Putative inhibitory neurons located in layer I of cortex. They make up between 10 and 15% inhibitory cells in that most superficial layer. Story here, courtesy of SCIENCE.
What is interesting is that these cells are not found in mouse brain as determined by single nucleus RNAseq. Which raises the question about whether these cells are important to human-level higher cognition.
Link to the original paper in Nature Neuroscience here.