Biomedical Optics Research Laboratory, Division of Neonatology, University Hospital Zurich, Zurich, 8091, Switzerland.
Institute of Complementary Medicine, University of Bern, Imhoof-Pavillon, Inselspital, 3010, Bern, Switzerland.
Adv Exp Med Biol. 2013;789:81-87. doi: 10.1007/978-1-4614-7411-1_12.
The aim of the present study was (i) to investigate the effect of inner speech on cerebral hemodynamics and oxygenation, and (ii) to analyze if these changes could be the result of alternations of the arterial carbon dioxide pressure (PaCO2). To this end, in seven adult volunteers, we measured changes of cerebral absolute [O2Hb], [HHb], [tHb] concentrations and tissue oxygen saturation (StO2) (over the left and right anterior prefrontal cortex (PFC)), as well as changes in end-tidal CO2 (PETCO2), a reliable and accurate estimate of PaCO2. Each subject performed three different tasks (inner recitation of hexameter (IRH) or prose (IRP) verses) and a control task (mental arithmetic (MA)) on different days according to a randomized crossover design. Statistical analysis was applied to the differences between pre-baseline, two tasks, and four post-baseline periods. The two brain hemispheres and three tasks were tested separately. During the tasks, we found (i) PETCO2 decreased significantly (p < 0.05) during the IRH ( ~ 3 mmHg) and MA ( ~ 0.5 mmHg) task. (ii) [O2Hb] and StO2 decreased significantly during IRH ( ~ 1.5 μM; ~ 2 %), IRP ( ~ 1 μM; ~ 1.5 %), and MA ( ~ 1 μM; ~ 1.5 %) tasks. During the post-baseline period, [O2Hb] and [tHb] of the left PFC decreased significantly after the IRP and MA task ( ~ 1 μM and ~ 2 μM, respectively). In conclusion, the study showed that inner speech affects PaCO2, probably due to changes in respiration. Although a decrease in PaCO2 is causing cerebral vasoconstriction and could potentially explain the decreases of [O2Hb] and StO2 during inner speech, the changes in PaCO2 were significantly different between the three tasks (no change in PaCO2 for MA) but led to very similar changes in [O2Hb] and StO2. Thus, the cerebral changes cannot solely be explained by PaCO2.
(i) 探究内言语对脑血流动力学和氧合的影响；(ii) 分析这些变化是否是动脉二氧化碳分压（PaCO2）改变的结果。为此，我们在七名成年志愿者中，测量了左、右前额叶皮质（PFC）脑区绝对 [O2Hb]、[HHb]、[tHb] 浓度和组织氧饱和度（StO2）的变化，以及呼气末二氧化碳（PETCO2）的变化，后者是 PaCO2 的可靠且准确的估计值。每位受试者根据随机交叉设计，在不同的日子里分别进行三项不同的任务（内六步格诗（IRH）或散文（IRP）诵读，以及心算（MA））和一项对照任务。采用统计学方法分析了预基线、两个任务和四个后基线期间的差异。分别对两个大脑半球和三个任务进行了测试。在任务期间，我们发现：(i) 在 IRH（3mmHg）和 MA（0.5mmHg）任务期间，PETCO2 显著下降（p<0.05）。(ii) 在 IRH（1.5μM；2%）、IRP（1μM；1.5%）和 MA（1μM；1.5%）任务期间，[O2Hb]和 StO2 显著下降。在后基线期间，IRP 和 MA 任务后左 PFC 的 [O2Hb]和 [tHb] 显著下降（分别为1μM 和2μM）。总之，本研究表明内言语会影响 PaCO2，这可能是由于呼吸的改变。虽然 PaCO2 的下降会导致脑血管收缩，可能可以解释内言语时 [O2Hb]和 StO2 的下降，但在三个任务之间 PaCO2 的变化差异显著（MA 时 PaCO2 无变化），但却导致了非常相似的 [O2Hb]和 StO2 变化。因此，脑区的变化不能仅用 PaCO2 来解释。
