Automatic neonatal sleep stage classification:A comparative study

Sleep is an essential feature of living beings. For neonates, it is vital for their mental and physical development. Sleep stage cycling is an important parameter to assess neonatal brain and physical development. Therefore, it is crucial to administer newborn's sleep in the neonatal intensive care unit (NICU). Currently, Polysomnography (PSG) is used as a gold standard method for classifying neonatal sleep patterns, but it is expensive and requires a lot of human involvement. Over the last two decades, multiple researchers are working on automatic sleep stage classification algorithms using electroencephalography (EEG), electrocardiography (ECG), and video. In this study, we present a comprehensive review of existing algorithms for neonatal sleep, their limitations and future recommendations. Additionally, a brief comparison of the extracted features, classification algorithms and evaluation parameters is reported in the proposed study

Automatic neonatal sleep stage classification: A comparative study

Sleep is an essential feature of living beings. For neonates, it is vital for their mental and physical development. Sleep stage cycling is an important parameter to assess neonatal brain and physical development. Therefore, it is crucial to administer newborn's sleep in the neonatal intensive care unit (NICU). Currently, Polysomnography (PSG) is used as a gold standard method for classifying neonatal sleep patterns, but it is expensive and requires a lot of human involvement. Over the last two decades, multiple researchers are working on automatic sleep stage classification algorithms using electroencephalography (EEG), electrocardiography (ECG), and video. In this study, we present a comprehensive review of existing algorithms for neonatal sleep, their limitations and future recommendations. Additionally, a brief comparison of the extracted features, classification algorithms and evaluation parameters is reported in the proposed study

L-Tetrolet Pattern-Based Sleep Stage Classification Model Using Balanced EEG Datasets

Background: Sleep stage classification is a crucial process for the diagnosis of sleep or sleep-related diseases. Currently, this process is based on manual electroencephalogram (EEG) analysis, which is resource-intensive and error-prone. Various machine learning models have been recommended to standardize and automate the analysis process to address these problems. Materials and methods: The well-known cyclic alternating pattern (CAP) sleep dataset is used to train and test an L-tetrolet pattern-based sleep stage classification model in this research. By using this dataset, the following three cases are created, and they are: Insomnia, Normal, and Fused cases. For each of these cases, the machine learning model is tasked with identifying six sleep stages. The model is structured in terms of feature generation, feature selection, and classification. Feature generation is established with a new L-tetrolet (Tetris letter) function and multiple pooling decomposition for level creation. We fuse ReliefF and iterative neighborhood component analysis (INCA) feature selection using a threshold value. The hybrid and iterative feature selectors are named threshold selection-based ReliefF and INCA (TSRFINCA). The selected features are classified using a cubic support vector machine. Results: The presented L-tetrolet pattern and TSRFINCA-based sleep stage classification model yield 95.43%, 91.05%, and 92.31% accuracies for Insomnia, Normal dataset, and Fused cases, respectively. Conclusion: The recommended L-tetrolet pattern and TSRFINCA-based model push the envelope of current knowledge engineering by accurately classifying sleep stages even in the presence of sleep disorders.</jats:p

Data Augmentation for Deep-Learning-Based Electroencephalography

Background: Data augmentation (DA) has recently been demonstrated to achieve considerable performance gains for deep learning (DL)—increased accuracy and stability and reduced overfitting. Some electroencephalography (EEG) tasks suffer from low samples-to-features ratio, severely reducing DL effectiveness. DA with DL thus holds transformative promise for EEG processing, possibly like DL revolutionized computer vision, etc. New method: We review trends and approaches to DA for DL in EEG to address: Which DA approaches exist and are common for which EEG tasks? What input features are used? And, what kind of accuracy gain can be expected? Results: DA for DL on EEG begun 5 years ago and is steadily used more. We grouped DA techniques (noise addition, generative adversarial networks, sliding windows, sampling, Fourier transform, recombination of segmentation, and others) and EEG tasks (into seizure detection, sleep stages, motor imagery, mental workload, emotion recognition, motor tasks, and visual tasks). DA efficacy across techniques varied considerably. Noise addition and sliding windows provided the highest accuracy boost; mental workload most benefitted from DA. Sliding window, noise addition, and sampling methods most common for seizure detection, mental workload, and sleep stages, respectively. Comparing with existing methods: Percent of decoding accuracy explained by DA beyond unaugmented accuracy varied between 8% for recombination of segmentation and 36% for noise addition and from 14% for motor imagery to 56% for mental workload—29% on average. Conclusions: DA increasingly used and considerably improved DL decoding accuracy on EEG. Additional publications—if adhering to our reporting guidelines—will facilitate more detailed analysis

Data Augmentation for Deep-Learning-Based Electroencephalography

Background: Data augmentation (DA) has recently been demonstrated to achieve considerable performance gains for deep learning (DL)—increased accuracy and stability and reduced overfitting. Some electroencephalography (EEG) tasks suffer from low samples-to-features ratio, severely reducing DL effectiveness. DA with DL thus holds transformative promise for EEG processing, possibly like DL revolutionized computer vision, etc. New method: We review trends and approaches to DA for DL in EEG to address: Which DA approaches exist and are common for which EEG tasks? What input features are used? And, what kind of accuracy gain can be expected? Results: DA for DL on EEG begun 5 years ago and is steadily used more. We grouped DA techniques (noise addition, generative adversarial networks, sliding windows, sampling, Fourier transform, recombination of segmentation, and others) and EEG tasks (into seizure detection, sleep stages, motor imagery, mental workload, emotion recognition, motor tasks, and visual tasks). DA efficacy across techniques varied considerably. Noise addition and sliding windows provided the highest accuracy boost; mental workload most benefitted from DA. Sliding window, noise addition, and sampling methods most common for seizure detection, mental workload, and sleep stages, respectively. Comparing with existing methods: Percent of decoding accuracy explained by DA beyond unaugmented accuracy varied between 8% for recombination of segmentation and 36% for noise addition and from 14% for motor imagery to 56% for mental workload—29% on average. Conclusions: DA increasingly used and considerably improved DL decoding accuracy on EEG. Additional publications—if adhering to our reporting guidelines—will facilitate more detailed analysis

