Cell phones: coming for your brain cells since...well, maybe not.

Feb 23 2011 Published by under Behavioral Neuro, Neuroscience

After however long Sci has been in the blogsphere, I think I've become inured to the near constant babble of breathless science reporting.  Oral contraceptives CHANGE YOUR BRAIN!!  You are yourself...ON HORMONES.  Cell phones cause brain cancer!  TIDAL WAVES of hormones. TSUNAMIS of brain activity!  A veritable STORM SURGE  of wave metaphors have invaded our science reporting, folks.  But then I think, meh, you know, it's just another report from someone who just read an already breathlessly written press release, it'll all work itself out, and I just can't get worked up anymore...I need another latte...

And then I see this kind of thing:

Power-talkers with cell phones glued to their ears may be getting more than conversation.


Do cell phones cause cancer?

We'd all like to know, but unfortunately there's no clear answer — yet.


And then it's coupled with things like "brain metabolism", "brain activity", and my current favorite (emphasis mine):

higher rates of glucose metabolism in the brain can mean a number of things. Yes, tumor cells may gobble up more glucose to fuel their relentless growth, but healthy brain cells need constant replenishment too, to keep up the intricate network of messages and connections that help us think, eat, move and stay alive.


Yeah, it COULD be your greedy TUMOR CELLS gobbling up your BRAIN ENERGY!!!  Or it could be something else!

I feel comforted now. You?

Luckily, most of the reporting was really pretty even handed, but I don't think it's for lack of trying.  Rather it's because...well...the study had very little to report.

But just in case...


Volkow et al. "Effects of Cell Phone Radiofrequency Signal Exposure on Brain Glucose Metabolism" JAMA, 2011.

People are concerned about the effects of cell phones on your brain.  They are also concerned about microwaves effects on your brain (did you know there are people out there who really think microwaves control your MIND?!), the effects of laptops on your balls, the effects of chemicals in your water bottles, and the list goes on.  Many of these things may indeed be of concern.  Man, if technology didn't mean a 15-20 year increase in average life expectancy and a drastic increase in perceived quality of life, what crapola it would be.

I'm being flippant, obviously.  We do tend to make and discover cool things first and figure out they are bad for us later (see Radium for one of my personal favorites).   And it seems like everyone these days owns a cell phone.  And you can't deny that when you've been on them for a while and the little buggers get kind of warm, you start to worry a little.

You may not be wrong to worry.  But the JURY IS STILL OUT.  Despite quotes like these:

Some studies have linked cell phone exposure to an increased risk of brain cancers, but a large study by the World Health Organization was inconclusive.


The current information is no cause for panic.  In fact, the above quote is misleading.  Unless by "a large study by the World Health Organization was inconclusive" they MEAN "a large study be the World Health organization found no correlation".  Inconclusive sounds scarier, I guess.

Anyway, we really DON'T know whether prolonged use of cell phones when applied directly to the ear is bad for you or not.  This study DOES NOT ADDRESS whether prolonged use of cell phones on the ear is bad for you or not.  What it DOES address is whether or not cell phones can in fact change brain activity.

To look at this, they took 47 people, and ran PET studies on them, looking at glucose utilization.  What happens here is that a person is injected (usually, though I think you can actually take it in a drink) with a solution containing a small amount of radioactively marked glucose.  The radioactivity in the molecule will give off gamma rays, detected by a machine.  You can then use the concentration of gamma rays in various areas to suggest where large amounts of glucose are being moved in the brain by cerebral blood flow.  The general idea is that where the blood is going, there goeth the activity.

In this case, they looked at glucose utilization over two days of studies.  The participant would get two cell phones strapped on either ear and hung out in the PET machine for an hour.  On one day (the order was randomized), both cell phones were off.  On the other day, the RIGHT cell phone was ON, and receiving a message, but was on mute so the participant couldn't hear anything (and so you wouldn't see brain activity resulting from what the participant was hearing).  The cell phone was the Samsung Knack Flip phone.

Here's what they got:


This figure shows the radiofrequency field of the antenna of the cell phones.  According to the radiofrequency of the on cell phone looks like it hits the low part of the temporal gyrus the most, with some effects on the orbitofrantal gyrus.

When they ran the PET, this is what they got:


This here is a representative brain image of glucose metabolism during the "off" (right) and "on" (left) cell phone conditions.  What they saw was an increase (in total of about 7%) of glucose metabolism in the orbitofrontal cortex.  No increases in total brain glucose metabolism (7% in one area is too small to affect the glucose metabolism of the brain as a whole).

