In neural systems, an electrical synapse is a mechanical and electrically conductive link between two adjacent neurons that is formed by proteins known as gap junctions. Hence, an electrical synapse is also called a gap junction. In this kind of coupling, the synaptic current is proportional to the difference of membrane potentials between a neuron and its neighbors. Classically, electrical synapses
can be thought to increase the speed and synchrony of neural activity.
Gap junctions allow direct communication between cells. They are typically formed from the juxtaposition of two hemi-channels (connexin proteins) and
allow the free movement of ions or molecules across the intercellular space separating the plasma membrane of one cell from another (see figure). The
synaptic delay for a chemical synapse is typically in the range 1 – 100 ms, while the synaptic delay for an electrical synapse may be only about 0.2 ms, that means that this type of connections are faster than chemical synapses. This type of connections are the responsible for the collective behavior of the network.
The presence of gap-junctional coupling in a neuronal network necessarily means that neurons directly “feel” the shape of action potentials from other neurons to which they are connected. It does not necessarily pave the way for tractable network studies.
The diversity of functional roles that electrical synapses is well known in the vertebrate retina, in which gap junctions play a crucial role in differential motion detection, approaching motion detection. The networks formed by electrically coupled neurons are plastic and reconfigurable, and those in the retina are positioned to play key role and diverse parts in the transmission and processing of visual information.
