Research reportIncrease of spike-LFP coordination in rat prefrontal cortex during working memory

•The spikes-LFPs coordination levels were measured by joint entropy indexes (JEIs).•Investigations of the JEIs changes in rat mPFC during a Y maze working memory task.•The spikes-theta JEI levels significantly increased during the correct trials.•Increases were also found in the JEIs of spikes-low gamma and spikes-high gamma.•Spikes-LFPs couplings may play a role in the working memory tasks.

Working memory (WM) refers to the short-term maintenance of information with higher cognitive functions. Recent researches show that local field potentials (LFPs) and spikes, as different modes of neural signals, encode WM, respectively. There is a growing interest in how these two signals encode WM in coordination. The aim of this study is to investigate spike-LFP coupling coding of WM via the joint entropy analysis. The experimental data were multi-channel spikes and LFPs obtained from SD rat prefrontal cortex through the implanted microelectrode array during the WM tasks in Y-maze. The short-time Fourier transform (STFT) was applied to analyze the power changes of WM related frequency bands in the LFPs. The joint entropy indexes (JEIs) between spikes and the principle components of LFPs were calculated for each pair of the spike and the LFP series during WM. The results showed that the power of theta (4-12 Hz), low gamma (LG, 30-60 Hz) and high gamma band (HG, 60-100 Hz) in LFPs increased during the WM tasks. In addition, the JEIs between spikes and LFPs components (theta, LG and HG) significantly increased in the correct trials. Besides, the coupling levels were low when the rats waiting in the starting area. These results suggest that the JEIs between spikes and LFPs components (theta, LG and HG) encode WM effectively. These findings could lead to improved understanding of the WM mechanism from the view of spike-LFP joint encoding.