♫ Oh, sugar sugar ♫

To say I had a sweet tooth as a child would be an understatement. I remember one Easter, I must have eaten over 40 Cadbury Creme Eggs in one sitting. My mom would put a chocolate centerpiece on the table, usually a bunny or an egg or something like that, and it would be surrounded with smaller treats, such as Creme Eggs. What ensued was a complex calculation of how many eggs I could eat before it would look like I ate them all. I had to factor in the fact that my brothers and sister would also eat some eggs, albeit at a slower rate. And I also had to squish all the little foil wrappers in the tiniest, most compact ball possible to make it look like I didn’t actually have that many. Those were the good days.

It’s no secret that children have a more pronounced preference for high-intensity sweetness. This preference may have evolved to make sure children seek out energy-rich nutrition during growth. Therefore, having a child with a sweet tooth was never really a cause for worry. Until now.

A recent study in the journal Addiction looks at the link between children with a sweet tooth and two other parameters: family history of alcoholism and depression. The researchers picked those two parameters because the pleasure derived from eating something sweet is generated by a reward system in your brain, and both alcoholism and depression affect this reward circuitry. The researchers looked at 300 healthy children, assessed their family history of alcoholism (via an interview with the mother), and tested them for depressive symptoms. They then tested the children for sweetness preference by having them taste sucrose solutions of different sucrose concentrations and asking them to choose which is their favorite. They also assessed the children’s liking for sweet treats in daily life.

The researchers found that almost half of the children were positive for family history of alcoholism, and one quarter of the children exhibited depressive symptoms, consistent with previous studies. When the researchers analyzed sweet preferences, it got messy. First, children with a family history of alcoholism preferred significantly higher sucrose concentrations compared with children with no such family history. Interesting, right? However, if from the total pool of children with a family history of alcoholism, you remove those who also show depressive symptoms, the alcoholism/sweet tooth link is no longer significant. Like I said, messy. Second, children who tested positive for depressive symptoms preferred significantly sweeter foods compared with children who didn’t exhibit depressive symptoms. Interesting, right? However, if you factor in the age of the children, this depression/sweet tooth link is no longer significant (this is because the intensity of the sweet tooth decreases with age). Guess what I’m about to say? That’s right, messy.

Overall, we can draw two conclusions. First, children with a family history of alcoholism AND exhibiting depressive symptoms prefer significantly sweeter solutions. Second, children exhibiting depressive symptoms MAY have a “sweeter tooth” compared with children who don’t exhibit depressive symptoms. Several theories, or a combination of these theories, could explain the associations observed in the study. First, if you read the fine print in the article, you’ll find that the mothers of children who have a family history of alcoholism and depressive symptoms are more likely to be obese. Perhaps these children are exposed to more sweets from an early age? Second, other studies have shown that adults with depression have a higher threshold for the detection of sweet taste. Therefore, it is possible that these children are less sensitive to sucrose and need a higher concentration of sugar to achieve the same level of sweet taste. Third, it is possible that the children with a family history of alcoholism and depressive symptoms have an altered brain reward system and require a higher concentration of sugar to activate the pleasure centers in the brain.

While this study suggests interesting associations, one thing is for sure, more experiments are needed to determine if having a sweet tooth means anything at all. Now excuse me while I unwrap the first Cadbury Creme Egg of the season.

Reference: Sweet preferences and analgesia during childhood: effects of family history of alcoholism and depression. (2010) Mennella JA, Yanina Pepino M, Lehmann-Castor SM, Yourshaw LM. Addiction. Feb 9 [Epub ahead of print].

Do you want to live? Yes or no?

In the early 2000’s, the Terry Schiavo case took the media by storm and pushed into the spotlight a number of ethical questions regarding patients in persistent vegetative state (awake but not aware). Evidently, none of this would have happened if we could just have asked her whether she wanted to continue living or not. A simple yes or no question. Could this be achieved? Can patients in a vegetative state communicate purposefully? A new study suggests they can.

The researchers looked at brain signals from 16 healthy patients and 54 patients with severe brain injuries who were in a vegetative state. The technique they used is called fMRI (for functional magnetic resonance imaging), a scan similar to one you would get for a joint injury, but instead of taking static images, fMRI measures blood flow in your brain. Presumably, if part of your brain is activated, there will be an increase in the blood flow in this area, and this will area will light up on the brain image.

The first experiment was done only with the healthy controls to establish that different cognitive tasks lead to the activation of different parts of your brain. While immobilized in the fMRI machine, the subjects were asked to imagine playing tennis. They then asked the healthy subjects to imagine walking through a familiar house. As expected, the brain scan images showed that each task activated a different brain region.

