© 2020 IEEE. Studies have shown that the firing activity of single neurons in brainstem dorsal raphe nucleus (DRN) is linked to slow-wave oscillations in the cortex, especially the frontal cortex. However, most studies consist of either single DRN neuronal or single-channel electrocorticogram (ECoG) recording. Hence, it is unclear how a population of DRN neurons with electrophysiologically diverse characteristics can coordinate and relate to the oscillatory rhythms in different cortical regions. In this work, we explored the technical feasibility of such an investigation. We simultaneously recorded extracellularly a group of DRN neurons and three cortical regions using electrocorticogram (ECoG) in two anaesthetized SERT-Cre mice. The cortical regions were the two bi-hemispheric frontal and one (right) occipital regions. We then used coherence analysis to quantify the relationship between DRN neurons and cortical activity rhythms. We also computed the coherence between firing activities of DRN neurons to quantify their relationship. We found slow-firing DRN neurons with regular and irregular spiking characteristics, potentially serotonergic neurons, were more likely to have stronger relationships with cortical ECoG signals, especially the frontal cortex. Moreover, the DRN neurons were generally found to be weakly correlated with each other. Future investigation with more samples and analytical methods will be conducted to validate our results.