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 -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性优势。通过功能磁共振成像（fMRI）对人类这种执行功能的神经基础进行了深入研究，结果表明左下额皮质（IFC）和左下顶叶（IPL）至关重要。在这里，我们通过磁共振波谱法测量的γ-氨基丁酸（GABA+）和谷氨酸+谷氨酰胺（Glx）研究了在认知灵活性任务期间这些区域的抑制-兴奋平衡及其与表现水平和局部的关系。 40 名年轻人（18-35 岁；26 名女性）和 40 名老年人（18-35 岁；21 名女性）的任务诱导血氧水平依赖性（BOLD）反应。由于 IFC 和 IPL 是紧密相连的区域，我们还检查了与其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 中代谢调节的方向相关，在年轻人和老年人中具有相反的模式。个体抑制-兴奋平衡调节与 IPL 中的局部 BOLD 反应呈反比关系。最后，IPL 中抑制-兴奋平衡的调节仅在老年人中与全脑效应相关。这些发现显示了年轻人和老年人认知灵活性背后的代谢机制的差异及其与表现水平和大胆反应的关系。这种代谢差异可能在衰老过程中的执行功能，特别是认知灵活性中发挥作用。