This study described a unique set of deep layer neurons in posterior parietal cortex (PPC) whose spiking activity is inversely correlated with all principal cells and interneurons in all brain states, but most commonly during the down state of non-REM (NREM) sleep. They identified down state-active (DSA) neurons as deep layer neocortical neurogliaform cells that express ID2 and Nkx2.1. For this study, several lines of transgenic mice for optogenetic tagging of the recorded units were used. All animals were implanted with 64-site silicon probes in the PPC. Ground and reference wires were implanted in the skull above the cerebellum and a grounded copper mesh hat was constructed, which shielded the probes. The dataset includes electrophysiology, behavioral, and immunohistochemistry data.