Increased sleep deprivation altered sleep patterns significantly during the first hour of the recovery period (). Compared to the 2 hour deprivation condition, there was significantly less time spent in wake and more time spent in LQS, DQS, and REM in the 4 hour and 6 hour deprivation conditions (p < 0.05). While the percent time spent in REM sleep increased with longer deprivation periods, it composed less than 15 percent of the total time. Consequently, there were too few stimuli present during REM, and the optical responses showed small signal-to-noise ratios. The data during waking states was convoluted with movement artifact, making the interpretation of the hemodynamic response difficult. Therefore, we focused our analysis on the LQS and DQS states. In the control condition, the total amount of time spent in wake and sleep did not significantly differ across the different time periods (). While we might expect to observe small time-of-day differences in sleep structure, the novel environment may have artificially increased the amount of waking these animals experienced over the recording period.
Figure 3 The percent time spent in each state for the first hour recovery period (A) from 4 animals shows that increased amounts of sleep deprivation caused a significant decrease in the percent time spent in wake (W) and a significant increase in the percent (more ...)
Two example traces are shown in from recordings conducted with no sleep deprivation. Evoked electrical responses showed larger P1 amplitudes during LQS and DQS compared to wake (, p < 0.05), as expected (Rector et al., 2009b
), at a 65 dBa stimulus intensity. The simultaneous evoked hemodynamic response peak amplitude was larger during LQS and DQS compared to wake (Schei et al., 2009
) (, p < 0.05).
Figure 4 Example evoked electrical response potentials (ERPs, A,B) and inverted evoked hemodynamic responses (C,D) from two animals recorded under no sleep deprivation conditions. We measured the ERP P1 and N1 amplitudes and the hemodynamic response peak and trough (more ...)
A plot of the ERP mean P1 and N1 amplitude from all 4 animals after sleep deprivation and control conditions, along with standard error, is shown in . There were no statistically significant within-state differences in the P1 and N1 amplitudes for LQS and DQS during the first hour recovery period following 2, 4, or 6 hours of sleep deprivation. shows the ERP P1 and N1 amplitudes for the no deprivation, control condition. The only difference we observed occurred between the second hour and sixth hour recording time periods where there was a small but significant decline in the ERP P1 amplitude (p < 0.05).
Figure 5 The evoked electrical response potential (ERP) P1 and N1 amplitudes across light quiet sleep (LQS) and deep quiet sleep (DQS) during the first hour recovery period measured from 4 animals showed no significant difference across deprivation hours (A). (more ...)
Two examples of the evoked vascular responses during LQS () and DQS () for the first hour recovery period show that the evoked vascular response became smaller for DQS with longer deprivation periods. We focused on the changes in the peak and trough amplitudes, indicated by the arrows, during LQS and DQS for the first hour recovery period following sleep deprivation. shows the average and standard error of the peak and trough amplitudes from 4 animals after sleep deprivation. During the LQS state, the hemodynamic response peak and trough amplitudes did not significantly differ across sleep deprivation duration. However, the DQS peak amplitude was significantly smaller after 6 hours deprivation compared to those obtained after 2 hours deprivation (p < 0.1). The trough amplitude did not significantly differ across sleep deprivation periods. In the control condition, the peak and trough amplitudes did not significantly differ ().
Figure 6 Two example inverted evoked optical response traces during the first hour recovery period across light quiet sleep (LQS, A,B) and deep quiet sleep (DQS, C,D) from 2 animals shows progressively smaller responses after sleep deprivation, particularly in (more ...)
Figure 7 The peak and trough mean amplitude and standard error of the vascular response was measured from 4 animals during light quiet sleep (LQS) and deep quiet sleep (DQS) for the first hour recovery period following 2, 4, or 6 hours sleep deprivation (A). There (more ...)