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.

1 comment:

  1. Idle thoughts department: I've had this idea of sequentially shaving very thin brain layers from a frozen brain and scanning each layer with lasers to produce a 3D map of the cells. I'd also want to determine the type of synapse maybe via a mix of laser colors. A blueray disk drive has a laser spot focussed to about half a micrometre which is about half the width of a nerve (I believe.)

    Then upload it to a computer, analyse the connections, maybe detect redundant parallel circuits to reduce the complexity by 98% or something, model the interfaces (hormones, senses, muscles, etc), convert to a program and run it on a massively parallel computer. Easy!

    Questions: Could it keep up with real time? I guess not. Would it think? What would it think? Is is cruel? (It would be a second life for someone who was dead so I'd think they might like the idea.) What would the ethics committee say?