Watching While You Think and Learn

"With this method we can understand, in greater detail, how the human brain regulates complex thought processes and, for example, how it transforms the numerous sensory impressions into long-term memories" _MNT

The circuits of your brain trace complex paths across space and time. Understanding how brains think means understanding the spatial and temporal actions of the neuronal correlates of thought. Nature Methods has a recent (4Jan09) online report describing the use of a trio of genetically engineered viruses used to trace the activity of complex brain circuits.

In a recent paper in Nature Methods, the team describes the production and application of three types of transsynaptic viruses. The first class was engineered with differentially colored “bulbs” such that neural circuits can be lit up with all the colors of the rainbow. The second type of virus brings a small genetic clock into each infected cell in the circuit so that the elapsed time after virus entry can be recorded. The third class has the most intelligent nanotools. These viruses turn on a special fluorescent bulb in each neuron but only when the neuron is active. Using these tools, researchers can now “watch” the activity of many neurons simultaneously in identified, connected neurons of different brain circuits. _FMI

This work extends previous work using engineered viruses to act as trans-synaptic "ferries" of genes encoding for fluorescent proteins, to infect specific neurons along the path of a particular brain circuit. Such infected neurons along the circuit will subsequently "light up" like a light bulb when activated.

The protein complex was actually produced in the nerve cells of the "infected" mice and functions there as an calcium indicator: if the calcium level within a cell increases - which is the case with every action potential - the D3cpv changes form when it binds to calcium. As a result, the two fluorescent proteins, CFP and YFP, move closer to each other and the transmission of energy between the CFP and YFP changes.

"To observe this change, we use a two-photon microscope developed by Winfried Denk", explains Hasan. Each individual action potential that arises due to a stimulus makes itself directly perceivable in the brain through yellow illumination and the simultaneous reduction in the emission of blue light. The two-photon microscope pinpoints the coincidence between the two fluorescent signals very accurately and clearly reveals which nerve cells are communicating and exchanging information with each other and when. _MedNewsToday

Such methods of observing functioning brain circuits over a period of time should help in piecing together how the brain "thinks." Other tools such as special types of fMRI, MEG, nuclear medicine techniques such as PET and SPECT, etc. will further complete the overall picture, when correlated with psycho-neurological observations.

A reliable "lie-detector" would be a simple test of concept. As expertise with these methods of real-time brain tracing improves, a more subtle and sophisticated reading of minds will become possible.