An article in the November issue of Mind by B. Reiner about the progress in creating meditation by stimulating parts of the brain, Secrets of How Meditation Works, has an interesting pointer to fast-spiking interneurons:

From the perspective of neuroscience, meditation can be characterized as a series of mental exercises by which a person strengthens control over the workings of his or her own brain. The simplest of these practices is focused attention, during which one concentrates on a single object or experience—say, one’s breathing. … But focused-attention meditation is fairly basic compared with the kind of contemplation conducted by experienced Buddhists. Called open-monitoring meditation, this advanced method is, in many ways, a form of metacognition—the objective is not to focus one’s attention but rather to use one’s brain to monitor the universe of mental experience without directing attention to any one task. … the long-term meditators’ brain waves were in sync at unusually high speed. Brain waves, … occur at different speeds … Gamma waves are the fastest of the bunch, and in normal people they happen only in very short bursts during REM sleep and, rarely, waking cognition. The Davidson study was remarkable in that it showed that long-term meditators are able to produce sustained gamma activity in a manner that had never been previously observed in a human being. As such, sustained gamma activity emerged as a proxy for at least some aspects of the meditative state. … (In studies in Nature C. Moore, L. Tsai and K. Deisseroth) confirmed the hypothesis that gamma rhythm results from the activation of fast-spiking interneurons, so named because they fire at a higher than normal rate and have short, local connections within the cerebral cortex. … In addition, abnormal gamma synchronization is a hallmark of disorders such as autism and schizophrenia, and it may contribute to altered cognition in these and other mental illnesses.