Age-related differences in the within-session trainability of hemodynamic parameters: a near-infrared spectroscopy–based neurofeedback study

Neurofeedback studies revealed that the hemodynamic response as assessed with near-infrared spectroscopy (NIRS) can be voluntarily modulated. However, the hemodynamic response generally changes with age, and it remains unclear whether age-related differences in the hemodynamic response affect the trainability of brain signals. In the present study, N = 24 healthy young adults (mean age: 23 years; age range: 21-28 years) and N = 19 healthy older individuals (mean age: 69 years; age range: 60-84 years) performed one NIRS-based neurofeedback session. Half of all participants either tried to increase deoxygenated hemoglobin (deoxy-Hb) or decrease oxygenated hemoglobin over the inferior frontal gyrus (IFG) during imagery of swallowing movements. In addition, the hemodynamic response during motor imagery and execution of swallowing without real-time feedback was compared between groups. Young and older adults showed an opposite NIRS signal change during motor imagery, probably indicating a reduced movement inhibition ability in older individuals. Age-related differences in the trainability of the hemodynamic response during neurofeedback training were observed, too. Young participants were able to decrease oxygenated hemoglobin and increase deoxy-Hb over the bilateral IFG, whereas older participants were mainly able to increase deoxy-Hb over the left IFG. Our results provide evidence of age-related differences in the within-session trainability of the hemodynamic response as assessed with NIRS and have an impact on the application of NIRS-based real-time feedback.