Here are my notes from the TED talk of Dr. Sebastian Seung from MIT. I recommend viewing the presentation--although about 17 minutes long it is entertaining as well as showing some great graphics of the imaging and technology
- Your genome--your entire sequence of your DNA
- Small differences in genome make us who we are
- Are we more than our genes? I would like to think so.
- Well what am I then? I am my connectome
- C elegant was the worm that had the first mapping of all neuron connections
- But human brain has 100 billion neurons--many connections between these neurons
- Maybe our personal memories are coded in the connections
- I propose this hypothesis: I am my connectome--my pattern of connections between neurons
- How do we find connectomes in the human brain?
- Technology provides some advances in understanding these connections
- Thin slices of mouse brain can be imaged in three dimensions
- A three dimensional model allows for imaging synapses--connections between neurons
- Neurotransmitters provide the chemical message connections
- How do we move from one synapse to looking for connectomes?
- One key challenge--who do the brains of men and women differ?
- Our brains are like spaghetti--each piece touches many other pieces
- The complexity of these connections make some feel the task is impossible
- It is easy to despair at the difficulty of the task
- Some day a fleet of microscopes will be able to see all the neuron connections
- Some day supercomputers will use these images to see an entire connection
- I am working on a small piece of this challenge
- Our connectomes change over time as we age and develop
- Synapses are created and eliminated
- Neurons are created and eliminated
- What causes these changes?
- Some is programmed by your genome but other changes are due to environmental experiences
- Even genetically identical twins have difference experiences and therefore different connectomes
- Here is a metaphor for the connectome: Neural activity is the water of a stream--the connections determine the pathway of this stream
- A connectome is like the bed of a stream guiding the water of the stream
- However, over time the stream of water changes the river bed
- Neural activity is the basis of thoughts, feeling and perception
- Neural activity is the stream and the connectome is the river bed
- Memories may be chains of connections in neurons
- The sequence may guide specific memories, i.e. memory of a piano sonata
- Total length of wires in the brain--I estimate millions of miles, all packed in your brain
- In truth, we can't see the brain in enough detail to see wiring abnormalities in disease such as autism and anorexia
- Our research has philosophical implications
- Death is the loss of your individual neuronal connections: your connectome
- I propose we attempt to find a connectome in a person who has died (and had brain frozen) to see if it may be still intact and provide re-creation of an individual
- This voyage of self-discovery is not just for scientists but for all of us.
In a 2009 Neuron paper (direct link) is a more technical summary of some of the research advances in this topic. He notes that key technique advances have included:
- fluorescent protein labeling to mark active synapses
- coupling electron microscopy with serial sectioning techniques
- automated cutting and processing of brain slices
- computer-assisted methods to speed up image analysis
Despite these advances, significant challenges remain for advancement of this field of neuroscience
Seung on Twitter: @Sebastian Seung
Seung HS (2009). Reading the book of memory: sparse sampling versus dense mapping of connectomes. Neuron, 62 (1), 17-29 PMID: 19376064
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