Huttenlocher P R, de Courten C
Hum Neurobiol. 1987;6(1):1-9.
Synaptic density in human striate cortex was determined at various ages, utilizing a computer assisted method. Simultaneous measurement of total volume of striate cortex made it possible to estimate total number of synapses. Synaptogenesis in human striate cortex was found to be most rapid between ages 2-4 months, a time which also is critical for the development of function in visual cortex of the infant. Synapse elimination occurred subsequently with loss of about 40% of synapses between ages 8 months and 11 years. Synapse numbers were stable in adults, except for a slightly lower value in a single brain at age 71 years. Analysis by individual cortical layers showed similar age related changes in all strata of striate cortex, except for somewhat later synaptogenesis in cortical layers V and VI. Total volume of striate cortex reached adult size remarkably early, at about age 4 months. The findings support the hypothesis that exuberant synaptic connections are an anatomical substrate for plasticity in developing cerebral cortex.
利用计算机辅助方法测定了不同年龄段人类纹状皮质中的突触密度。同时测量纹状皮质的总体积，从而能够估算突触的总数。发现人类纹状皮质中的突触发生在2至4个月大时最为迅速，这一时期对婴儿视觉皮质功能的发育也至关重要。随后发生突触消除，在8个月至11岁之间约40%的突触丧失。成年人的突触数量稳定，71岁时单个大脑中的突触数量略低除外。按皮质各层进行分析表明，除了V层和VI层的突触发生稍晚外，纹状皮质所有层中都有类似的年龄相关变化。纹状皮质的总体积在约4个月大时就显著达到成人大小。这些发现支持了这样一种假说，即丰富的突触连接是发育中大脑皮质可塑性的解剖学基础。
