White and Grey Matter Changes in the Language Network during Healthy Aging

Neural structures change with age but there is no consensus on the exact processes involved. This study tested the hypothesis that white and grey matter in the language network changes during aging according to a “last in, first out” process. The fractional anisotropy (FA) of white matter and cortical thickness of grey matter were measured in 36 participants whose ages ranged from 55 to 79 years. Within the language network, the dorsal pathway connecting the mid-to-posterior superior temporal cortex (STC) and the inferior frontal cortex (IFC) was affected more by aging in both FA and thickness than the other dorsal pathway connecting the STC with the premotor cortex and the ventral pathway connecting the mid-to-anterior STC with the ventral IFC. These results were independently validated in a second group of 20 participants whose ages ranged from 50 to 73 years. The pathway that is most affected during aging matures later than the other two pathways (which are present at birth). The results are interpreted as showing that the neural structures which mature later are affected more than those that mature earlier, supporting the “last in, first out” theory.

神经结构随年龄增长发生重塑，但学界对其背后的确切过程尚未形成统一共识。本研究针对一项假说展开验证：衰老过程中，语言网络内的白质与灰质变化遵循“后进先出（last in, first out）”机制。研究纳入36名年龄介于55至79岁的受试者，对其白质的各向异性分数（fractional anisotropy, FA）以及灰质的皮层厚度进行了检测。在语言网络中，连接中后颞上皮层（superior temporal cortex, STC）与额下回皮层（inferior frontal cortex, IFC）的背侧通路，其FA值与皮层厚度受衰老的影响程度，显著高于另外两条通路：其一为连接STC与运动前皮层的背侧通路，其二为连接中前颞上皮层与腹侧额下回皮层的腹侧通路。上述结果在第二组受试者中得到独立验证，该组共20名受试者，年龄范围为50至73岁。受衰老影响最显著的通路，其成熟时序晚于另外两条于出生时即已存在的通路。研究结果显示，成熟越晚的神经结构，受衰老的影响程度越高，这一发现支持了“后进先出”理论。