Wiring the Brain

Figuring out the neural basis of differences between individuals or groups in all kinds of psychological traits or psychiatric conditions is a major goal of modern neuroscience. In humans, investigating this has necessarily relied on non-invasive tools like functional or structural magnetic resonance imaging (MRI). Many thousands of studies have been published following a similar design: measure some functional or structural neuroimaging parameters across the whole brain and compare them across individuals or groups to look for ones that are statistically associated with variation in some psychological trait, performance on a cognitive task, or membership of one or other group. Most of these studies have sample sizes in the tens or at best the low hundreds. A new study by Scott Marek and colleagues shows convincingly that those sample sizes are at least one or two orders of magnitude too low to produce reliable results.   This shouldn’t really be news to anyone who’s been payi...

We scoff at the folly of phrenology – the simplistic idea that the size and shape of bumps on the skull could tell you something about a person’s character and psychological attributes. It was all the rage in the Victorian era (the early to mid-1800s) in the UK and the US especially, with practitioners armed with calipers claiming to measure all kinds of personal propensities, from Acquisitiveness and Combativeness to Benevolence and Wonder. The skull bumps were just a proxy, of course – the idea was that they reflected the size and shape of the underlying brain regions, which were what was really associated with various traits. It all seems a bit quaint and simplistic now (apart from the entrenched association with racism ), but while we may like to think we have moved on, a lot of modern human neuroscience is founded on the same premises.    - The first premise is that different mental functions or psychological traits can be localised to specific regions of the brain. ...

A few days ago there was a minor Twitterstorm over a particular paper that claimed to have found an imaging biomarker that was predictive of some aspect of outcome in adults with autism. The details actually don’t matter that much and I don’t intend to pick on that study in particular, or even link to it, as it’s no worse than many that get published. What it prompted, though, was more interesting – a debate on research practices in the field of cognitive neuroscience and neuroimaging, particularly relating to the size of studies required to address some research questions and the scale of research operation they might entail. What kicked off the debate was a question of how likely the result they found was to be “real”; i.e., to represent a robust finding that would replicate across future studies and generalise to other samples of autistic patients. I made a fairly uncompromising prediction that it would not replicate, which was based on the fact that the...