Wiring the Brain

Clever, elegant and extremely powerful – techniques to activate specific sets of neurons with light have the potential to revolutionise cellular and systems neuroscience.   Optogenetics has already been used to address a number of questions which have been resistant to answer by other techniques, and also holds great promise for neurotherapeutics and prosthetics.   A new paper adds another approach to the toolkit – the ability to activate neurons with a radio frequency magnetic field.   While very much a proof of principle, with a ways to go before it proves its worth, this approach offers some obvious advantages over optogenetics, most obviously that magnetic fields pass into brains much more readily than light.   When trying to figure out what different brain circuits do, one of the most obvious experimental approaches is to ask: what happens if I make these neurons fire? Neuroscientists have traditionally used electrodes to activate neurons in the brain or in slices of brain tiss

In a recent post , I presented the evidence that sexual preference is strongly influenced by genetic variation.   Here, I discuss the neurobiological evidence that shows that the brains of homosexual men and women are wired differently from those of their heterosexual counterparts.    First, we must consider the differences between the brains of heterosexual males and females.   These differences are extensive and arise mainly due to the influence of testosterone during a critical period of early development (see Wired for Sex ).   They include, not surprisingly, differences in the number of neurons in specific regions of the brain involved in reproductive or sexual behaviours as well as differences in the number of nerve fibres connecting these areas.   But they also involve areas not dedicated to these types of behaviours, such as the cerebellum , for example, which is involved in motor control among other things, and which shows a very large difference between men and women.   A