Fig 1.
Spectral analysis of spontaneous cyclic alternations of cortical brain state under urethane anesthesia.
A) 28.5 minute traces from the nCTX and HPC both early (starting 16 minutes) into the recording and late (starting 172 minutes) into the recording, depicting the spontaneous cyclic alternations seen in urethane anesthesia. Highlighted gray regions indicate the cycles used in Fig 2B. B) Spectrographic representation of the nCTX trace as shown in panel A. The most evident fluctuations were seen at ~1 Hz (indicated by the white dashed line). Alternation between states are indicated by the black dashed lines. C) Plot of 1 Hz power from the nCTX spectrograms (Panel B white dashed line) show cyclic fluctuations in amplitude corresponding to the transition between states. Deactivated states are denoted by the blue background, while activated states are denoted by the red background. D) Differing state change dynamics between the activated to deactivated and deactivated to activated state. Traces are taken form the 1 Hz power trace from the nCTX (Panel C). Selected period was from halfway through the proceeding activated state to halfway through the subsequent activated state. Time of 0 minutes was defined as time of transition form the deactivated to activated state. Transitions from the activated to deactivated sate were characterized by a more gradual variable transition, whereas transitions from the deactivated to active state were characterized by a rapid transition. Traces from the early in the recording are noted in black, whereas traces from the end of the recording are noted in grey.
Fig 2.
Spontaneous cyclic alternations of brain state under urethane anesthesia.
A) Power analysis of the nCTX shows low voltage, higher frequency activity in the activated state both early (36 minutes) into the recording (dark red) and late (184 minutes) into the recording (light red). The HPC shows a strong peak corresponding to theta activity associated in the activated state both early (dark red) and late (light red) in the recording. Power analysis of the nCTX in deactivated shows a high voltage low frequency activity, associated with slow oscillations both early (43 minutes) into the recording and (dark blue) and late (190 minutes) into the recording (light blue) in the recording. The HPC shows high voltage, low frequency activity in the deactivated both early (dark blue) and late (light blue) in the recording. No major changes in power analysis is noted across states in both the nCTX and HPC in comparison of early and late recordings. Three second traces from the nCTX and HPC in both activated (red) and deactivated (blue) states are inserted in the corresponding power analysis. Early activated (36 minutes) in dark red and deactivated (43 minutes) in dark blue are the top traces. Late activated (184 minutes) in light red and deactivated (190 minutes) in light blue are the bottom traces. B) 9.5 minute trace of the nCTX (top) and HPC (bottom) early highlighting one cycle both (starting at 35 minutes into the recording) and a 10.5 minute trace of the nCTX (top) and HPC (bottom) late highlighting one cycle (starting 181 minutes into the recording). Lines and arrows indicate the location of the three second excerpts and where power analysis was taken for each state.
Fig 3.
Stability of the spontaneous cyclic alternations in urethane anesthesia.
A) The average period length (hollow circles) of individual experiments ranging in time from 110–250 minutes. Overall average period length (8.87±0.64 minutes) (solid circle) for all experiments. B) Percentage of REM-like activity relative to total period length for individual experiments (hollow circle) and overall experiments (65.6±0.02% REM-Like activity) (solid circle). C) Scatter plot showing period length as a function of time for a single experiment lasting 200 minutes. Linear regression line is shown in red and is not significantly different from zero (p = 0.8757), indicating the period length did not change throughout the experiment. Only 1 experiment had slopes significantly different from zero. D) Scatter plot of the percentage of REM-like activity relative to total period length for a single experiment. In this experiment, slope was significantly different than zero (R squared = 0.2953, p = 0.0133), however, this is the only experiment in which the percentage varied significantly with time.
Fig 4.
Stability of breathing rate under urethane anesthesia.
A) Extraction of peak frequency of peak breathing rate during the first 40 minutes (left) and last 40 minute (right) of a 200-minute recording session. Deactivated states are indicated by the blue background, and activated states are indicated by the red backgrounds. Breathing rate remained stable and did not decrease as heart rate did. Fluctuations corresponding to activated and deactivated states remain stable throughout the recording session. Note the increase variance during the activated state. B) Spectrographic analysis of breathing rate showing the first 40 minutes (left) and last 40 minutes (right) of a 200 minute recording session. Fluctuations between activated and deactivated are indicated by black dashed lines. Fluctuations were primarily seen at ~2.0 Hz (120 breaths per minute). C) Overall average breathing rate for the activated (red circle) (2.00 ± 0.040 Hz) and deactivated (blue circle) (1.67 ± 0.048 Hz) states for all experiments. A 0.32 Hz (95% CI: 0.27 to 0.37 Hz) decrease was seen between the activated and deactivated state, this difference is significant (t(59) = 14.06, p < 0.0001). Dot and lines show all transitions. D) Activated (red) and deactivated (blue) breathing rates plotted against time for a single experiment with their respective linear regressions. Neither deactivated nor activated breathing rate different significantly from zero (p = 0.9540, p = 0.3478). Note the greater variation of breathing rate within the activated state (CoV, activated = 0.045±0.0054, CoV, deactivated = 0.024±0.0030, t(59) = 4.56, p<0.0001). E) The breathing rate of the activated (red) and deactivated (blue) states as a function of time for all experiments.
Fig 5.
Stability of heart rate under urethane anesthesia.
A) Extraction of peak frequency of peak heart rate during the first 40 minutes (left) and last 40 minutes (right) of a 200 minute recording session. Deactivated states are indicated by the blue background, and activated states are indicated by the red backgrounds. While fluctuations corresponding to activated and deactivated remain, the heart rate decreased throughout the recording period. B) Spectrographic analysis of heart rate showing the first 40 minutes (left) and last 40 minutes (right) of a 200 minute recording session. Fluctuations between activated and deactivated are indicated by black dashed lines. Fluctuations were primarily seen at ~8.6 Hz (516 beats per minute). C) Overall average heart rate for the activated (large red circle) (7.60±0.17 Hz) and deactivated (large blue circle) (7.42±0.17 Hz) states for all experiments. A 0.17 Hz (95% CI: 0.1381 to 0.206100) decrease was seen between activated and deactivated, this difference was significant (t(59) = 9.04, p < 0.0001). Dot and lines show all transitions. D) Activated (red) and deactivated (blue) heart rates plotted against time for a single experiment with their corresponding linear regressions. Activated heart rate was significantly different then zero (R squared = 0.2070, p = 0.0383) as well as the deactivated heart rate being significantly different from zero (R squared = 0.6276, p<0.0001). E) The heart rate of the activated (red) and deactivated (blue) states as a function of time for all experiments.