A ‘mini-computer’ within the brain

American researchers have revealed new details as to how the human brain processes information that could entirely shift our understanding of the field. Their work suggests that ‘wires’ of the brain, dendrites, could in fact be far more active in information processing than previously thought. This research could point to intriguing new interpretations of the brain’s cytoarchitecture, as well as pointing towards new management of neurological disorders. The findings were published in Nature on the 27th October.

Dendrites are neural projections. Conventional wisdom has deemed these branch-like structures to be largely passive, involved in relaying information, but not involved in its processing. The work by Smith et al. has revealed that these projections actually work to significantly increase the computational capacity of the brain.   Dr Spencer Smith, assistant professor at the UNC School of Medicine, said “…it’s as if the processing power…is much greater than we had originally thought”.

This new study utilised patch clamp electrophysiology recordings carried out on mouse dendrites. This technique involves recording the activity of an electrically excitable cell via a glass microelectrode. Unfortunately, this is a fiddly process, and according to Smith “you have to do this blind. It’s like fishing but all you can see is the electrical trace of a fish…you just go for it and see if you can hit a dendrite. Most of the time you can’t.” The work was made easier when Smith developed his own two-photon microscope system for better resolution.

Using the patch-clamp cellular recording technique, the team recorded activity in dendrites within the brains of anesthetised and awake mice. They showed the animals visual stimuli on a computer screen while closely monitoring their brain activity. Surprisingly, there were bursts of activity in the ‘passive’ dendrites. These were not random, but occurred in combination with exposure to the stimuli. Furthermore, optical recording of calcium (involved in release of neurotransmitter molecules in synaptic signalling) revealed that during these periods of activity the dendrites alone were involved in electrical spiking, other parts of the neuron remained silent.

Dr Tiago Branco, modelled these findings mathematically, incorporating biophysical parameters; the model suggests that known mechanisms support the researchers’ observations. This mathematical model supports their findings and paves the way for future exploration of this new role for dendrites in the brain.

Further information at: http://news.unchealthcare.org/news/2013/october/unc-neuroscientists-discover-new-2018mini-neural-computer2019-in-the-brain