Optogenetic data reveal changes in gamma-band oscillations due to cocaine addiction*

Cocaine addiction is a significant healthcare issue. We investigated the effect of acute cocaine injection on the medial prefrontal cortex (mPFC) activity of mice. The study's main goal was to determine the changes in the gamma oscillations and their relationship to short-term neuroadaptation that may mediate addiction. The in vivo locale field potentials (LFPs) in response to a brief 10 ms laser pulse delivered to the mPFC were recorded for 2 s. For each of the 17 mice in the experiment, we repeated the optogenetic stimulation 100 times. Given the nonlinear nature of the mPFC network response and the nonstationarity of the recorded data, we used the empirical mode decomposition method to obtain orthogonal intrinsic mode functions (IMFs). The number of IMFs was selected such that the frequency bands of the decomposed signal do not overlap and they match the known brain wave frequency bands delta (0.5-4 Hz), theta (4-8 Hz), alpha (8-12 Hz), beta (12-35 Hz) and gamma (> 35 Hz). Our results showed significant changes in the gamma band between control and cocaine cases.