Armed with this control data, the researchers moved on to the patients in vegetative state. They asked each of the 54 patients to think about playing tennis and to think about navigating through a familiar house, and looked at the resulting brain signals. Of the 54, they found a grand total of five patients whose brain signals matched that of the healthy controls during a given task. This result suggests that some patients in a vegetative state can willfully influence their brain activity.

While this is an interesting finding in itself, there’s more. The researchers then took one of the five patients who showed the correct brain activity, and asked him yes or no questions. The patient was instructed to think about tennis when he wanted to answer yes, and think about the house when he wanted to say no. Out of the six yes or no questions he was asked (such as “Is your father’s name Alexander?”), he correctly answered five. Success!

The researchers and the media were quick to take these findings to the next level: with this new technique, we can now have brain damaged patients express their feelings! We can increase their quality of life! We can ask them important ethical questions! Well, hold on. While I do agree that this is a very interesting study, and that it will no doubt give a lot of hope to the families of patients in vegetative state, one has to be very careful with interpretation. First, let’s run the numbers: out of 54 patients, only five responded to the tasks. Out of those five, only one was tested. Out of the six questions asked, five were answered. While this represents a great achievement, we are very far from being able to extrapolate the potential of this technique. Second, the fMRI technique is expensive, imperfect, and very difficult to interpret. Third, certain words could possibly cue brain activity that may or may not be willful. I would like to see the researchers do an experiment where they just say the word “tennis” or “house” to healthy volunteers without asking them to imagine anything and see what kind of brain activity results. Finally, the fact that a patient has the cognitive ability to picture playing tennis does not mean he or she has the cognitive ability to make important, ethical decisions. So before we get all excited, I think we should keep things in perspective. But one thing is for sure: in this age of medical technology, we can set the Ouija board aside.

This is what fMRI data looks like

Reference: Willful modulation of brain activity in disorders of consciousness. (2010) Monti MM, Vanhaudenhuyse A, Coleman MR, Boly M, Pickard JD, Tshibanda L, Owen AM, Laureys S. New Engl J Med Feb. 3 [Epub ahead of print].

Eating Dolly

Remember Dolly? The first cloned mammal? The world’s most famous sheep? How would you feel about having Dolly for dinner, and I don’t mean to visit…

This week, I am writing about cloned meat in the food chain. We’ve come a long way in cloning techniques since Dolly (1996) and several farms in the United States are now producing cloned meat for human consumption. I thought I would review the literature and find an article on the safety of eating cloned meat. I’m not going to lie: I was biased going into this. I’m just not sure how I feel about a Dolly steak. As a scientist, however, I may not be biased in methodology, so I reviewed all the articles I could find on cloned meat as a source of food. Here is what I found:

• Cloned meat appears to be exactly the same as regular meat. Same nutrients, same properties, it’s virtually biologically indistinguishable.

• Animal models, when fed cloned meat for some time, seem perfectly fine.

• Animal models, when fed cloned meat and then made to reproduce, also seem perfectly fine, and reproduce just like animals fed regular meat, and the babies are fine, too.

Given the evidence, I have to tell you that there appears to be no hint of anything wrong with eating cloned meat.

So what? That’s it? We just drop it? The Food and Drug Administration was totally justified to approve cloned meat to enter the food chain in 2006? If you review the science, yes.

As someone who is ever careful about the quality of food, however, I personally have a few reservations. First, scientific reservations:

• Overall, I only found a handful of controlled studies.

• The longest-term study I have found looking at the effects of feeding cloned meat and milk to animals is 12 months. While 12 months is a very long time in the life of a rat (the species used in this particular study), that still may not be long enough. Especially considering we don’t actually have that much in common with the rat (except perhaps a love for food).

• The main study looking at how feeding cloned meat to animals impacts reproduction was done in rabbits. Is it me or do rabbits not normally eat much meat?

• While the data clearly suggests that cloned meat is just like regular meat, other scientific studies find that cloned animals have a higher fetal mortality rate and may be more susceptible to some diseases. Now there’s probably a reason for that, and until we find it, how can we be positive it’s not somehow affecting the meat?

That being said, proteins are proteins. And logically, cloned meat, as the evidence suggests, is likely identical to regular meat. The reason I would still chose not to eat it is more ethical than biological. With an ever-decreasing diversity on Earth, I can’t help but think that the mass production of cloned beings is a step in the wrong direction.

