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Circuits constructed from identified Aplysia neurons exhibit multiple patterns of persistent activity
D Kleinfeld1, F Raccuia-Behling, H J Chiel
1Solid State and Quantum Physics Research Department, AT&T Bell Laboratories, Murray Hill, New Jersey 07974.
Biophysical Journal
|April 1, 1990
Summary
Two-neuron circuits in Aplysia exhibit bistable activity, switching between states with external input. This demonstrates how simple neuronal networks can generate persistent activity patterns, crucial for understanding neural control.
Area of Science:
- Neuroscience
- Computational Neuroscience
- Cellular Neuroscience
Background:
- Neural circuits generate complex behaviors through persistent activity.
- Bistable neural networks, capable of maintaining two distinct activity states, are hypothesized to underlie memory and decision-making.
- Understanding the fundamental properties of simple neural circuits is essential for deciphering more complex brain functions.
Purpose of the Study:
- To construct and analyze simple in vitro neuronal circuits capable of bistable output.
- To investigate the mechanisms underlying bistability in neuronal networks.
- To explore how external inputs and background currents control the stability of neuronal activity.
Main Methods:
- Utilized identified neurons from the abdominal ganglion of Aplysia (L10, LUQ, L7, L12).
- Constructed two distinct two-neuron circuits in vitro: one inhibitory (L10-LUQ) and one excitatory (L7-L12).
- Analyzed circuit output states and their transitions in response to brief external stimuli and varying injected background currents.
Main Results:
- Both constructed circuits exhibited bistable output, with two distinct persistent activity patterns.
- Activity states could be switched by brief external inputs.
- Bistability was dependent on the nonlinear firing properties of individual neurons and network feedback, with a defined range of background currents supporting this phenomenon.
- Deviations from this current range resulted in single stable states.
Conclusions:
- Simple two-neuron circuits can exhibit bistable activity, supporting theoretical models of neuronal network function.
- The findings suggest mechanisms for generating stable output patterns in vivo and how command neurons might regulate circuit activity.
- This work provides a foundation for understanding how minimal neuronal components can produce complex dynamic states relevant to higher neural functions.