Figure 2

(a) Full-power spectrum expressed in heat maps in fronto-parieto-occipital cortical areas during each 15-min block of the 2-h post-administration of ketamine (2.5, 5, 10 mg kg⁻¹). Only right hemisphere locations along the antero-posterior axes were presented (frontal right ‘FR’, parietal right ‘PR’, occipital right ‘OR’, see red dots on the brain diagram). Changes in color from cold dark blue to warm red color indicate an order increase in the magnitude of oscillatory power. (b) Changes in gamma power during the first 2-h post-administration of ketamine. Color coded bars underneath the curves indicate intervals in which oscillatory activity differed from vehicle (mixed-model design ANOVA). (c) Locomotor activity during the first 2-h post-administration of ketamine. (d) Spearman correlations (upper panels) at 30-min after the administration of ketamine between the gamma oscillations and locomotor activity and (lower panels) Spearman’s rank correlation coefficients (R-values) plotted for each time block of 15-min. (e) Time course of phase–amplitude cross-frequency coupling (CFC) for pre- and post-administration of vehicle and of ketamine (2.5, 5, 10 mg kg⁻¹). The comodulograms show coupling strength between the phase of theta frequency and the amplitude of high-gamma activity. During baseline period, phase–amplitude coupling (PAC) was observed between theta (5 Hz) and high-gamma (100 Hz). Ketamine at the 5 and 10 mg kg⁻¹ elicited a shift in the modulation index (MI) of phase-frequency coupling from theta towards delta and an increase in the strength of MI in broadband from 60–150 Hz with the strongest modulation occurring in the tie interval 30–60 min. MI data are presented as means values in the frontal right structures.