The Mauthner cell: What has it taught us?

The Mauthner cell (M-cell) is one of the few identifiable neurons in the vertebrate central nervous system. The ability to locate the M-cell, along with its inputs and outputs, has resulted in important findings in diverse areas of neurobiology including the molecular biology of neurons, synaptic and systems physiology, behavior, development, and neuroethology. The review provides a brief overview of the M-cell and then focuses on recent studies applying state-of-the-art techniques to address new issues and revisit old ones. One advantage of this preparation is the ability to conduct multidisciplinary studies from the subcellular to behavioral levels. For example, studies of activity-dependent changes in the strength of mixed electrotonic and chemical synapses on the M-cell's lateral dendrite in vivo have been correlated with changes in the probability of eliciting a fast startle response initiated by the M-cell and its associated circuits. Similarly, it is now possible to image the activity of the M-cell and its homologs while observing motor behavior in zebrafish larvae. These approaches will provide direct tests of the functional properties of complex neural networks. Moreover, molecular mechanisms that underlie neuronal development can be tested directly with this neuron and its segmental homologs, because these cells occur in singular pairs at defined locations. Finally, after spinal cord injury, the M-cell's axon regenerates, but does not follow its original course, and the startle response gradually recovers. The accessibility of the M-cell system offers the promise that strategies employed in restoring the function of a neural network will be revealed. Thus, we anticipate that the M-cell system will become a favored preparation for multidisciplinary studies on the neuronal basis of behavior and the recovery of behavior after injury.