Month: January 2008

This case report from a 2001 study describes a patient with persistent headaches who experienced ‘phantom teeth’ – the sensation of non-existent vampire-like teeth in her mouth.

‘Phantoms‘ are often the result of having a limb or other appendage removed and can affect almost any part of the body (indeed, phantom penises have been reported in the medical literature).

In this case phantom teeth seem to have occurred after surgical removal of the gums, although this case is particularly interesting because the phantoms are for teeth that were never there in the first place.

Phantoms are thought to arise when the brain’s map of the sensory areas becomes distorted during re-organisation, after the actual sensations from the removed appendage stop.

A 52-year-old woman was referred to a neurologist because of right facial pain radiating from the malar region diagonally to the right upper lip area. She had pain for several months following upper and lower surgical resection of hypertrophic gums. The pain was severe, constant, and interfered with her sleep. She had no gustatory sweating or flushing of her face or neck. She developed symptoms of depression because of the chronic pain…

She reported a constant sensation of having two long extra upper canine teeth growing in front of her normal canines that felt like they were pressing on her tongue. The sensation was experienced as someone with vampire-like long upper canines (“Dracula’s teeth”)…

There was no family history of gum hyperplasia or supernumerary teeth. She complained of poor taste, forgetfulness, sleep fragmentation, and high-pitched ringing noises in her ears of long-standing. She had no burning of her tongue.

Link to abstract of scientific study.

Today’s edition of Nature has some commentary from scientists responding to their recent feature on ‘optimising’ the healthy brain with pharmaceutical drugs.

I suspect the letters have been edited a little though, as the first, from developmental psychologist James M. Swanson and neurobiologist Nora Volkow (who is also director of the National Institute on Drug Abuse) seems to suggest that enhancement drugs risk being addictive because:

…cognitive enhancers such as the stimulants methylphenidate (Ritalin) and amphetamine amplify the activity of dopamine, a neurotransmitter that increases saliency, making cognitive tasks and everyday activities seem more interesting and rewarding. This learned experience can lead to abuse of the drug and to compulsive use and addiction in vulnerable people.

These drugs are widely used for cognitive enhancement, but the issue is hardly new as these are relatively old drugs that almost solely target the dopamine system, whereas the newer ‘cognitive enhancement’ drugs (most notably modafinil) work in a quite different way (modafinil alters dopamine, among other effects, but it’s hardly comparable).

Hence, they do not have the same pharmacological potential for abuse and simply aren’t found to be as addictive as the amphetamines in the ‘real world’.

In fact, when the Nature article asked the hypothetical question whether you would take an enhancing drug if it had no side effects, it was almost certainly inspired by modafinil.

While the drug isn’t side-effect free (several are common) it tends to be significantly less risky than your typical high-charge dopamine agonist such as amphetamine, which can cause cardiovascular problems and psychosis to name but a few of its dangerous effects.

That issue aside, one of the most interesting points is made in a letter from philosopher Nick Bostrom who argues that drug companies should be allowed to develop enhancement drugs without having to specify an illness to treat.

He argues this is because the current system demands that drugs are licensed for a specific disorder, which means new disorders get invented (‘disease mongering‘) as a way of legitimising the sale of drugs which are helpful but for less serious problems of living, such as low-level anxiety, persistent tiredness or normal memory decline, but are not significant medical treatments.

So maybe the solution to the drug companies warping medicine is to allow them to sell drugs as ‘tonics’, rather than medications. Certainly food for thought.

There’s several other responses on the ethics and experiences of cognitive enhancement from some of the leaders in the field, so well worth a look through.

Link to ‘brain doping’ correspondence in Nature

It’s not often a children’s book on hallucinogenic drugs gets written, but this seems to be one of those occasions. Matt Hutson has scanned in some remarkable pages from exactly such a book, published in 1991.

Apparently it’s quite comprehensive, covering everything from neurons to shamans, and is also full of funky illustrations.

The prose is lucid, but the pictures crack me up. Take the cover. Look kids, in a drug free zone, you can do all kinds of things, like play tic-tac-toe. Or even watch people play tic-tac-toe! And remember, friends don’t let friends wear non-footie pants.

In some cases the book might be counterproductive: “Have you ever looked at yourself in an amusement park mirror? Look what happened to you! Now, try to imagine that the whole world looked that way to you.” Awesome! Where can I get some?

Link to Silver Jacket on ‘Focus on Hallucinogens’.

Memoirs of a Postgrad has got a great write-up of a new low-power MRI machine, the technology that does most of the structural and functional brain scans. Even the smaller MRI machines need huge electromagnets, but this new technology uses magnets thirty thousand times weaker to image the brain.

In a standard MRI machine, a strong magnetic field is used to align the proton in each of the hydrogen atoms before using an RF pulse to knock them out of alignment. As they snap back into alignment with the magnetic field, they emit a signal which can be detected and used to create a 3D image. In the new version, the very small magnetic field isn’t enough to align the protons, so a short duration (1 second) magnetic pulse of slightly higher magnitude (30 millitesla).

The resulting signals are very small, so an array of highly sensitive magnetometers are used (so-called superconducting quantum interference devices, or SQUIDS). A hugely important additional advantage of using these SQUIDS is that they are also used in the MEG (magnetoencephalography) imaging technique. This potential for MRI and MEG using the same machine raises the intriguing possibility of producing simultaneous structural images (using the MRI) and brain activation maps (using the MEG).

Unfortunately, the use of SQUIDs dashes any hopes of making the machines much smaller.

The SQUID sensors need to be extremely cold (working at approximately -170 degrees C) and so are usually bathed in liquid nitrogen, meaning a huge insulated tank sits atop the scan area.

IEEE Spectrum magazine has an article with some images from the new type of scanner, which look pretty fuzzy at the moment, but apparently can better distinguish tumours in the brain and will undoubtedly become clearer as new software is developed.

Link to Memoirs of a Postgrad post.
Link to IEEE Spectrum article.

Bad Science has a fantastic article on antidepressants and the widely-promoted but scientifically unsupported ‘low serotonin theory’ of depression.

Owing to a huge advertising push by drug companies, not only the ‘man on the street’, but also a surprisingly large numbers of mental health professionals (clinical psychologists, I’m look at you) believe that depression is linked to ‘low serotonin’ in the brain.

The only drawback to this neat sounding theory is that it is almost completely unsupported by empirical evidence or scientific studies.

Experiments that have deliberately lowered serotonin levels in the brain have found that it is possible to induce ‘negative mood states’ (usually milder and as short-lasting as a slight hangover), but these do not even begin to compare to the depths of clinical depression.

In terms of patients with the clinical mood disorder itself, not a single study has found a link to reduced serotonin.

Bad Science neatly reviews the science, and also discusses a new research study which chased up journalists that propagated the myth to ask for their sources.

Needless to say, none of them had any sound scientific basis for their claims.

This is not to say that antidepressants don’t help treat depression, (evidence suggests they do – although the effect is more modest than drug companies would have us believe), or that neurobiology isn’t important (by definition, if it’s a change in thought and mood, it’s a change in brain function).

If you’re interested in the history of how the ‘low serotonin hypothesis’ came to be thought up and then subsequently promoted, despite the lack of evidence, Professional Psychology: Research and Practice recently published a great article on the topic [pdf].

Link to Bad Science on the serotonin myth.
pdf of article on the history and popularity of the myth.
Link to excellent PLoS Medicine article on evidence and adverts.