Synapse structure varies across species

The New York Times covers new research which has found significant cross-species variation in the structure of the synapse – the chemical ‘connection points’ that allow neurons to communicate.

The study itself has been published in Nature Neuroscience and the full text is available online for those who want the in-depth science.

A whole new dimension of evolutionary complexity has now emerged from a cross-species study led by Dr. Seth Grant at the Sanger Institute in England.

Dr. Grant looked at the interconnections between neurons, known as synapses, which until now have been regarded as a standard feature of neurons.

But in fact the synapses get considerably more complex going up the evolutionary scale, Dr. Grant and colleagues reported online Sunday in Nature Neuroscience. In worms and flies, the synapses mediate simple forms of learning, but in higher animals they are built from a much richer array of protein components and conduct complex learning and pattern recognition, Dr. Grant said.

The finding may open a new window into how the brain operates. “One of the biggest questions in neuroscience is to answer what are the design principles by which the human brain is constructed, and this is one of those principles,” Dr. Grant said.

The paper itself doesn’t mention the issue, but I wander what implications this might have for the generalisation of animal experiments to humans.

The majority of cellular-level neuroscience research is done on animal tissue. While some of this focuses on the molecular level, where differences in the structure of, let’s say, ion channels, would be easily apparent in comparison to humans, some studies simply look at the ‘synapse’ as the smallest functional unit.

In fact, a considerable amount of neuroscience research is done on the 1mm long microscopic worm C. elegans and the fruit fly, drosophila. This new research suggests that neuroscientists may need to be additionally cautious when assuming that the findings relate to general laws that might apply in humans.

UPDATE: Neurophilosophy has a great write-up of this study, which discusses it in more detail.

Link to NYT article ‘Brainpower May Lie in Complexity of Synapses’.
Link to PubMed entry for scientific paper.
Link to full text.

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