Article Figures & Data
Figures
- Figure 1.
Extensive variability of evoked response magnitude and spontaneous EEG power during a 28-min continuous recording session. A, Twenty seconds of raw EEG data from an individual rat. Arrows denote electrical stimulation to produce an evoked response. B, A typical evoked response. To quantify the evoked response, fEPSP slope is calculated within the bracketed region while PS amplitude (solid gray line) is the amplitude from response trough to the tangent line connecting response peaks (dotted line). C, Power spectrum of spontaneous EEG activity from the 4-s shaded region in A. D, Average evoked response from all 420 stimulations during a recording session in a single rat. E, Extensive variability in the evoked response is observed in both the fEPSP slope (top) and PS amplitude (bottom). F, The power spectrum of SBA averaged across all 4-s epochs of the recording session. Power spectra were calculated from 0.5 to 100 Hz but are only depicted to 40 Hz here for enhanced visualization. In D, F, dark shaded regions encompass the middle 50% of all observed values and light shaded regions encompass 95% of all observed values. Similar variability in both evoked responses magnitude and EEG power was observed when the stimulation frequency was 0.10 Hz instead of 0.25 Hz (see Results).
- Figure 2.
Correlations between antecedent EEG power and fEPSP slope (A) or PS amplitude (B) at stimulation frequencies of either 0.25 or 0.10 Hz. Heat maps depict correlations for each animal for each frequency bin while reported r values reflect the average r value observed across all rats. Low- and high-frequency BLP and fEPSP slope are negatively correlated while these same frequency bins are positively correlated with PS amplitude. PS amplitude could not be consistently quantified for rat 7 or 17. For frequency bin labels, G = γ; B = β.
- Figure 3.
fEPSP slope (A) and PS amplitude (B) as a function of preceding low-, middle-, or high-frequency BLP quartiles and stimulation frequency (0.25 or 0.10 Hz). C, Average evoked responses from an individual rat for responses following spontaneous EEG epochs that contained the least (black) and most (gray) BLP for each condition.
- Figure 4.
Phase-locking of EEG BLP, fEPSP slope, and PS amplitudes. A, Average power spectra (n = 17 rats) of low-, middle-, and high-frequency BLP during the entire recording session. Insets, Autocorrelograms for infraslow-filtered high- and low-frequency BLP. Gray dotted lines depict 95% confidence intervals. B, Spontaneous fluctuations in evoked response magnitude and EEG BLP are evident in infraslow filtered time series data from a single rat. C, IPDs calculated at each data point across the time series data depicted in B. Each gray arrow represents the phase difference calculated at a single time point. fEPSP and low-/high-frequency BLP are typically out of phase (π radians), while PS amplitude and low-/high-frequency BLP are typically in phase [0(2 π) radians]. No clear phase locking is present between middle-frequency BLP and fEPSP slope or PS amplitude.
- Figure 5.
IPD between low-frequency (A, B), middle-frequency (C, D), and high-frequency (E, F) BLP and fEPSP or PS for rats stimulated at 0.25 Hz (similar phase distributions were observed for 0.10 Hz stimulated rats). Dark bars depict the distribution of actual observed phase differences while light bars depict the distribution of phase differences observed between BLP and shuffled fEPSP or PS data. fEPSP slopes are predominantly antiphase with high/low BLP, while PS amplitudes are predominantly in phase with high/low BLP. Insets depict the distribution of PLFs calculated between BLP and shuffled fEPSP or PS data (histogram), the 0.05 critical value obtained from these distributions (dotted line), and the PLF calculated from observed data (solid gray line). PD = circular mean phase difference ± circular SD. Phase locking: *p < 0.05, ^p < 0.10.
- Figure 6.
fEPSP slope (A) and PS amplitude (B) vary as a function of the phase of infraslow fluctuations in low- and high-frequency BLP but are not significantly altered by infraslow changes in middle-frequency BLP. C, The opposing effects of infraslow BLP phase on fEPSP slope and PS amplitude produce variations in EPSP-PS coupling across infraslow cycles in rats stimulated at either 0.25 Hz (top row) or 0.10 Hz (bottom row). Dotted lines depict unitary EPSP-PS coupling at all phases, and gray regions depict observed coupling (regions that exceed dotted lines indicate stronger EPSP-PS coupling than average, while regions that do not reach dotted lines indicate weaker EPSP-PS coupling). Scale bar represents a change of 10% of the mean EPSP-PS coupling.
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