Synaptogenesis In Human Cerebral Cortex

Figure 2.3 Changes in the relative densities of synapses in the primary visual cortex (discontinuous line) and prefrontal cortex (continuous line) of human brain as a function of days after conception expressed on a log scale on the abscissae. Phases 3 and 4 are indicated with numbers 3 and 4. (This is a schematic representation of data published in Huttenlocher and Dabholkar, 1997, with permission from the authors and John Wiley and Sons, Inc.)

Figure 2.3 Changes in the relative densities of synapses in the primary visual cortex (discontinuous line) and prefrontal cortex (continuous line) of human brain as a function of days after conception expressed on a log scale on the abscissae. Phases 3 and 4 are indicated with numbers 3 and 4. (This is a schematic representation of data published in Huttenlocher and Dabholkar, 1997, with permission from the authors and John Wiley and Sons, Inc.)

parvalbumin-positive axon cartridges from chandelier cells was observed until puberty, while a short peak of density of dopaminergic varicosities was observed exactly during puberty (Anderson et al., 1995). In the human cerebral cortex, sequential developments of distinct cortical circuits (Burkhalter, Bernardo, and Charles, 1993) most probably correspond to distinct waves of synaptogenesis. These are the first examples of a long list of discrete synaptogenetic events we are just beginning to explore.

All these preliminary studies show that phase 3 is a period of rapid production of all categories of synaptic contacts, even if during the next phases different categories of synapses may display different kinetics in macaque (Anderson et al., 1995; Bourgeois, Goldman-Rakic, and Rakic, 1994; Bourgeois and Rakic, 1993; Ze-cevic, Bourgeois, and Rakic, 1989; Zecevic and Rakic, 1991), mouse (de Felipe et al., 1997), and human (figure 2.3; Huttenlocher and Dabholkar, 1997) cerebral cortices.

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