Metasegmental motor neurons

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Figure 1. Schematic representation of the Aplysia body, divided to illustrate target regions of pedal ganglia nerves. Modified from Hening et al, 1979.

Figure 2. Schematic representation of the dorsal Aplysia pedal and pleural ganglia. Left pedal ganglion shows designated sectors, right pedal ganglion shows approximate locations of identified neurons. Modified from Hening et al 1979.

Anatomy and Location

Metasegmental cells were 70-120um in diameter with indistinct pigmentation. Most were found to be located in anterior sector II, although some were also seen scattered throughout sector II (Fig. 2).

Motor effects and electrophysiology

About half of the metasegmental neurons were reported to cause longitudinal contraction, while the other half caused transverse effects. Both showed varying input after tail stimulation (Fig. 3), although head stimulation causes all metasegmental neurons to become excited.

Figure 3. Metasegmental motor neuron bursting contributes to locomotion. Tension recordings of metasegment contraction shows correlation with metasegmental motor neuron bursting initiated by exposure of tail to sodium crystals (indicated black bar). Modified from Hening et al 1979.

References

1. Hening, W.A., Walters, E.T., Carew, T.J., Kandel, E.R. (1979) Motorneuronal control of locomotion in Aplysia. Brain Research, 179. 231-253.