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...

It has been recognised for millennia that risk of mental illness (broadly defined) tends to run in families. Modern science has confirmed that psychiatric disorders of all kinds are highly heritable – that is, the majority of the variation we see across the population in who is at risk of developing these conditions is genetic in origin. However, these conditions are not inherited in a simple “Mendelian” fashion, with clearly segregating risk, like cystic fibrosis or sickle-cell anemia. Instead, their inheritance is “complex”, which means that many genetic variants are at play, along with non-genetic factors. In addition, despite clear familial risks in general, many individual cases are “sporadic”, with no affected relatives. The last decade has seen tremendous efforts by many hundreds of scientists across the globe aimed at identifying the genetic risk factors and better understanding the etiology of psychiatric conditions.   The hope is that elucidating the genetics of these...