The cyclic AMP(cAMP)-response element-binding protein(CREB)family of transcription factors is crucial for long-term memory(LTM)formation,and an interlinked positive and negative feedback loops of transcriptional regulation by activator CREB1 and repressor CREB2 are described in a minimal model for the induction of long-term memory developed by Song et al.In this work,5-HT as an important extracellular stimulus is added into the minimal model to examine dynamical properties of the gene regulatory network.And also,positive feedback as an essential factor for bistability could play more important role in inducing a high state of [CREB1] for the establishment of long-term memory.Thereby,by means of codimension-1 and 2 bifurcation analysis,we illustrated how the stimulus 5-HT and the positive feedback strength commonly generate diverse complex dynamics including monostability,bistability,and oscillations.Furthermore,comparative analysis of deterministic and stochastic dynamics resulted from the finite number of molecules reveals that deterministic bifurcations predict stochastic behaviors due to fluctuating copy numbers of molecular species,and the number of CREB1 molecules more and more preferentially resides near the high steady state,contributing to long-term memory formation,with increasing [5-HT].