CHANGES IN VOLUME, SURFACE ESTIMATE, 3-DIMENSIONAL SHAPE AND TOTAL NUMBER OF NEURONS OF THE HUMAN PRIMARY VISUAL-CORTEX FROM MIDGESTATION UNTIL OLD-AGE

Macroscopic features such as volume, surface estimate, thickness and c audorostral length of the human primary visual cortex (Brodman's area 17) of 46 human brains between midgestation and 93 years were studied by means of camera lucida drawings from serial frontal sections. Indiv idual values were best fitted by a logistic function from midgestation to adulthood and by a regression line between adulthood and old age. Allometric functions were calculated to study developmental relationsh ips between all the features. The three-dimensional shape of area 17 w as also reconstructed from the serial sections in 15 cases and correla ted with the sequence of morphological events. The sulcal pattern of a rea 17 begins to develop around 21 weeks of gestation but remains rath er simple until birth, while it becomes more convoluted, particularly in the caudal part, during the postnatal period. Until birth, a large increase in cortical thickness (about 83% of its mean adult value) and caudorostral length (69%) produces a moderate increase in cortical vo lume (31%) and surface estimate (40%) of area 17. After birth, the cor tical volume and surface undergo their maximum growth rate, in spite o f a rather small increase in cortical thickness and caudorostral lengt h. This is due to the development of the pattern of gyrification withi n and around the calcarine fissure. All macroscopic features have reac hed the mean adult value by the end of the first postnatal year. With aging, the only features to undergo significant regression are the cor tical surface estimate and the caudorostral length. The total number o f neurons in area 17 shows great interindividual variability at all ag es. Mo decrease in the postnatal period or in aging could be demonstra ted.