Near Infrared Spectroscopy study of the central nervous activity during artificial changes in bladder sensation in men

Objectives: To investigate the regional specificity of multi-channel near infrared spectroscopy (NIRS) on the detection of urination-related cortical activation in healthy men. Methods: Frontal lobe blood flow was measured non-invasively in 20 resting subjects using NIRS before and after micturition. The relative concentrations of oxyhemoglobin were recorded over the frontal lobe during artificial changes in bladder sensation with a 52-channel NIRS machine. An increase in oxyhemoglobin represented locally increased blood flow. In artificially induced bladder sensation (desire to void), the lower abdomen of each participant was pressed by the examiner's hand to keep each participant feeling the desire to void for 5 s. Each participant received this series of tasks three times before and after urination. Activated concentrations calculated by contrast of subtracting the two different conditions were designed to disclose the brain areas that are involved during artificial changes in bladder sensation. The measurements were repeatedly carried out for each subject on different days to reveal the reproducibility and intra-individual variability of the results. Results: Cerebral responses during artificial changes in bladder sensation were bilaterally associated with increased levels of oxyhemoglobin in the frontal area. Oxyhemoglobin increases during the compression maneuver were significantly larger than those during an empty bladder in several bilateral frontal channels (P < 0.05). Conclusions: Frontal regions were activated during artificial changes in bladder sensation before micturition using a 52-channel NIRS machine.