This paper considers two-dimensional model neurons of the form \( v' = F(v)-w+I\), \( w' = a(bv-w)\) for appropriate functions \(F\), with the rule that once \(v\) reaches a threshold it is reset to a lower value, and \(w\) is instantaneously incremented by a constant amount. The authors analytically determine conditions under which such a system possesses a globally stable periodic orbit. They demonstrate their results using three previously published neuron models.