Pee now! NOW, I said! In a huge magnet. While we watch.

Photo credit: Free clipart from www.cliparthut.com
Photo credit: Free clipart from http://www.cliparthut.com

Like many studies that fill in unknown gaps in the body of knowledge, the paper below may not attract attention, except from the people in their narrow field. So let’s give it a little attention.

Michels et al. (2015) sought to map out the brain network underlying the control of urination using the fMRI. They got 22 healthy adult males and they gave them furosemide, which is a diuretic, and then asked them to drink as much water as they want until they need to urinate. During this, “a condom catheter was attached to the penis of each subject” (p. 3370), to monitor the urine flow while in scanner. Then the testing would not start, oh no. The subjects were then submitted to an ultrasound to make sure the bladder was full. Then they were asked again how much they really needed to go pee. Then they go in the scanner in a supine position, where they are told to wait, then to imagine the starting of urination (but don’t pee just yet!), and finally, finally allowed to urinate. But then, cruelly, told to stop only 3 second into the act. And then the scanner cycle would repeat. Their champion peers (I cannot avoid the pun, I’m sorry) managed to pee 15 times in the scanner. I wonder how many subjects peed sans cue… (authors don’t mention that).

Fig. 1 from Michels et al. (2015) depicting the fMRI scan paradigm, which consisted of 2 randomly alternating blocks.
Fig. 1 from Michels et al. (2015) depicting the fMRI scan paradigm, which consisted of 2 randomly alternating blocks. SDV = strong desire to void.

Amazingly, under these conditions, there were seven men who could not urinate in the scanner. Authors call these non-voiders, or, as we commonly know them, the shy bladders or the bashful kidneys. Not surprisingly, non-voiders had lower activity in the pontine micturition center (PMC), a brain area, which, as its name implies, is responsible for urination. Also not surprisingly – for me at least, the authors find this interesting -, the non-voiders showed increased activity in the anterior midcingulate cortex (aMCC), which is an area involved in control. I guess you need some steely control to not pee after all that. The aMCC inhibits the urination-facilitation brain regions, such as the PMC.

Anyway, the main finding of the study is a detailed map of micturition supraspinal mechanisms, which consists of a slew of structures, each with its own function. I had never known how complicated peeing and not-peeing are until I read this paper. Jokes and cringes aside, this study is a welcome addition to understanding how we control our bodily functions and where to start looking when this control fails, shedding new light on the interplay between reflex and control.

Reference: Michels, L., Blok, B. F., Gregorini, F., Kurz, M., Schurch, B., Kessler, T. M., Kollias, S., & Mehnert, U. (October 2015, Epub Jun 26 2014). Supraspinal Control of Urine Storage and Micturition in Men-An fMRI Study. Cerebral Cortex, 25(10): 3369-80. doi: 10.1093/cercor/bhu140. Article | FREE FULLTEXT PDF

By Neuronicus, 1 October 2015

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