Power Law in the Brain

Marcel den Nijs
UW Physics

We report the results of our search for power-law scaling in electrical signals from the human brain, using subdural electrocorticographic recordings from the surface of the cortex. The power spectral density (PSD) of these signals follows power-law form P(f)~ f ^-x from 80 to 500 Hz. This scaling index x= 4.0 (0.1) is universal, across subjects, area in the cortex, and local neural activity levels. The shape of the PSD does not change with local cortex activity, only its amplitude increases. We observe a knee in the spectra at a frequency of 70 Hz, implying the existence of a characteristic time scale of order 2-4 msec. Below this knee we find evidence for a power-law with exponent x=2.0 (0.4) .  Web page.