We are about half way through the Society for Neuroscience 2006 in Atlanta, and it’s time for some general impressions and notes for future reports. Some of the lectures and symposia have been interesting and revealing, others have required too much previous knowledge for me to fully appreciate.
But let’s start with today’s lectue by Judy Illes, who gave an interesting talk on the different aspects of neuroethics. Much of the talk was dedicated to the aspects of incidental findings (IF). It gave rise to quite a few thoughts to me. First of all, the problem with IF seems to focus a lot on the ethics on behalf of the subject. Should we tell in case we find something, should we ask people in advance if they want to know, how can we secure our research to avoid as many IFs as possible? It struck me that as a researcher, there is an additional motavion: external validity. If you are studying healthy volunteers you want them to BE healthy volunteers. Any IF will thus influence your data in an unwanted way. To me this is not trivial. It is part and parcel of your scientific motif. So for this reason alone we should make as sure as we can that we are indeed analyzing healthy subjects. The better screening we can do, the more sure we can be that we’re studying what we aim to, e.g. healthy ageing.
Another issue that Illes put forth was the prophylactic scanning of older people. Just like women today can get a mammography to detect breast cancer as early as possible, should we also offer brain scans to people above 65 in order to detect degenerative disease as early as possible? In order to answer such a question, we should know more about the relative costs of 1) prophylactic scanning, as well as the feasbility of such offering in a hospital setting (e.g. manpower), and 2) the cost of degenerative disease in society as a whole. Ideally, we should be able to offer brain scanning of all people to detect diseases. In reality, this is not feasible either in terms of logistics or economy. But if it turns out that Alzheimer’s costs a certain proportion more than the screening effort (and early interventions if AD is detected) then there should be little reason not to do this. This, of course, given that our current methods to study individuals are good enough. I’ll put this as a separate point next:
If we are to detect brain disease as early as possible, our current methods should still be significantly improved. Yes, we can indeed visually detect degenerative disease at an early stage, but in order to study the very earliest signs of pathology we must do proper statistical methods, and normally in a group by group study. To have the knowledge about any given person’s volume of, say, the hippocampus, we must know more than just the mean size of the hippocampus. Just as one does in neuropsychology, one should know about the normal distribution, and given for different groups. For neuropsychological tests you would divide norms and distribution scores into gender, age, education and maybe other factors. In neuroimaging some of the same factors might apply, but other factors such as genotype, nutrition, and of course body weight should be used as separate factors. At this stage this is not done. In this sense, I cannot possibly know what a person’s hippocampus size means at all.
It’s not much better with functional imaging — it is possibly worse. It is possibly very nicely illustrated by the recently published study by Owen et al. that I blogged about previously. Owen et al. found that for given tasks such as imagining playing tennis, there was really little difference between healthy, conscious individuals and a patient in vegetative state. The result was interpreted as signs that the unconscious patient was really conscious. As I have noted, this is really an unwarranted conclusion. Although the images are really visually impressive, they tell little about what is normal, and normal variance. So where do the patient’s images fall in compared to the normals? There are differences, although tiny, but are they within or outside normal variance? This topic is far too complex to resolve by merely comparing BOLD fMRI scores, and it surely cannot be used to say anything about one person’s brain relative to a “mean brain” value.
In terms of incidental findings, my own practice is to do a thorough screening of medical history and neurological + psychiatric signs both in the person and his/her family. If you’re doing functional imaging, blood preassure, even if well treated, should also be a concern. Neuropsychological testing is a must, as is the involvement of professionals who know how to look at brains, such as radiologists or neurologists. If you are doing studies of healthy individuals, make sure they are healthy.
And hey, as a teaser, tomorrow I’m doing an interview with Judy Illes. If all goes right, I hope to provide the audio of that very soon. In the meantime, I’ll attend the Neuroethics Social tonight and get back to you.