Because the laws on labeling cloned meat are still a bit fuzzy, what can you do if you would rather avoid cloned meat? One easy (albeit expensive) way to be sure is to go organic. In the last few years, both Canadian and American food authorities have declared that cloned meat or milk does not fit the organic bill. Another great way is to seek out meat from local producers, and get information on their practices. Why not visit the local farms? Road trip!

Sample of references: Effects of cloned-cattle meat diet on reproductive parameters in pregnant rabbits. (2010) Lee NJ, Yang BC, Hwang JS, Im GS, Ko YG, Park EW, Seong HH, Park SB, Kang JK, Hwang S. Food Chem Toxicol [Epub ahead of print].

Fourteen-week feeding test of meat and milk derived from cloned cattle in the rat. (2007) Yamaguchi M, Takahashi S. Theriogenology 67(1):153-65.

Cloning animals by somatic cell nuclear transfer-biological factors. (2003) Tian XC, Kubota C, Enright B, Yang X. Reprod Biol Endocrinol 1:98.

The eyes don't lie

Think back to the last time you used your car, or your bike, to get somewhere. When you reached your destination, what color was the car or the bike parked nearest to yours? Can you remember? Chances are, unless you opened your car door too fast and dinged the one next to you, you probably can’t remember. Now what if I was to tell you that while you can’t consciously recall this information, your brain might still know it? What if there was a way to get at this information? A recent study in the journal Neuron suggests there is a way: by reading your mind through your eyes.

The researchers made participants study three different scenes (for example, a park, a lake, a kitchen) each superimposed with a different face. After a short break, the participants had to do a test. They would be presented with one of the three scenes from the study phase, and after a delay, all three faces seen in the study phase were superimposed on the test scene. All the participants had to do was identify which of the three faces was the one that initially corresponded with the test scene. During the test, two parameters were evaluated: the first one was whether the participant correctly identified which face corresponded with the test scene, and the second parameter was where the participant was looking on the screen, and how much time he or she spent looking at each of the three faces. This was done through a technique called eye-tracking, where a camera records the position of your eye-gaze.

Here is an example of the task

What the researchers found is that the participant’s eyes spent significantly more time viewing the correct matching face (the “right answer”), even when the participant selected an incorrect face as the answer. So what this means is that even when the participants couldn’t consciously remember which of the three faces was the right one, their eyes lingered the longest on the correct face.

In addition to the eye-tracking study, the researchers were looking at brain signals from the participants and determined that the hippocampus, a brain region we already knew was involved in conscious memory retrieval, was also supporting memory even when the participants were making incorrect responses. In a way, this means that your hippocampus supports the expression of memories through your eye-movements, even when you’re not consciously remembering correctly.

The relevance of this study lies in the fact that in some circumstances, the movements of your eyes is a more truthful and reliable account of memories than your verbal accounts. I’m sure you can imagine instances when this could be helpful: for example, to study the memory processes of non-verbal beings, such as babies or chimpanzees (who doesn’t want to know what a chimpanzee is thinking?). However, eye-tracking could also be used to get information from someone who is attempting to withhold it (surely, a more acceptable alternative to waterboarding). So next time you have something to hide, invest in a good pair of sunglasses…

This guy wants to know what you're thinking.

Reference: The eyes have it: hippocampal activity predicts expression of memory in eye movements. (2009) Hannula DE, Ranganath C. Neuron 63:592-599.

Saving the humble pie for another day

The results are in: Scientific Chick won the 2009 Canadian Blog Award for best blog in the Science and Technology category!

Since this was rather unexpected, I did not prepare a speech. But I do want to say big thanks to everyone who voted! I really enjoy writing this blog, and it means a lot to me that there are people out there who enjoy reading it.

Thank you!

Cell phones: curing brain diseases since 2010

If you are like most people, and in particular like everyone I take transit with on a daily basis, you probably spend a fair amount of time talking on your cell phone. If that’s the case, you’ll probably be happy to learn that in 2007, the World Health Organization declared that cell phones are A-ok. Nothing to worry about health wise. Not at all like sticking your head in a microwave. But you’ll be even happier to learn that in 2010 (fresh off the press!), a study published in the Journal of Alzheimer’s Disease suggests that not only is using your cell phone harmless, it might actually be good for you.

The researchers looked at the effect of exposing mice to high frequency electromagnetic fields (similar to the ones you are exposed to when chatting on your cell phone) for a long period of time (2 hours a day for 8 months). They used both normal mice and a mouse model of Alzheimer’s disease. An Alzheimer’s mouse is a transgenic mouse that has a gene that causes some of the manifestations of Alzheimer’s disease in humans.

