TIME IS OF THE ESSENCE - A CONJECTURE THAT HEMISPHERIC-SPECIALIZATION ARISES FROM INTERHEMISPHERIC CONDUCTION DELAY
TIME IS OF THE ESSENCE - A CONJECTURE THAT HEMISPHERIC-SPECIALIZATION ARISES FROM INTERHEMISPHERIC CONDUCTION DELAY
复制标题
DOI：
10.1093/cercor/4.4.331
复制
发表时间：
1994-07-01
期刊：
影响因子：
3.7
通讯作者：
SIMARD, PY
中科院分区：
文献类型：
--
作者：
RINGO, JL;DOTY, RW;SIMARD, PY
Tomasch（1954）和Mrsatiz等（1992）发现人体胼胝体的大部分纤维直径小于1 μ m。Swadlow等人（1980年）的电子显微镜研究以及LaMantia和Rakic（1990年a）对猕猴的详细研究表明，有髓鞘胼胝体轴突的平均大小也小于1 μ m。在人类中，连接颞叶的平均大小的有髓纤维将具有超过25毫秒的单向半球间延迟。因此，精细详细的，时间关键的神经元计算（即，那些使胼胝体承受能力紧张的任务，因此不能仅仅由较大的纤维来处理）将通过更短和更快的半球内回路更快地执行。虽然一次通过连合系统可能会产生可容忍的延迟，但在涉及“结算”的系统中多次通过似乎会慢得令人望而却步。我们认为，这些时间限制将被避免，如果执行每个高分辨率，时间紧迫的任务所需的神经装置被聚集在一个半球。如果处理重叠任务所需的神经组件聚集在一起，这可能会导致大脑半球的专门化。根据预测，大象和鲸目动物等哺乳动物的大大脑也将表现出高度的半球特化。
Tomasch (1954) and Aboitiz et al. (1992) found the majority of the fibers of the human corpus callosum are under 1 mu m in diameter. Electron microscopic studies of Swadlow et al. (1980) and the detailed study of LaMantia and Rakic (1990a) on macaques show the average size of the myelinated callosal axons also to be less than 1 mu m. In man, the average-sized myelinated fiber interconnecting the temporal lobes would have a one-way, interhemispheric delay of over 25 msec. Thus, finely detailed, time-critical neuronal computations (i.e., tasks that strain the capacity of the callosum and hence could not be handled by just the larger fibers) would be performed more quickly via shorter and faster intrahemispheric circuits. While one transit across the commissural system might yield tolerable delays, multiple passes as in a system involving ''settling'' would seem prohibitively slow. We suggest that these temporal limits will be avoided if the neural apparatus necessary to perform each high-resolution, time-critical task is gathered in one hemisphere. If the, presumably overlapping, neural assemblies needed to handle overlapping tasks are clustered together, this would lead to hemispheric specialization. The prediction follows that the large brains of mammals such as elephants and cetaceans will also manifest a high degree of hemispheric specialization.