USSD: Unsupervised Sleep Spindle Detector

Sleep spindles (SSs) appear in electroencephalogram (EEG) recordings during sleep stage N2, and they are usually detected through visual inspection by an expert. Labeling SSs in large datasets is time-consuming and depends on the expert criteria. In this work, we propose an unsupervised SS detector...

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Main Authors: Edgardo Ramirez, Pablo A. Estevez, Martin D. Adams, Claudio A. Perez, Marcelo Garrido Gonzalez, Patricio Peirano
Format: Article
Language:English
Published: IEEE 2025-01-01
Series:IEEE Access
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Online Access:https://ieeexplore.ieee.org/document/10848108/
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author Edgardo Ramirez
Pablo A. Estevez
Martin D. Adams
Claudio A. Perez
Marcelo Garrido Gonzalez
Patricio Peirano
author_facet Edgardo Ramirez
Pablo A. Estevez
Martin D. Adams
Claudio A. Perez
Marcelo Garrido Gonzalez
Patricio Peirano
author_sort Edgardo Ramirez
collection DOAJ
description Sleep spindles (SSs) appear in electroencephalogram (EEG) recordings during sleep stage N2, and they are usually detected through visual inspection by an expert. Labeling SSs in large datasets is time-consuming and depends on the expert criteria. In this work, we propose an unsupervised SS detector based on dictionary learning called the Unsupervised Sleep Spindle Detector (USSD). The proposed detector learns prototype SSs of different lengths (called atoms). An unsupervised adaptive threshold method based on the distribution of the automatically detected SS lengths is developed, which allows the adaptation of the USSD algorithm to different datasets in an unsupervised way. For each detection, the USSD estimates the probability of being an SS. The USSD performances on the labeled MASS-SS2 and INTA-UCH datasets yield F1-scores of <inline-formula> <tex-math notation="LaTeX">$0.72 \pm 0.02$ </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">$0.72 \pm 0.04$ </tex-math></inline-formula>, respectively. The USSD outperforms the A7 and LUNA detectors, which are traditional unsupervised models. Next, we fine-tune the resulting USSD model with 20% of the labeled MASS-SS2 and INTA-UCH datasets, achieving F1 scores of <inline-formula> <tex-math notation="LaTeX">$0.78 \pm 0.06$ </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">$0.75 \pm 0.05$ </tex-math></inline-formula>, respectively. In addition, the SSs detected by USSD on the unlabeled CAP dataset are used to pre-train a supervised deep learning method, which after fine-tuning with 20% of the MODA dataset, reaches an F1-score of <inline-formula> <tex-math notation="LaTeX">$0.81 \pm 0.02$ </tex-math></inline-formula>.
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issn 2169-3536
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spelling doaj-art-660ba8cd69e74e88afdf5130348d37712025-01-31T00:01:30ZengIEEEIEEE Access2169-35362025-01-0113186441865910.1109/ACCESS.2025.353253610848108USSD: Unsupervised Sleep Spindle DetectorEdgardo Ramirez0https://orcid.org/0009-0004-2862-180XPablo A. Estevez1https://orcid.org/0000-0001-9164-4722Martin D. Adams2https://orcid.org/0000-0002-1085-0506Claudio A. Perez3https://orcid.org/0000-0002-5484-4159Marcelo Garrido Gonzalez4https://orcid.org/0000-0002-6027-3735Patricio Peirano5https://orcid.org/0000-0002-4387-3982Department of Electrical Engineering, University of Chile, Santiago, ChileDepartment of Electrical Engineering, University of Chile, Santiago, ChileDepartment of Electrical Engineering, University of Chile, Santiago, ChileDepartment of Electrical Engineering, University of Chile, Santiago, ChileSleep Laboratory, Institute of Nutrition and Food Technology, University of Chile, Santiago, ChileSleep Laboratory, Institute of Nutrition and Food Technology, University of Chile, Santiago, ChileSleep spindles (SSs) appear in electroencephalogram (EEG) recordings during sleep stage N2, and they are usually detected through visual inspection by an expert. Labeling SSs in large datasets is time-consuming and depends on the expert criteria. In this work, we propose an unsupervised SS detector based on dictionary learning called the Unsupervised Sleep Spindle Detector (USSD). The proposed detector learns prototype SSs of different lengths (called atoms). An unsupervised adaptive threshold method based on the distribution of the automatically detected SS lengths is developed, which allows the adaptation of the USSD algorithm to different datasets in an unsupervised way. For each detection, the USSD estimates the probability of being an SS. The USSD performances on the labeled MASS-SS2 and INTA-UCH datasets yield F1-scores of <inline-formula> <tex-math notation="LaTeX">$0.72 \pm 0.02$ </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">$0.72 \pm 0.04$ </tex-math></inline-formula>, respectively. The USSD outperforms the A7 and LUNA detectors, which are traditional unsupervised models. Next, we fine-tune the resulting USSD model with 20% of the labeled MASS-SS2 and INTA-UCH datasets, achieving F1 scores of <inline-formula> <tex-math notation="LaTeX">$0.78 \pm 0.06$ </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">$0.75 \pm 0.05$ </tex-math></inline-formula>, respectively. In addition, the SSs detected by USSD on the unlabeled CAP dataset are used to pre-train a supervised deep learning method, which after fine-tuning with 20% of the MODA dataset, reaches an F1-score of <inline-formula> <tex-math notation="LaTeX">$0.81 \pm 0.02$ </tex-math></inline-formula>.https://ieeexplore.ieee.org/document/10848108/EEGsleep spindleunsupervised learningdictionary learning
spellingShingle Edgardo Ramirez
Pablo A. Estevez
Martin D. Adams
Claudio A. Perez
Marcelo Garrido Gonzalez
Patricio Peirano
USSD: Unsupervised Sleep Spindle Detector
IEEE Access
EEG
sleep spindle
unsupervised learning
dictionary learning
title USSD: Unsupervised Sleep Spindle Detector
title_full USSD: Unsupervised Sleep Spindle Detector
title_fullStr USSD: Unsupervised Sleep Spindle Detector
title_full_unstemmed USSD: Unsupervised Sleep Spindle Detector
title_short USSD: Unsupervised Sleep Spindle Detector
title_sort ussd unsupervised sleep spindle detector
topic EEG
sleep spindle
unsupervised learning
dictionary learning
url https://ieeexplore.ieee.org/document/10848108/
work_keys_str_mv AT edgardoramirez ussdunsupervisedsleepspindledetector
AT pabloaestevez ussdunsupervisedsleepspindledetector
AT martindadams ussdunsupervisedsleepspindledetector
AT claudioaperez ussdunsupervisedsleepspindledetector
AT marcelogarridogonzalez ussdunsupervisedsleepspindledetector
AT patriciopeirano ussdunsupervisedsleepspindledetector