Wednesday, April 30, 2008

Critical: construction of the cortical connectome

The Human Connectome - A Structural Description of the Human Brain (Sporns et al)

One of the major limitations in the effort to improve our understanding of the brain-mind relationship is the lack of available data on the arrangement and connections of and among neurons in the brain. The authors of this article propose "connectome" as the name for this important data set, and suggest that the data set include details on neuron position (using a common coordinate system), the absence or presence of connection(s) to other neuron(s), and, if those connections are present, information on the type of connection (ie. excitatory or inhibitory) and the biochemical / biophysical details of the connection. Furthermore, the authors suggest a strategic approach to the development of the connectome: given that one of the primary uses of the connectome will be to establish the link between brain activity and cognitive activity, it would make sense to establish the connectome of the cortex first. The authors further suggest that the connectome should first be described at a larger scale than individual neurons, given the enormous number of neurons in the human brain (approximately 10^11), the even larger number of connections among neurons (approximately 10^13), the plasticity of individual neurons and synapses, and the apparent role of groups of neurons (fibers) in brain function. Although it is difficult to isolate functional groups of fibers, the authors propose that a particular MRI method known as diffusion tensor imaging (DTI) could be useful in developing this initial draft of the connectome.

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