The effect of inner speech on arterial CO2 and cerebral hemodynamics and oxygenation: a functional NIRS study

Scholkmann, Felix; Wolf, Martin; Wolf, Ursula (2013). The effect of inner speech on arterial CO2 and cerebral hemodynamics and oxygenation: a functional NIRS study. In: van Huffel, Sabine; Naulaers, Gunnar; Caicedo, Alexander; Bruley, Duane F.; Harrison, David K. (eds.) Oxygen Transport to Tissue XXXV. Part II. Advances in Experimental Medicine and Biology: Vol. 789 (pp. 81-87). Springer 10.1007/978-1-4614-7411-1_12

Full text not available from this repository. (Request a copy)

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.

Item Type:

Book Section (Book Chapter)


04 Faculty of Medicine > Medical Education > Institute of Complementary and Integrative Medicine (IKIM)

UniBE Contributor:

Scholkmann, Felix Vishnu, Wolf, Ursula


600 Technology > 610 Medicine & health






Advances in Experimental Medicine and Biology






Sabine Klein

Date Deposited:

13 May 2014 10:35

Last Modified:

02 Mar 2023 23:25

Publisher DOI:


PubMed ID:



Actions (login required)

Edit item Edit item
Provide Feedback