At the start of the study, before the exposure to the electromagnetic fields, the researchers tested the mice on memory tasks, and as expected, the Alzheimer’s mice were clearly impaired compared with the normal mice. After two months of exposure, no change was observed in either type of mouse. However, after 8 months of exposure to the cell phone-like electromagnetic fields, the Alzheimer’s mice did significantly better on memory tests compared with Alzheimer’s mice who didn’t receive the treatment. Normal, non-Alzheimer’s mice also showed cognitive benefits due to the electromagnetic fields compared with normal mice that didn’t get the treatment.

Time to get Grandma a cell phone? Not so fast.

You may have seen this story in the news. It may have sounded like we finally found a cure for Alzheimer’s disease, and, as a bonus, it’s non-invasive and has no side effects. You may have started thinking of a business plan that involves sewing cell phones into pillowcases for the elderly. Trust me, I thought of this. However, as per usual in the world of science, it’s probably not that simple.

First, I can tell you this: mice skulls are thin, weak, and very easy to cut through with just a regular pair of tiny scissors (how sad is it that I know this from experience?). The skull of a mouse is very different from that of a human, and this means that while the electromagnetic field might penetrate well into mice brains, this may not happen in humans.

Second, the mouse model of Alzheimer’s disease, while widely used and our best tool for these types of studies, is flawed. So extrapolating the results to human Alzheimer’s disease is definitely premature.

Third, if you read the article carefully (I did it for you, so no worries), you’ll find that exposing the older mice to electromagnetic fields has one interesting side effect: an increase in body temperature. It then becomes difficult to tell if the memory enhancement observed is due to the temperature change or the electromagnetic fields. However, this is not necessarily a bad thing. I, for one, would much prefer to prevent cognitive decline by a daily regimen of quiet hot baths then by talking on the phone (though when I was a teenager, my mom would have guessed otherwise).

Finally, there was another sneaky side effect to the exposure, one that was seen only in younger mice: a decrease in three brain compounds involved in battling oxidative stress, including a very important antioxidant. The authors go over this finding somewhat quickly, and suggest that this can be interpreted as a good thing. Unfortunately, I happen to have studied this particular antioxidant quite a bit and I am of the opinion that the finding can also be interpreted as a very bad thing.

Overall, I don’t want to sound like a complete downer. This study was well conducted, showcases very interesting findings, and certainly gives us hope that maybe something can be done for Alzheimer’s disease. But I won’t be sowing a cell phone in my pillow just yet.


Reference: Electromagnetic field treatment protects against and reverses cognitive impairment in Alzheimer’s disease mice. (2010) Arendash GW, Sanchez-Ramos J, Mori T, Mamcarz M, Lin Z, Runfeldt M, Wang L, Zhang G, Sava V, Tan J, Cao C. Journal of Alzheimer’s Disease 19:191-210.

Black and white television

The United States recently elected their first black president. In this era of multiculturalism, can we consider ourselves a race-blind society? If you were to ask around, chances are most people would claim they do not behave in a racist fashion. Unfortunately, racial biases are still around us, and a recent study in Science makes a worrying discovery about the subtlety of racial biases in every day television programming.

The study looked at 11 popular television shows that include recurring white and black characters of roughly equal status (for example, characters could include a black detective and a white detective or a white doctor and a black doctor, and overall, black and white characters are equivalently distributed in the hierarchy). The researchers selected sample clips from the 11 shows and removed the audio track. They then asked a number of white young adults to watch the soundless clips and rate how well each character seemed to be treated by other characters and how much it seemed each character was liked.

You’d think if the character statuses are roughly equal, they would elicit similar non-verbal responses. Well, think again. Overall, white characters elicited significantly more favorable responses when compared with black characters, meaning the subjects rating the clips thought that the white characters seemed more liked and better treated by others than black characters. The interpretation of this study is that common television programming exposes us to race biases. The subtlety of this bias lies in the fact that it is non-verbal: when a new group of white young adults was asked to read the written transcript of the clips, no such biases were found. The researchers then took the study further and showed that the perception of the non-verbal biases in television shows can influence one’s race association and racial attitudes.

What is the reason for the presence of this race bias in television shows? Are the actors spontaneously generating them? Are they scripted? What other types of biases might be communicated through television? This study definitely gives us food for thought…

Reference: The subtle transmission of race bias via televised nonverbal behavior (2009) Weisbuch M., Pauker K., Ambady N. Science 326:1711-4