  See all article types »  Gamma Rhythms in the Brain    •
Xiaoxuan Jia mail,     • Adam Kohn     • Published: April 12,
2011   • DOI: 10.1371/journal.pbio.1001045   Hans Berger first
successfully measured the brain waves of humans in 1924 using
the electroencephalogram (EEG) [1]. His goal was to demonstrate
that the electromagnetic fields of the human brain could be used
for telepathy. Although the signals he detected were
unsuccessful for this purpose, the EEG was widely adopted by
clinicians and scientists. This is because the recordings are
easy to perform and the rhythms detected are informative of
brain state. For example, when we are in a deep sleep, the EEG
consists of low-frequency, large-amplitude oscillations; when we
are awake and attentive, it consists primarily of fast, small
amplitude rhythms.  Brain rhythms are evident as extracellular
voltage fluctuations. These arise from summed electrical
activity (primarily, but not exclusively, inputs) in populations
of neurons, and are shaped by the geom