The exponential periodicity and stability of continuous
nonlinear neural networks with variable coefficients
and distributed delays are investigated via employing
Young inequality technique and Lyapunov method.
Some new sufficient conditions ensuring existence and
uniqueness of periodic solution for a general class of
neural systems are obtained. Without assuming the
activation functions are to be bounded, differentiable
or strictly increasing. Moreover, the symmetry of the
connection matrix is not also necessary. Thus, we
generalize and improve some previous works, and they
are easy to check and apply in practice.