, as well as for analyzing physiological signals obtained from electrocardiography (ECG) [40]. The findings of this research highlight the use of EEG signals for the detection of neurodegenerative diseases such as Alzheimer's disease (AD) and Parkinson's disease (PD) through the application of entropic quantifiers, including PermEn, FuzzyEn, ApEn, SampEn, and MSE. These advancements underscore the potential of ITQs in the analysis of \begin{table}
\begin{tabular}{c c c} \hline \hline
**Category** & **Application/Paper** & **Details** \\ \hline Permutation entropy & Biology & [49] \\ \hline  & Alzheimer & [46] \\ \hline Fuzzy entropy & Alzheimer & [29] \\ \hline  & Lung cancer & [35] \\ \hline Approximate entropy, ApEn & Time series with physiological variables & [9] \\ \hline  & Unordered biological systems & [22] \\ \hline  & Alzheimer & [29] \\ \hline  & Changes in heart rate & [18] \\ \hline Sample entropy, SampEn & Alzheimer & [29] \\ \hline  & Heart rate & [10; 35] \\ \hline  & Parkinson & [19] \\ \hline  & Voice disorders & [22] \\ \hline  & Magnetic resonance & [35] \\ \hline Multiscale entropy, MSE & Sleep analysis with physiological signals & [40] \\ \hline Multiscale increment entropy, MIE & Physiological complexity in temporal scales & [53] \\ \hline \hline \end{tabular} Source: Own design.  
\end{table} 
Table 3: Applications of entropy metrics in biomedical and physiological studies.