Prosegmental motor neurons

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Prosegmental motor neuron activity causes movement in the anterior segment of the animal (Fig. 1).

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

Prosegmental motor neurons typically have small (40-80um) and non-distinctive soma. Most soma of prosegmental motor neurons were located in sector II, with a few also found in Sector Ia. The soma were primarily clustered around the pedal connective innervating each sector (Fig. 2).

Motor effects and electrophysiology

Prosegmental motor neurons can be further divided in to three subclasses based on their motor effects.

  • Dorsoventral (transverse) contractors causing lateral tegument constriction transversely.
  • Longitudinal contractors causing lateral tegument constriction longitudinally.
  • Longitudinal contractors causing anterior dorsal neck contraction.
Figure 3. Prosegmental motor neuron bursting contributes to locomotion. Tension recordings of transverse contraction of prosegment shows tension increasing after electrical pulse to right posterior pedal nerve (indicated black bar) initiates bursting in a prosegmental motor neuron. 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.