Ordered onset of regional desynchronization and a transition in movement-class discriminability during cue-paced...

Motor imagery recruits a distributed sensorimotor network, yet the order in which its regions are engaged has not been tested statistically within the healthy brain, and the interval in which information about the imagined movement appears remains unidentified. Early post-cue classification peaks have been attributed to visually induced orienting rather than to imagery, an inference drawn from a condition contrast rather than direct measurement.Two independent public datasets were analysed under a matched pipeline of causal filtering, ocular regression and current source density: Weibo2014 as the primary dataset and BCI Competition IV dataset 2a for validation. Mu and beta desynchronization onset was ordered across cortex, from occipital through sensorimotor and midline pre-supplementary motor area to lateral prefrontal. The ordering held under all nine onset criteria examined, under channel-count matching and within-trial pairing, and after removal of the sensorimotor component. Class-discriminative information rose most steeply between 0.60 and 0.75 s and saturated within a further 0.3 s. This transition lay closer to sensorimotor onset than to cue presentation in every participant and fell at or after that onset in nearly all of them, although the two were not shown equivalent at the resolution of the decoding grid. Windows centred on each region's own onset classified equivalently to reassigned windows, so the ordering serves as a temporal landmark rather than a decodable feature, locating the interval in which information about the imagined movement becomes available.