That's it.  That's ALL.  What can we infer from this?  That the presence of an "on" cell phone increases glucose metabolism on the side of the orbitofrontal cortex where it is held.  The authors hypothesize that the electrical potentials from the cell phones may be affecting things like membrane potentials in this area, possibly making it more active.  It IS an affect on brain metabolic activity in that area.

What does that mean?  Dang if I know, and dang if they know either.  They do note that there's an increase in brain metabolic activity, but no one has ANY idea if this could have anything to do with cancer.

I think this is an interesting study, and I think, like the authors, that this should make people want to learn more.  But I also have some questions.

1) Why did they get increased glucose metabolism in the orbitofrontal cortex, but apparently NOT in the inferior temporal gyrus?  It seems that the radiofrequency was highest there, so if it was a direct effect on metabolism like they conclude with the orbitofrontal cortex, I wonder why they didn't see anything in the temporal gyrus.

2) What about HEAT?  One of the articles covering the paper stated that it couldn't be head because it occurred near the antenna rather than where the phone touched the head, but this isn't mentioned in the paper itself (or at least I didn't find it).  I would kind of like to see measurements of heat as well as radiofrequency, and see how they correlate (or not) with changes in activity.  Even if there's no effect, it's a good control to have.

Finally, keep in mind.  It's a 7% change in glucose metabolism.  That is TINY.  You get larger increases when you think about Disney Hipsters (really I just had to put that link in there because I love it!).  So I wonder if this increase really does have any meaningful effect.  It's an increase in glucose metabolism, yes.  But it's going to take WAY more information before we know what these changes mean, and even talking about cancer seems more than two steps ahead at this point.

EVERY bit of coverage ends with the note that Dr. Volkow uses a handsfree. Her thought is, why take any risk at all?  I agree with her, but not for brain metabolism, rather I worry about the probably much LARGER risk to your driving.  So get the handsfree anyway.

Nora D. Volkow, MD, Dardo Tomasi, PhD, Gene-Jack Wang, MD, Paul Vaska, PhD, Joanna S. Fowler, PhD, Frank Telang, MD, Dave Alexoff, BSE, Jean Logan, PhD, & Christopher Wong, MS (2011). Effects of Cell Phone Radiofrequency Signal
Exposure on Brain Glucose Metabolism JAMA, 305 (8) DOI: 2011;305(8):808-814

26 responses so far

  • gerty-z says:

    As a not-neuro, how do folks normalize these data to get a figure like 7% increase? It looks like the one on the left is more "hot" everywhere, not just where the arrow is pointing. Also, it seems like it wouldn't be hard to have "dummy" phones that you could heat slightly w/o emitting radiofrequency as a control, no? And why would the antenna be the source of the change? I'm skeptical...

    Anywho, thanks for another clear and even-handed deconstruction. 🙂

    • scicurious says:

      Ok, had to wait on this question until I had caffeine enough in my system (well, "enough" is relative. I'm no longer QUITE a zombie...). The figure of 7% comes from a comparison to the baseline brain metabolism in either a pre-scan or the baseline off condition. You take a template with specific voxel size and normalize the baseline data so it evens out, compare to the cell condition, and use voxel-wise t tests to compare specific brain regions (because the overall difference wasn't significant.

      Also remember the image you've got there is representativew, and of only one slice through the brain, so there might have been higher activity in the whole frontal lobe (which is what it looks like there to me), but that's just in that slice and just in that PERSON, so the whole thing may well have come out in the wash except for that little bit of right orbitofrontal.

      Well the antenna are where the RF is coming from, and according to their measures, it does appear to be coming from there. But yeah, I do wish they'd maybe done a heat control. It IS published as a "preliminary finding" so it's possible they are doing this.

  • Kees says:

    Could it be that the antenna of the cell phone is something like a miniature TMS device? Does TMS increase glucose metabolism much?

    In any case, I think it's highly unlikely that a cell phone is a serious health hazard. Perhaps the radio waves from a cell phone can directly influence your behavior slightly, but even if that's true, I don't think that it would be much cause for concern.

