Functional dissection of circuitry in a neural integrator

Area of Science:

• Neuroscience
• Computational Neuroscience

Background:

• Neural integrators accumulate transient inputs into persistent neural firing rates, forming a basis for short-term memory.
• A common hypothesis suggests positive feedback via mutual inhibition between opposing cell populations underlies this persistence.

Purpose of the Study:

• To test the positive feedback hypothesis in the goldfish oculomotor velocity-to-position integrator.
• To investigate the role of mutual inhibition in neural integration mechanisms.

Main Methods:

• Pharmacological silencing of one of two opposing cell populations in the goldfish oculomotor integrator.
• Measurement of eye position and neural firing rates in the remaining population.
• Complementary experiments involving partial silencing of a single population.
• Development of network models incorporating synaptic-input thresholds.

Main Results:

• Induced neural firing drifts were confined to approximately half of the oculomotor range, contradicting predictions of the positive feedback hypothesis.
• Experimental data suggested an alternative role for mutual inhibition.

Conclusions:

• Mutual inhibition between opposing cell populations does not provide positive feedback for neural integration.
• Mutual inhibition serves to coordinate intrinsic persistent activity within each population, offering a new model for integrator function.