title: Possible influences of exercise-intensity-dependent increases in non-cortical hemodynamic variables on NIRS-based neuroimaging analysis during cognitive tasks: Technical note.
abstract: OBJECTIVE
  Functional near-infrared spectroscopy (fNIRS) provides functional imaging of cortical activations by measuring regional oxy- and deoxy-hemoglobin (Hb) changes in the forehead during a cognitive task. There are, however, potential problems regarding NIRS signal contamination by non-cortical hemodynamic (NCH) variables such as skin blood flow, middle cerebral artery blood flow, and heart rate (HR), which are further complicated during acute exercise. It is thus necessary to determine the appropriate post-exercise timing that allows for valid NIRS assessment during a task without any increase in NCH variables. Here, we monitored post-exercise changes in NCH parameters with different intensities of exercise.
  
  
  METHODS
  Fourteen healthy young participants cycled 30, 50 and 70% of their peak oxygen uptake (Vo2peak) for 10 min per intensity, each on different days. Changes in skin blood flow velocity (SBFv), middle cerebral artery mean blood velocity (MCA V mean) and HR were monitored before, during, and after the exercise.
  
  
  RESULTS
  Post-exercise levels of both SBFv and HR in contrast to MCA V mean remained high compared to basal levels and the times taken to return to baseline levels for both parameters were delayed (2-8 min after exercise), depending upon exercise intensity.
  
  
  CONCLUSIONS
  These results indicate that the delayed clearance of NCH variables of up to 8 min into the post-exercise phase may contaminate NIRS measurements, and could be a limitation of NIRS-based neuroimaging studies.
authors: Laboratory of Exercise Biochemistry and Neuroendocrinology, Faculty of Health and Sport Sciences, University of Tsukuba, Ibaraki, Japan.
authors: Kyeongho
authors: K
authors: Byun
authors: Laboratory of Exercise Biochemistry and Neuroendocrinology, Faculty of Health and Sport Sciences, University of Tsukuba, Ibaraki, Japan.
authors: Kazuki
authors: K
authors: Hyodo
authors: Laboratory of Exercise Biochemistry and Neuroendocrinology, Faculty of Health and Sport Sciences, University of Tsukuba, Ibaraki, Japan.
authors: Kazuya
authors: K
authors: Suwabe
authors: Department of Physiology, Gdansk University of Physical Education and Sport, Gdansk, Poland.
authors: Sylwester
authors: S
authors: Kujach
authors: Department of Health and Nutrition, Yonezawa Nutrition University of Yamagata Prefecture, Yamagata, Japan.
authors: Morimasa
authors: M
authors: Kato
authors: Laboratory of Exercise Biochemistry and Neuroendocrinology, Faculty of Health and Sport Sciences, University of Tsukuba, Ibaraki, Japan.
authors: Hideaki
authors: H
authors: Soya
keywords: NIRS; exercise intensity; non-cortical hemodynamic changes; post-exercise phase