Cytoarchitectonic development of the prefrontal cortex in the rat

TLDR

Postnatal development of the rat prefrontal cortex proceeds through three distinct phases. The study aims to describe cytoarchitectonic features that allow early delineation of rat prefrontal cortex subareas from day 6 onward. The authors examined cortical development from day 1 to 18, noting neuronal differentiation and layer formation, the disappearance of the cortical plate by day 6–10, and progressive cytoarchitectonic changes until day 18. Cytoarchitectonic analysis revealed early regional differences at day 1, clear layer IV formation and prefrontal demarcation by day 6, minimal changes during days 18–30, increasing layer ambiguity and variance from days 30–90, and earlier development of the orbital compared to the medial prefrontal cortex.

Abstract

Abstract This paper gives an account of the cytoarchitectonic characteristics that make it possible to delineate, from as early as day 6, different subareas of the prefrontal cortex of the rat. Three phases can be distinguished during postnatal development. The first phase (from day 1 until day 18) is dominated by differentiation of the neurons within the cortical plate and by the formation of the cortical layers. At day 1, regional differences are observed in the cytoarchitecture of the cortical plate which correspond to the future subareas of the prefrontal cortex. The formation of layer IV occurs in the dorsolateral cortex around day 6, and from this age the agranular prefrontal cortex is well demarcated from the other parts of the frontal cortex. Between day 6 and day 10, the cortical plate has disappeared and all cortical layers can be recognized in the prefrontal cortex. Differentiation of the cells within the cortical layers changes the cytoarchitectonic character of the layers through day 18. During the second phase (from day 18 until day 30) little change occurs in the cytoarchitectonic characteristics of the prefrontal subareas. During the third phase (from day 30 until day 90) the delineation of the cortical layers becomes less clear in Nissl‐stained sections, and the individual cytoarchitectonic variance increases. On the basis of cytoarchitectonic criteria it can be concluded that the orbital prefrontal cortex develops earlier than does the medial prefrontal cortex.