oscillation power in the lateral entorhinal cortex, which transmits various sensory inputs to the hippocampus and thus participates in memory processes analogous to those affected by human AD. Decreased hippocampal slow gamma power has also been observed in the 3xTg mouse model of AD. Gamma stimulation may have therapeutic potential for AD and other neurodegenerative diseases. Optogenetic stimulation of fast-spiking interneurons in the gamma wave frequency range was first demonstrated in mice in 2009. Entrainment or synchronization of hippocampal gamma oscillations and spiking to 40 Hz via non-invasive stimuli in the gamma frequency band, such as flashing lights or pulses of sound, reduces amyloid beta load and activates microglia in the well-established 5XFAD mouse model of AD. Subsequent human clinical trials of gamma band stimulation have shown mild cognitive improvements in AD patients who have been exposed to light, sound, or tactile stimuli in the 40 Hz range. However, the precise molecular and cellular mechanisms by which gamma band stimulation ameliorates AD pathology is unknown. Fragile X syndrome Hypersensitivity and memory deficits in Fragile X syndrome may be linked to gamma rhythm abnormalities in sensory cortex and hippocampus. For example, decreased synchrony of gamma oscillations has been observed in auditory cortex of FXS patients. The FMR1 knockout rat model of FXS exhibits an increased ratio of slow (~25-50 Hz)to fast (~55-100 Hz) gamma waves. Meditation High-amplitude gamma wave synchrony can be self-induced via meditation. Long-term practitioners of meditation such as Tibetan Buddhist monks exhibit both increased gamma-band activity at baseline as well as significant increases in gamma synchrony during meditation, as determined by scalp EEG. fMRI on the same monks revealed greater activation of right insular cortex and caudate nucleus during meditation. The neurobiological mechanisms of gamma synchrony induction are thus highly plastic. This evidence may support the hypothesis that one's sense of consciousness, stress management ability, and focus, often said to be enhanced after meditation, are all underpinned by gamma activity. At the 2005 annual meeting of the Society for Neuroscience, the current Dalai Lama commented that if neuroscience could propose a way to induce the psychological and biological benefits of meditation without intensive practice, he "would be an enthusiastic volunteer." See also Brain waves Delta wave – (0.1 – 3 Hz) Theta wave – (4 – 7 Hz) Mu wave – (7.5 – 12.5 Hz) SMR wave – (12.5 – 15.5 Hz) Alpha wave – (7 (or 8)