Análisis de electroencefalogramas para la detección automática de las fases del sueño

Las enfermedades del sueño son cada vez más comunes debido al estresante estilo de vida de la sociedad actual. Un paso fundamental en su estudio y diagnóstico es detectar correctamente las diferentes fases del sueño. Avances en áreas como el Deep learning han permitido desarrollar métodos que automatizan esta detección, presentando una alternativa a la clasificación mediante inspección visual realizada hasta la fecha. En este trabajo se ha indagado en el uso de redes neuronales convolucionales (CNN) como clasificadores de fases del sueño, usando para ello la señal de electroencefalograma (EEG). El comportamiento de esta señal difiere entre niños y adultos. Sin embargo, los estudios publicados hasta ahora se han centrado únicamente en pacientes adultos, lo que provoca que los modelos de clasificación no sean fácilmente generalizables. Conseguir un método de clasificación basado en CNN que permita una detección precisa de las fases del sueño en niños, y comprobar si se puede entrenar un modelo que alcance resultados óptimos al evaluar sujetos de diferentes edades, son los objetivos principales de este trabajo. Para ello, se han usado dos amplias bases de datos públicas procedentes de los estudios Sleep Heart Health Study (SHHS) y Childhood Adenotonsillectomy Trial (CHAT), que contienen 5793 registros de adultos y 453 registros de niños, respectivamente. El proceso de entrenamiento y optimización de la red CNN se ha probado modificando el número de capas y su parámetro de regularización, este último buscando asegurar que no haya sobreentrenamiento. Tras conseguir un modelo con alto rendimiento al clasificar la población adulta, se ha evaluado dicho modelo en los registros pediátricos. El mismo procedimiento se ha realizado de manera inversa, probando en la población adulta un modelo entrenado únicamente con niños. Además, se ha obtenido un modelo conjunto usando registros de ambas bases de datos en los grupos de entrenamiento/validación/test. Para homogeneizar las señales de las dos bases, se ha implementado re-muestreo a la misma frecuencia, re-referenciado a la media de los canales utilizados en cada caso, y estandarización para igualar los límites de amplitud. Los resultados muestran que los modelos entrenados con registros de una única base de datos clasifican con alta precisión siempre que se apliquen sobre sujetos en los mismos rangos de edad, consiguiéndose una precisión del 0.815 y un kappa de Cohen de 0.738 en el caso de sujetos adultos y precisión de 0.84 y kappa de 0.77 en el caso de niños, lo que es coherente con estudios previos. No obstante, al clasificar un grupo de edad diferente, estos valores disminuyen. Sin embargo, el modelo entrenado con registros de diferentes edades sí que consigue detectar de manera precisa registros de ambas bases, llegando a una precisión de 0.81 y a un kappa de 0.75 al evaluarlo en un grupo de test conjunto. Estos resultados sugieren la necesidad de incluir sujetos de diferentes edades en el entrenamiento para conseguir modelos más generalizables.Sleep disorders are very common nowadays due to the stressful lifestyle of the current society. A fundamental step in the study and diagnosis of these disorders is to successfully detect the different sleep stages. Recent investigation in fields like Deep learning has led to the development of methods that automatize this detection, becoming an alternative to the visual classification mostly used up to the date. This project explores the application of convolutional neural networks (CNN) as methods for sleep staging classification, using the brain signal of the electroencephalogram (EEG). The behavior of this signal changes between children and adults. However, studies published up to the date mostly focus on grown up patients, issue that causes a poor generalization of the classification models when applied to other age ranges. Finding a classification method based on CNN that shows an accurate detection of children´s sleep stages, and training a model that reaches high performance when evaluated with subjects of different ages, are the two main goals of this work. In order to achieve these goals, two large public data bases have been used, coming from the Sleep Heart Health Study (SHHS) and the Childhood Adenotonsillectomy Trial (CHAT), and containing 5793 adults´ recordings and 453 children´s recordings, respectively. The process of training and optimizing the neural network has been conducted by varying the number of convolutional layers and the dropout percentage, the latter being used to minimize the risk of model overfitting. Once an effective model for the classification of adults´ recordings is found, it gets tested with the pediatric recordings. The same procedure is followed the other way around, testing with the recordings of adults a model trained only using kids´ signals. Furthermore, a mixed model is obtained by including subjects from both data bases in the training/validation/test groups. With the aim of homogenize the signals of the two data bases, three different actions have been taken: re-sampling the recordings to the same frequency, applying an average reference, and standardizing the signals to keep them with in the same amplitude limits. The results show that the models trained with just one of the data bases only classify accurately recordings from subjects of that data base, obtaining a Kappa coefficient of 0.74 and an accuracy of 0.82 when just using grown up subjects and a Kappa of 0.77 and accuracy of 0.84 with only children. However, when testing these models on subjects of different age from the ones in the training set the level of performance decreased significantly. On the contrary, the mixed model does succeed when classifying recordings from both age ranges, obtaining an accuracy of 0.81 and a Kappa of 0.75 in the classification of a test group formed by the same number of adults and children. These results support the need to consider subjects of different ages when developing methods for the automatic detection of sleep stages, so the models obtained can adapt to a wider range of patients.Grado en Ingeniería de Tecnologías de Telecomunicació