engleski

Distribution of synapses in the human cingulate cortex during the formation of the sublate zone

The formation of the subplate (SP) through the transformation of the deep cortical plate (CP) is poorly understood event. The presence of synapses in the cell-loose CP (the "second" CP) at 13 weeks of gestation (W) transiently distinguishes that lamina from synapse-free, cell-dense CP proper, indicating the formation of the SP (Kostovic & Rakic, J Comp Neurol 1990). In present paper, we correlate E. M. and Nissl to study SP formation and synapse distribution in postmortem human cingulate cortex (CC) at 13-15 W. We found that by 15 W ventral, mesocortical part of CC shows incomplete transformation ('bilamination') into the SP and does not undergo secondary consolidation of CP, but has enlarged marginal zone (MZ). Dorsal, neocortical part of CC shows complete transformation of the "second" CP by 15 W (1.5 weeks later than dorsolateral neocortex) and undergoes secondary consolidation. In both ventral and dorsal CC, synapses were found in the deep (loose) part of CP and in the SP and were numerous in the MZ. In the dorsal neocortical part of CC, synapses were found throughout the second lamina of CP (SP in formation) while in the ventral CC the presence of synapses is restricted to the deepest part of CP. In conclusion, the CC shows precocious development of synapses in the marginal zone but lags behind the dorsolateral neocortex in synaptogenesis within the deep cortex (second CP and SP). Ventral, mesocortical part of CC maintains synapses within the incompletely laminated CP, thus being different from the neocortex in which synapses do not appear in the consolidated CP before 24 W. Finally, we found that the subplate formation stage is related to the specific stage in development of deep cortical circuitry, which is characteristic for a given regional type of the cortex.

development; CNS; synaptogenesis

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