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Updated: October 25, 2026
In no case, however, are either the frontal or the temporal sulci the earliest. As a rule the occipito-parietal is the earlier of the two. At the latter part of this period, another sulcus, the "posterio-parietal," or "Fissure of Rolando" is developed, and it is followed, in the course of the sixth month, by the other principal sulci of the frontal, parietal, temporal and occipital lobes.