Wednesday, July 29, 2009
Mapping the human brain "connectome"
It seems that almost everything can come now with an "-ome" suffix (referring to a totality of some sort. Beyond the original "genome" we now have a long list, including the proteome, speechome, mechanome, etc.). A massive project to establish a human brain connectome, or map of all brain connections, has just received a 30 million dollar cash infusion from the N.I.H. This is an unbelievably daunting task, Over the past century, neuroscientists have used three main sets of anatomical approaches to study neural connectivity: single-cell impregnation, optically based tract-tracing and electron microscopy. More recent techniques involve attaching color markers to intrinsic neuronal labels (shown in figure). Resolution at the electron microscope level, so far done only for the small nervous system of the nematode roundworm, is still technically inaccessible, so that the work will actually be on lower resolution of nerve tracts. But... I wonder then about the minor detail that no two human brains are the same. Even the brains of identical twins have been shown to differ significantly in their activation patterns and connectivity. (The same variability also confounds comparative genome studies.) While it will indeed be exciting, as it was for the human genome, to be told "We now have the first human brain connectome," an awesome amount of work then must follow.