Category: Brain

Benjamin Wilhelm and colleagues the University of Göttingen Medical Center have developed a detailed 3D model of a synapse.  Millions of nerve terminals from rat brains were isolated.  A combination of electron microscopy, mass spectrometry, antibody staining, and super-resolution fluorescence microscopy determined the abundance and distribution of 62 proteins crucial for the synaptic vesicle cycle.

“Our model shows that the proteins involved in neurotransmitter release can be enormously abundant, with up to 27,000 copies per synapse,” said Professor Silvio Rizzoli, “whereas proteins involved in recycling are present in only 1,000-4,000 copies.”

The numbers of proteins involved in recycling are much lower than expected. They give the terminal the capacity to recycle 10% of its entire vesicle pool.  Recycling takes place slowly, in the seconds following vesicle fusion, therefore does not contribute when multiple vesicles fuse in quick succession.  As Rizzoli describes the advantage, “the cell does not need to produce huge numbers of recycling proteins, which saves energy.”

The model also shows that the proteins involved in the same steps of the vesicle cycle are present in roughly equal amounts within the terminal, raising the question of how their synthesis is regulated so that each set of proteins is present at the right concentration.

The researchers hope are to generate a similar model of an entire neuron within the next five years.

University of Adelaide researchers have grown brain-resembling cells from stem cells taken from teeth, potentially impacting stroke therapies.

According to Kylie Ellis, lead author of the study, “What we developed wasn’t identical to normal neurons, but the new cells shared very similar properties to neurons. They also formed complex networks and communicated through simple electrical activity, like you might see between cells in the developing brain.”

The stem cells expressed neuronal cytoplasmic proteins, neurotransmitter-specific markers, and functional voltage-gated L-type Ca²⁺ channels, but not spontaneous action potentials.

MIT‘s Kwanghun Chung and Stanford‘s Karl Deisseroth‘s CLARITY allows researchers to see directly into optically transparent whole brains or thick blocks of mouse brain tissue.

 Such studies in living people are impossible, because most neuron-tracing methods require genetic engineering or injection of dye in living animals.

The hope is that this will one day lead to a way to help people with severe mental illness or brain diseases.

Applying CLARITY to whole mouse brains, the researchers viewed fluorescently labeled neurons in areas ranging from outer layers of the cortex to deep structures such as the thalamus. They also traced individual nerve fibers through 0.5-millimetre-thick slabs of formalin-preserved autopsied human brain — orders of magnitude thicker than slices currently imaged.

In her roadmap, Georgia Tech professor Jennifer Hasler emphasizes analog processing’s key role in neuromorphic systems, specifically field programmable analog arrays.  She claims Georgia Tech’s FGAAs “award the programmability and capability of the Anadigm components” by housing “hundreds of thousands of programmable parameters, enabling them to be used for system level computing, not just analog glue logic.“

Hasler believes the path to desktop neuromorphic systems will require analog system-on-chip approaches to achieve the low power devices necessary to emulate billions of brain-like neurons connected by trillions of learning synapses.  She predicts that desktop neuromorphic systems that rival the compactness of the human brain will require a 100 million times reduction in power over the digital supercomputers simulating them today.