Abnormal theta- and gamma-band cortical activities during visuospatial attention in idiopathic REM sleep behavior disorder patients.

Purpose: Idiopathic rapid eye movement (REM) sleep behavior disorder (iRBD) is a sleep disorder considered to be a prodromal stage of neurodegeneration disease and is often accompanied by cognitive impairments. The purpose of this study was to investigate spatiotemporal characteristics of abnormal oscillatory cortical activity associated with dysfunction of visuospatial attention in iRBD based on an explainable machine learning approach. Methods: EEGs were recorded from 49 iRBD patients and 49 normal controls while they were performing Posner's cueing task and transformed to cortical current density time-series. Spectral cortical activities for four frequency bands (theta, alpha, beta, and gamma) were estimated, and then converted to three-dimensional (3D) spatiotemporal data. A pattern classifier based on 3D convolutional neural network was devised to discriminate the cortical activities of iRBD patients and those of normal controls. Results: The location, time, and frequency which characterize the difference between the patients and normal controls, thereby deemed to be associated with cognitive impairment due to the iRBD, were identified by finding the input nodes which were most critical to the classifier's decision. Conclusion: Our results suggest that theta- and gamma-band activities in parietal and occipital regions, which may underlie efficient visuospatial processing and attentional reallocation, are impaired in iRBD patients, resulting in poor visuospatial attention performance. Supplementary Information: The online version contains supplementary material available at 10.1007/s13534-025-00493-5.