Threeneuron

Threeneuron is a term used in computational neuroscience to denote a minimal neural motif consisting of three interconnected neurons designed to illustrate how simple connectivity can yield a range of dynamic behaviors. It is not an anatomical structure but a conceptual unit used in modeling and education to study transient dynamics, synchronization, and rhythm generation in small networks.

In a common formulation, the motif comprises two excitatory neurons (E1 and E2) and one inhibitory neuron (I). Connections may include E1 → E2, E2 → I, and I → E1 and/or E2, with the possibility of E1 and E2 also projecting to I. This creates a small feedforward or feedback loop, and variants may swap excitatory with inhibitory roles or include mutual inhibition between E1 and E2. The exact wiring determines the qualitative behavior, such as stable steady states, oscillations, or transient bursts.

Dynamics: The three-neuron motif can support oscillatory activity when inhibitory feedback introduces a delay, and when synaptic strengths and time constants are balanced. Depending on parameters, the circuit may synchronize the two excitatory neurons, produce anti-phase firing, or generate short-lived activity sequences that depend on initial conditions.

Applications: Threeneuron motifs are used in theoretical analyses of motif-level dynamics, in teaching to demonstrate how network structure shapes function, and in the design of compact neuromorphic modules that mimic rhythmic processing.

See also: neural motif, triadic circuit, minimal circuit, neuromorphic engineering.