Movement Control and Neuroplasticity Research Group, Biomedical Sciences, KU Leuven, Leuven 3001, Belgium.
Leuven Brain Institute, KU Leuven, Leuven 3000, Belgium.
J Neurosci. 2024 Sep 4;44(36):e0355242024. doi: 10.1523/JNEUROSCI.0355-24.2024.
Cognitive flexibility represents the capacity to switch among different mental schemes, providing an adaptive advantage to a changing environment. The neural underpinnings of this executive function have been deeply studied in humans through fMRI, showing that the left inferior frontal cortex (IFC) and the left inferior parietal lobule (IPL) are crucial. Here, we investigated the inhibitory-excitatory balance in these regions by means of γ-aminobutyric acid (GABA+) and glutamate + glutamine (Glx), measured with magnetic resonance spectroscopy, during a cognitive flexibility task and its relationship with the performance level and the local task-induced blood oxygenation level-dependent (BOLD) response in 40 young (18-35 years; 26 female) and 40 older (18-35 years; 21 female) human adults. As the IFC and the IPL are richly connected regions, we also examined whole-brain effects associated with their local metabolic activity. Results did not show absolute metabolic modulations associated with flexibility performance, but the performance level was related to the direction of metabolic modulation in the IPL with opposite patterns in young and older individuals. The individual inhibitory-excitatory balance modulation showed an inverse relationship with the local BOLD response in the IPL. Finally, the modulation of inhibitory-excitatory balance in IPL was related to whole-brain effects only in older individuals. These findings show disparities in the metabolic mechanisms underlying cognitive flexibility in young and older adults and their association with the performance level and BOLD response. Such metabolic differences are likely to play a role in executive functioning during aging and specifically in cognitive flexibility.
认知灵活性代表了在不同心理模式之间切换的能力，为不断变化的环境提供了适应优势。通过 fMRI，人类对这种执行功能的神经基础进行了深入研究，表明左额下回（IFC）和左顶下小叶（IPL）是至关重要的。在这里，我们通过磁共振波谱测量了这些区域的 GABA+和谷氨酸+谷氨酰胺（Glx），以研究抑制-兴奋平衡，在认知灵活性任务及其与表现水平和局部任务诱导的血氧水平依赖（BOLD）反应的关系，研究了 40 名年轻（18-35 岁；26 名女性）和 40 名老年（18-35 岁；21 名女性）成年人大脑。由于 IFC 和 IPL 是富含连接的区域，我们还检查了与它们局部代谢活动相关的全脑效应。结果并未显示与灵活性表现相关的绝对代谢调节，但表现水平与 IPL 中代谢调节的方向有关，年轻和老年个体的模式相反。个体抑制-兴奋平衡的调制与 IPL 中的局部 BOLD 反应呈负相关。最后，IPL 中抑制-兴奋平衡的调制仅与老年个体的全脑效应有关。这些发现表明，年轻和老年成年人认知灵活性的代谢机制存在差异，以及它们与表现水平和 BOLD 反应的关系。这种代谢差异可能在衰老期间的执行功能中发挥作用，特别是在认知灵活性方面。
