Figure 3

(a) Full-power spectrum expressed in heat maps in fronto-parieto-occipital cortical areas during each 15-min time block after once daily chronic administration of ketamine (10 mg kg⁻¹). Only right hemisphere locations along the antero-posterior axes of the first day of each week (W) are displayed for (frontal right ‘FR’, parietal right ‘PR’, and occipital right ‘OR’). Changes in color from cold dark blue to warm red color indicate an order increase in the magnitude of oscillatory power. Note the increased higher gamma power following acute administration of ketamine was followed by a consistent shift in power towards slow alpha rhythm during repeated treatment. (b) Coherence indices over 0.5–100 Hz at 30-min after repeated administration of ketamine (2.5, 5 and 10 mg kg⁻¹) and vehicle. W1 and W4 indicate weeks 1 and 4 following repeated treatments. Ketamine decreased coherence in different oscillatory activities across all selected cortical pairs in comparison with that of the control group. (c) Functional network coherence changes from baseline in each frequency band of interest derived from consecutive 4-s epochs concatenated and averaged in 15-min. The width of the edges between pair electrodes is drawn proportional to the weight of changes in coherent activity during baseline session from baseline (0–50%, 50–100% and 100–150%). Red color represents increases and blue color indicates decreases. Average networks derived from the first recording session after ketamine treatment for each frequency band. Time-evolving dominant coherent activity in the frontal–parietal and occipital structures in δ/θ1 and α1 indicated the most persistent edges scaled to the frequency of the most common edge during waking in W1 and W4, respectively.