Abstract: People have thought internal clock to be the basis of interval timing for a long time, and believe that the dopaminergic system (e.g. basal ganglia) is specially related to the speed of the internal clock. Evidences for this model have been accumulated from neuropharmacology studies and symptoms of patients suffered from the Parkinson’s disease. Recently, this model is challenged by data from delicately designed behavioral experiments, micro-electrode recordings, and even re-analysis of results which support the internal clock model. Researchers have provided various new models to take place of the internal clock model, and two of them (the neural state model and the energy expended model) are most important and successful.

Key words: timing cognition, brain mechanism, internal clock model, neural state model, energy expended model