Neuromagnetic signatures of the spatiotemporal transformation for manual pointing

Movement planning involves transforming the sensory signals into a command in motor coordinates. Surprisingly, the real-time dynamics of sensorimotor transformations at the whole brain level remain unknown, in part due to the spatiotemporal limitations of fMRI and neurophysiological recordings. Here, we used magnetoencephalography (MEG) during pro-/anti-wrist pointing to determine (1) the cortical areas involved in transforming visual signals into appropriate hand motor commands, and (2) how this transformation occurs in real time, both within and across the regions involved. We computed sensory, motor, and sensorimotor indices in 16 bilateral brain regions for direction coding based on hemispherically lateralized de/synchronization in the α (7–15 Hz) and β (15–35 Hz) bands. We found a visuomotor progression, from pure sensory codes in ‘early’ occipital-parietal areas, to a temporal transition from sensory to motor coding in the majority of parietal-frontal sensorimotor areas, to a pure motor code, in both the α and β bands. Further, the timing of these transformations revealed a top-down pro/anti cue influence that propagated ‘backwards’ from frontal through posterior cortical areas. These data directly demonstrate a progressive, real-time transformation both within and across the entire occipital-parietal-frontal network that follows specific rules of spatial distribution and temporal order. •A unifying picture of the spatiotemporal transformations from vision to action in real time at the regional and whole brain level is missing.•We use magnetoencephalography (MEG) in a pro-/anti-pointing task.•Our data support an early feed-forward occipital-to-frontal sweep of visual signals and motor coding first appeared in frontal motor areas.•This was followed by a gradual frontal-to-parietal backward wave of transitions from sensory to motor coding.•Thus, the visuomotor transformation for pointing occurred gradually across cortical space and time.