Some neurons have direct electrical connections with each other through what are known as gap junctions. Gap junctions are composed of proteins that cross the cell membranes of adjoining cells and enable current to flow between them. Recent studies have shown that gap junctions can help enable oscillatory activity amongst neurons but otherwise their contribution to specific processes in the brain remains unclear. The recent paper “Electrical Synapses Control Hippocampal Contributions to Fear Learning and Memory” (published January 7, 2011 in Science) reports that gap junctions can be an important factor in learning and memory.
Gap junctions are found between inhibitory (GABAergic) interneurons in the dorsal hippocampus and medial septum. These neurons drive hippocampal theta rhythms. Blocking gap junctions in the dorsal hippocampus disrupts theta rhythms and learning. The authors hypothesize that, since place cells fire in relation to the theta cycle, disrupting theta may abolish the temporal codes for locations. The role of gap junctions in signal processing has generally taken a back seat to chemical synapses. It’s exciting to see more information on the importance of gap junctions beginning to emerge.
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