    • scicurious says:

      Good point! From what I can tell, the RF coming from the antenna would be a VERY different frequency than TMS. TMS appears to me a MUCH stronger stimulus (2 Hz, but the study here didn't list the cell phone frequency). But TMS does produce depolarization of cell potentials, and does increase glucose metabolism in cortical areas where it is applied (http://www.ncbi.nlm.nih.gov/pubmed/11170307), and the FDA has deemed it as reasonably safe...but ineffective for treatment of things like major depression which is what they were trying to get it on the market for.

    • Hi Kees -

      Very clever idea!

      - pD

  • fcs says:

    Nice post, and I love the Disney hipster memes. 🙂

    I kind of doubt a handsfree headset would help, because it's still pumping RF right into your ear. (If anything I'd think it was worse if it's the earbud type). A speaker-phone type system would work, though.

    • scicurious says:

      Yeah, see the kind of amusing thing is that people firmly believe that handsfree is totally safe, and studies have shown it has NO effects at all. So...yeah. Makes me think heat, maybe.

  • Andi says:

    From what I know, the glucose tracer for PET scans cannot be administered by drinking a fluid; the glucose will not pass through the blood-brain barrier.

    • scicurious says:

      Ah, thanks.

    • bsci says:

      Just to confirm, injections are used. As noted in the article, "Activation of the right cell phone was started 20 minutes prior to 18FDG injection and maintained for 30 minutes afterward to correspond with the 18FDG uptake period."

      • scicurious says:

        Yes, they were in this study. I was wondering whether other studies looking for different things might use drinkable tracers.

        • bsci says:

          I don't think ingestion is ever used for brain studies. A core part of the method is to have as good a handle as possible on when the radioactive tracer reaches the target region and the tracer concentration. Sending stuff through the digestive track adds way too much noise (and unnecessarily exposes the digestive organs to the highest levels of radiation). Even for radioactive glucose, with a half-life of 109.8 minutes, much of the radiation would be lost before it even reached the brain. Note that the entire recording here was done 30min after injection. Other common PET tracers have shorter half-lives.

          That all said, I know nothing about non-brain PET studies and could see ingestion being used if someone was studying something in the digestive tract.

          • scicurious says:

            To be honest, I was just remembering when Sci was younger and got appendicitis, they went to scan me and made me drink like a gallon of this orange stuff with a tracer. Didn't know what scan (this was before Sci was all sciencey), all I remember is the technician running the thing found my appendix on his coffee break, and came to tell me.

  • Sue W says:

    Nice post, thanks for this.

    @fcs Wireless earpieces use different frequencies (e.g. Bluetooth) and far less power than the kind of antiquated flip phone that I have. The transmitter of the normal phone RF is then located farther away from one's head. So if we assume some kind of RF effect, then handsfree should be "safer".

  • bsci says:

    I think both Sci & the NY Times posts are confused about the heating issue. Yes, the phone itself sometimes heats up, but that's not what concerns people. RF generating antennae create heat near them. The specific phone in this study has a maximum specific absorption rate (SAR) of 0.901 W/kg. For comparison, FDA and other countries have SAR limits for MRI machines. http://www.mr-tip.com/serv1.php?type=db1&dbs=Specific%20Absorption%20Rate
    The phone's SAR is lower than all of them meaning current knowledge says the body will be able to disperse the absorbed heat without problem.

    This is potentially relevant to the current study because the fact that the body can safely disperse heat doesn't mean it doesn't change anything. I could hypothesize that slight increases in cerebral blood flow (CBF) could be one mechanism for heat dispersion. As noted in their conclusions, CBF has sometimes been shown to increase with phone usage. It's possible this could cause region-specific glucose deposition with minimal if any changes in neural metabolism (If more radioactive blood flow to one region, tracer will be more likely to bind to cells in that region).

    I'm also curious if the cell phones might interact with the actual PET recording. I can't think of a clean mechanism, but I'd love to see recordings of an active and inactive cell phone next to a beaker of radioactive glucose.

    • scicurious says:

      You point about heat is actually what I was trying to get at. I don't think that the brain is running "hotter" or anything, I wonder if the increased glucose metabolism is a response. I'm not saying that the heat would be harmful because I don't think it would, I think this is a small change with probably very little effect. Thanks for the info on SAR, that helps clear it up a good deal.

  • becca says:

    If we're gonna snark on thinking handsfree = safe for brainz (even though the 'danger' to brains comes from the radiofrequency, which is just as bad with handsfree), shouldn't I be obliged to snark on you for thinking handsfree = safe for the driving (when the danger to drivers comes from the distraction of the conversation, which is just as bad with handsfree)?

