Anicca-vijja

This is the ‘first’ blog and I knew at once what it should be about: The new findings that heavily criticize the general findings of neuroimaging studies. A summary in German can be found in one of the lastes issues of ‘Gehirn und Geist’ (04-09, p.69) by Prof. Fritz Strack. Let’s look what is problematic besides the fact that neuroimaging studies do permanently perform a false logical conclusion, because they attribute characteristics of ‘whole’ human beings solely to their brains and neglect the rest of the body (and the mind)??

Telepolis published a short summary of the research of Edward Vul, a PhD student at the MIT in cambridge (USA) on ‘voodoo correlations’ and ‘non-independence error.’  In a first article he and colleagues write about artifical exaggerated correlations between voxels and external variables. These correlations are sometimes higher than the reliabilities which is far from being realistic! This was found not only in one, but in many studies that were re-analyzed … and not to mention all those articles that were published in high rated journals (but not re-analyzed). Additionally, in another article Edward Vul and colleagues concentrate on the selection of the analyzed brain areas (voxels). These were not independent from the behavior measurements that were done at the very same time. This means that from thousands of voxels those were selected for further analyses that showed a maximum correlation with the external behaviour measurements. Of course all further statistical relationships were high – but are they real or a methodological artefact? – that’s another story to be told.

Another article from Sirotin & Das (Nature 457) questions one of the most basic assumptions of neuroimaging studies: the covariation of local brain activity and blood flow. In an experimental study with animals the authors compared the neuronal firing of cells (direct measurement of cell firing) with the intensity of the blood flow. The results showed that both parameters did not correlate continuously with each other.

So what now? At first we should congratulate the cited researchers for their courage and the journals also for their courage to publish these important findings. What is needed in neurobiology and neuroimaging studies is a methodological discussion. Results should not or even must not be discussed without giving importance to methodological questions. Other disciplines like psychology or sociology have regular discussions of this kind (although sometimes the discipline does not considers change, e.g. ask a German psychologist why nobody does  Bayesian statistics?). I don’t like the last sentence of so many articles like ‘further research is needed,’ but this time I think – yes – these findings have to be understood properly and the experiments that led to their results have to be repeated.

References:

Sirotin, B. Y. & Das, A. (2009). Anticipatory Haemodynamic Signals in Sensory Cortex not Predicted by Local Neuronal Activity. Nature 457, 475–479.

Vul, E., Harris, C., Winkielman, P. & Pashler, H. (in press/ 2009). Voodoo correlations in social neuroscience. Perspectives on Psychological Science.

Vul, E. & Kanwisher, N. (in press/ 2009). Begging the question: The non-independence error in fMRI data analysis. To appear in Hanson, S. & Bunzl, M. (Eds.). Foundations and Philosophy for Neuroimaging.