Circuits constructed from identified Aplysia neurons exhibit multiple patterns of persistent activity

Area of Science:

• Neuroscience
• Computational Neuroscience
• Cellular Neuroscience

Background:

• Neuronal circuits exhibit persistent activity crucial for memory and decision-making.
• Understanding the fundamental properties of bistable neuronal networks is essential for deciphering complex neural computations.

Purpose of the Study:

• To investigate the conditions under which simple neuronal circuits can generate bistable activity.
• To analyze how feedback connections and individual neuron properties contribute to network stability.
• To explore the potential for external inputs to control these bistable states.

Main Methods:

• Construction and in vitro analysis of two-neuron circuits using identified neurons from Aplysia abdominal ganglion.
• Coculturing specific neuron pairs (L10-LUQ with inhibitory connections, L7-L12 with excitatory connections).
• Recording and analysis of neuronal firing patterns and network output states under varying injected currents.

Main Results:

• Both circuits exhibited two stable patterns of persistent activity (bistability), switchable by brief external input.
• Inhibitory L10-LUQ circuit showed alternating activity states, while excitatory L7-L12 circuit showed quiescent and continuously firing states.
• Bistability depended on neuronal nonlinearities and feedback, with a defined range of background currents for stability.

Conclusions:

• Simple two-neuron circuits can replicate bistable output states hypothesized for larger neuronal populations.
• The findings provide insights into how in vivo circuits generate stable activity patterns and how higher centers may exert control.
• This work validates theoretical models of neuronal network dynamics using experimental preparations.