December 16, 2020
Light and electron micron microscopy representations of a neuron showing synapses

Multiphoton imaging in vivo provides measures of synaptic activity and function (left), while electron microscopy (right) performed on the same neuron provides structural information at the nanometer scale. Image credit: Max Planck Florida Institute for Neuroscience

A common analogy used to describe the brain is that it consists of tiny interconnected computers. Each one of these computers, or neurons, process and relay activity from thousands of other neurons, forming complex networks that allow us to perceive our surroundings, make decisions, and guide our actions. Communication between neurons occurs through tiny connections called synapses, and each neuron integrates the activity across these synapses to form a single output signal. However, not all synapses are created equal. Synapses converging onto an individual neuron differ in size, and size is correlated with strength: larger synapses are stronger and have a greater influence on a neuron’s output than smaller synapses. 

Now, for the first time, an interdisciplinary team of scientists at the Max Planck Florida Institute for Neuroscience (MPFI) report the results of a novel approach that allowed them to achieve measurements of the strength of connections between two neurons. Published in the journal Nature, their work demonstrates that synapse size is not correlated with response similarity and suggests neural response properties reflect the total number of active synapses, both weak and strong.