Figure 1.

Hypothesized cortical system and experimental paradigm. (A) Estimation of the pericentral (green shade), frontoparietal (blue) and perisylvian-occipital (red) divisions of the cortex postulated to support handwriting in the left hemisphere (inset displays the dorsal medial view). Colored dots indicate the reference points derived from neuroimaging literature (as cited in the Methods). Dashed lines indicate the central and intraparietal sulci. dPM; IFC, inferior frontal cortex; IOTC, inferior occipitotemporal cortex; IPL, inferior parietal lobe; IPS, intraparietal sulcus; POper, parietal operculum; SMA; SMC, primary sensorimotor cortex; SPL, superior parietal lobe; STC, superior temporal cortex; vPM. (B) Schematic illustration of the hypothetical network system for handwriting consisting of the pericentral (hand coordination), frontoparietal (core working memory), and perisylvian-occipital (audiovisual language) subsystems. Nodal regions (circles) interact through coherent signaling (bidirectional arrows) within and between the subsystems. The pericentral module forms a control loop with the arm musculature. (C) In a delayed dictation-to-writing/audio cue-to-movement paradigm, the subjects first memorized sentences or auditory pattern cues and, right after, produced corresponding movements. The tasks included RW; LW; PD; and repetitive LD where nonsense scramble stimuli did not offer guidance for the movement. Timeline of a single experimental trial is presented under the task descriptions (WS, warning signal; GO, signal for starting the movement). (An example Finnish sentence [in RW] translates as “The herd seeks shelter”.) The emphasis of task-associated motor and cognitive processes in each task is depicted below.