Figure 5
Electrically induced N2 during awake state is similar to the downstate of spontaneous slow waves (SWd) during sleep. (a) LFP; (b) CSD; (c) MUA; (d) TFR. Row 1: Laminar profile of the spontaneous SW time locked to the downstate (trial-average of Pt1). The downstate is characterised by upper layer surface negativity (a), a middle layer source (b) accompanied by a marked decrease in multiunit activity (c) in the same layers, and a broadband power decrease (d) through all cortical layers. Row 2: Laminar analysis of CCEP in awake state (trial-average of Pt1). LFP shows a superficial negativity during the N2 (a). CSD distribution shows an upper-middle layer source during the time of N2 (b). MUA is decreased during N2 in middle cortical layers (c). The TFR shows a wide-band spectral power decrease through all cortical layers during N2 (d). Note the time scale differences between the two analyses (− 250–1000 ms for the N2 and − 1000–1000 ms for the SWd). Red arrows indicate the time of stimulus. Row 3: Statistical comparison of SWd and N2 characteristics based on Pearson’s r correlation method (For LFP r = 0.92, CSD source r = 0.75, MUA r = 0.79, TFR r = 0.41, p < 0.05). The different color dots indicate individual electrode contacts. The warm color dots are for contacts located in superficial layers, the cold color dots indicate electrodes from deep layers (see color bar). The zero value means there is no detectable SWd or N2 component on that channel. All data are derived from Pt1. (e) Averaged SWd (top) and N2 (bottom) waveforms (Pt1) on selected channels (marked in left corner of the plots) of low-pass filtered LFP and associated MUA recordings presenting the characteristic period of neural silence. Note the different amplitude and time scales applied in case of averaged waveform plots. (f) Overlay of SWd (grey curves) and N2 (black curves) averaged waveforms (Pt1). LFP (top) is derived from layer I-II, while the CSD (bottom) from layer III recordings (corresponding to the layers of maximal event amplitudes). Stimulation preceding N2 is marked with a dashed line.
