The document discusses automatic sleep stage classification from polysomnography (PSG) data using deep learning methods. PSG data contains multimodal time series signals including electroencephalography (EEG), electrooculography (EOG), and electromyography (EMG). The objective is to learn a function that can classify each time point into a sleep stage (awake, REM, stage 1, stage 2, etc.) using the raw PSG signals as input. Deep neural networks have shown promising results on this task compared to traditional machine learning and signal processing methods. The document reviews recent literature on using convolutional neural networks and other deep learning approaches for sleep stage classification from EEG data.