The Connectome

What is a Connectome?
Genomics is the attempt to map the entire genome of a given organism. A similarly ambitious goal is connectomics — mapping all the connections in a neural system, particularly that of retina and brain. Making such maps is key to understanding our senses, thoughts, motions, emotions, decision making processes, and their disorders. This is a grand challenge in science, but precise nanoscale tools have not been able to cope with the labyrinth of normal brain connections, much less explore neurologic disorders of any system … until now.

How is a connectome map built?
Electron microscopy has been the most powerful way to build tiny brain map snippets … like Gallileo trying to map Mars with a hand telescope. A cube of brain smaller than a pencil point contains over 10,000 nerve cells, over ten million connections, and more possible connection patterns than stars in the known universe. With conventional tools, mapping this tiny piece of brain would take centuries to millenia. The Retinal Connectomics Laboratory, in collaboration with teams at other institutions are building retinal connectomes to understand how these complex sensory networks are constructed and function, and how they break in disease. The tools and much of the data used to build these connectomes are freely available to all.

A Connectome Flythrough

Creating such connectome maps requires high-speed automated imaging and automated computational map-building and massive storage. A single 3D connectome map can require more storage space than 100 desktop computers. In the Marclab, James Anderson has built specialized connectome viewing software to see into such large images and trace their connections.

Why build connectome maps?
Simply to understand diseases that change brain wiring. Such disorders have annual US health care and lost productivity costs of $100 billion and inestimable personal cost.

  • Traumatic brain injury is a major public health problem with over 500,000 new cases occuring annually, many progressing to long-term disability.
  • Alzheimer’s Disease (AD). By 2010, over 5 million Americans are projected to have AD. Disappointing drug trials have been reinforced by new data showing that AD triggers large-scale brain rewiring.
  • Epilepsy affecting 2.5 million Americans has proven to be a major challenge due to our lack of understanding of the scope of altered brain wiring.
  • And of the Americans with advanced macular eye disease (1.7 million), diabetic retinopathy (4 million) and other rewiring retinal degenerations, over 2.4 million are blind or severely impaired.

If we can uncover the exact nature of these and other rewiring anomalies, we may be able to understand how to ameliorate them for the first time in the history of medicine.