Posted on March 21, 2012 at 8:10 AM
A recent post at Neuroskeptic discusses whether neuroimaging studies may provide a misleading picture of the brain. The issue is made relevant due to recent studies that demonstrate that for simple tasks, the brains were more or less globally active:
Both studies found that pretty much the whole brain “lit up” when people are doing simple tasks. In one case it was seeing videos of people’s faces, in the other it was deciding whether stimuli on the screen were letters or numbers.
The big surprise – should we take their word for granted – is that the whole brain is active whenever people do these simple tasks, and that it most likely only can be found when looking at a lot of people (most studies use around 20 people in fMRI studies).
There are several problems with this “big problem”, and just to name a few:
- Task unrelated images and thoughts (TUITs) and Mind wandering: since the 60s and 70s, psychology has studied what happens whenever people are relaxing, or doing very repetitive tasks. These studies uncovered that these states were highly active, not “passive” in any sense. This fact seems to have been forgotten in so many studies on the brain’s “default mode” and “resting state”, which surprisingly has uncovered increased activation in a number of widespread brain regions for “less” active tasks. Thus, having your subjects doing a highly repetitive – and even very boring – task is related to mind wandering. That such an active state would produce large-scale activation throughout the brain should come as no surprise.
- The conscious brain: being conscious about something seems to be related to large-scale “global” activation in the brain, including the parietal, prefrontal, temporal cortices along with structures such as the thalamus. Should we be surprised that such regions are largely activated when 1.000+ subjects are scanned while conscious?
- Individual differences: yes, even large individual differences between subjects may – when you are testing 1.000+ people – provide the false impression of a general large-scale activation of the brain “in all people”
So I don’t buy it: I think we can trust the fMRI data we have thus far. There are many challenges in using these measures, and many studies fall prey to a lot of the validity, reliability and sanity checks one can (and should) apply. But the purported problem by Neuroskeptic is, IMO, misfiring.