Human brain region response to distention or cold stimulation of the bladder: a positron emission tomography study

Several kinds of perceptions, including distention and coldness, arise from the bladder. Information on bladder fullness conveyed by mechanoreceptors within the bladder wall contributes to the basic micturition reflex via the bulbospinal reflex pathway, whereas cold stimulation of the bladder is processed differently. To elucidate the human brain mechanisms of voluntary urine storage and bladder cold perception we performed positron emission tomography scanning to examine brain regions activated by bladder distention or cold stimulation.

A total of 17 right-handed healthy male volunteers were catheterized via the urethra for bladder infusion. Subjects were divided into 2 groups for 2 types of positron emission tomography, namely the bladder distention group-11 who were 24 to 41 years old and the intravesical ice water group-6 who were 24 to 38 years old. Data were analyzed by the statistical parametric mapping procedure.

Significant brain activation during maximum urine storage (bladder distention) were found in the pons, midbrain periaqueductal gray, anterior insula, putamen, thalamus and anterior cingulate gyrus. On the other hand, intravesical ice water instillation significantly activated several regions in frontal and parietal lobes, amygdala-hippocampus area and crus cerebri ventral border. Distribution of the activated regions after intravesical instillation of ice water overlapped none of those observed after bladder distention.

Our data show that the brainstem as well as more rostral regions are involved in voluntary urine storage and these regions are functionally separated from those associated with bladder cold perception in healthy individuals.