"Another histological study of 12 specimens found that afferents from unspecified thalamic regions reached the developing prefrontal cortex in 1 preterm neonate of 27 weeks’ developmental age, concluding that thalamic fibers begin entering the cortex between 26 and 28 weeks’ developmental age (28 and 30 weeks’ gestational age). A different study found that thalamic afferents had not reached the somatosensory cortical plate by 22 weeks’ developmental age (24 weeks’ gestational age). By 24 weeks’ developmental age (26 weeks’ gestational age), the density of cortical plate synapses increased, although these were not necessarily from thalamic afferents. Based on these studies, direct thalamocortical fibers that are not specific for pain begin to emerge between 21 and 28 weeks’ developmental age (23 and 30 weeks’ gestational age)."