    Also, a serious question. From the PET scan, it seems like there's a dollop of red on both sides with the cell phone on. Is it not significant on the side the phone was not on? To me, I can't see how this can be a direct effect. Which actually makes it more interesting...

    • bsci says:

      On a second skim, I'm a bit more underwhelmed by this paper... partially relating to Becca's serious question. What it comes down to is that there's extremely scant data in the manuscript. The image above is from a single subject so it's hard to draw real conclusions from it. Their real data is table 2, which shows that only the regions near the phone crossed a stringent statistical threshold. I have no clue if the bilateral dollops of red are an exception in this subject or are in most of the volunteers, but didn't quite cross the statistical threshold.

      The only other data in the paper is figure 3, which shows temporal plots of the cell phone effect in the areas that were already shown to have a phone effect. This is the classic circularity problem that social neuroscientists were criticized about:

      Considering how much press this is getting, this is one case where the paper could have benefitted from some supplemental data showing activity patterns in other regions.

    • scicurious says:

      I thought there was a paper somewhere saying handsfree made for safer driving...could be I'm out of date on that.

      I don't believe it was significant on the side the phone wasn't on...the image is a single subject, not a composite, the actual data is in a table, showing a 7% increase in activity only in the right orbitofrontal cortex. As bsci notes, a bit underwhelming, esp considering the press. But cell phones, brains, the kind of keywords that are going to light up the eyes of journalists.

      My real beef is if the signal is stronger in the inferior temporal lobe, is there no extra activity there? If so, why not?! Seems like if there was a major effect here that's where it would show up, right? I emailed Dr. Volkow with the question, and I'll let you know if she gets back to me.

  • Jerry Schwarz says:

    "In this case, they looked at glucose utilization over two days of studies. The participant would get two cell phones strapped on either ear and hung out in the PET machine for an hour. On one day (the order was randomized), both cell phones were off. On the other day, the RIGHT cell phone was ON, and receiving a message, but was on mute so the participant couldn’t hear anything (and so you wouldn’t see brain activity resulting from what the participant was hearing). The cell phone was the Samsung Knack Flip phone."

    There is something surprising about this protocol. Why did they only turn on the right cell phone? It seems that they ought to have randomized which ear had the active phone. Especially as they seem to be claiming that the effect happens on the side of the head with the active phone.

    And did they test whether the subjects knew which phone was active? This would have been a simple control to implement.

    And I'm always suspicious of "representative" figures. It is too easy to consider as representative the picture that best illustrates the point

  • Jon says:

    Wait a second. Would you dunk your computer in mineral oil without expecting some undesirable side effects? I mean I know it would probably work more or less (before it overheated), but something it's sufficiently complex that there are bound to be some issues.

    Let's face it; mental health or performance issues can arise over smaller things than a 7% metabolic rate increase, yeah?

    I don't think it is acceptable to dismiss a change like that in the way I am seeing done in the comments here. Honestly, this focus on cancer is a little bit backwards IMO, it's not the only potential problem we are looking at. In fact, I wonder if that misplaced focus is why it took so long for an experiment like this to be done, instead of endless epidemiological studies looking for cancer.

    It's known that a high power microwave pulses modulated with an audio vsignal can cause the individual being exposed to hear the modulating audio in their head. IIRC the effect was too fast to be attributed to heating and cooling, so assuming that the frequency of microwaves is too high to cause any sort of electrical activity at a frequency low enough to be detected by neurons seems to be false (at least at the frequency the experiment was done at, might not be 2.4 GHz though I guess).

    This whole thing also raises the question of whether a microwave oven would have a similar effect, as they tend to leak a lot more than 5 watts (which is about what a cell phone puts out).

    Fortunately there has already been some effort to design in reductions in the exposure to microwave radiation from cell phone antennas by placing the antenna a little farther away etc. i.e. the antenna is usually in the mouthpiece part of a flip phone these days, rather than next to the ear.

  • [...] ARE they doing to us? To our environments? Is it bad when you talk for a while and they get all warm and stuff? So I've begun digging through the lit. And just the other day, the brilliant and talented Desiree [...]

  • Nasreen says:

    Hey - great coverage of the overall issue. I'm really curious to get your commentary on a recent cell phones and health research conference held in Turkey: http://www.saferphonezone.com/?p=568

    Let me know if you want to take a look at the journals.


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