Theta rhythm is considered to play a critical role in spatial and nonspatial mnemonic functions of the limbic system. The anterior thalamic nuclei, a central component of Papez’ circuit, form the core of an “extended hippocampal system” that is vital for memory. The nucleus reuniens, the largest of the midline nuclei of the thalamus, has been neglected in contemporary neuroscience, despite being a major source of thalamic afferents to the hippocampus and parahippocampal structures. Moreover, there are suggestions that it plays key roles in memory consolidation. In both anteromedial and reuniens thalamic nuclei, in freely moving rats, we have recorded subsets of theta modulated cells that differ in terms of their electrophysiology. In anteromedial thalamic nucleus we detected bursting and non-bursting neurons that were strongly entrained by theta oscillations and synchronized their activity in the 6–11 Hz range. In nucleus reuniens we recorded theta modulated cells which show unusual pattern of firing. Except that the bursts of neuronal activity were strongly entrained by the theta rhythm they also phasically differed in their intensity.