运动想象中区域去同步的有序起始与运动类别可判别性的转变

Objective. Motor imagery recruits a distributed network whose components and large-scale organization are well characterized. The temporal order in which those components are engaged is not: the latency at which each region begins to desynchronize within a trial has not been compared statistically in the healthy brain, and the interval in which movement-specific information 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. Approach. Two independent public datasets were analysed under a matched pipeline of causal filtering, ocular regression and current source density: Weibo2014 as the internal dataset and BCI Competition IV dataset 2a as the external one. Onset was compared across regions under nine definition-by-threshold combinations, and the time course of class-discriminative information was obtained by time-resolved decoding and modelled with and without a transition. Main results. 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 removing 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 of both datasets and fell at or after it in nearly all, although the two were not shown equivalent at the resolution of the decoding grid. Significance. 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 that information becomes available and placing the analysis interval for imagery decoding on a measured rather than a conventional basis.