Table 7.
Comparison of previous studies using acoustic stimulation to boost slow oscillations and spindle and their effects on memory
| Study | Study design | Behavioral results | EEG results | |
|---|---|---|---|---|
| Ngo et al., 2013 | N = 11 healthy young adults (mean ± SD age, 24.2 ± 2.98 years) | Stimulation protocol | Hedges gav = 1.07 Retention (presleep − postsleep): Stim: 22.2 ± 2.3 words Sham: 13.0 ± 2.5 words |
Increase in slow-wave and spindle power |
| Closed-loop Two-pulse stimulation overnight sleep (7 h) | ||||
| Memory tests | ||||
| 120 semantically related word pairs | ||||
| Cox et al., 2014b | N = 12 healthy adults (age range, 18–23 years; 11 females) | Stimulation protocol | No behavioral effect observed | Increased slow-wave amplitude and spindle band power with sounds targeted at up-state |
| Closed-loop One-pulse stimulation Evening nap (2 h) | ||||
| Memory tests | ||||
| Sound stimulus memory task | ||||
| Ong et al., 2016 | N = 16 healthy young adults (mean ± SD age, 22 ± 1.4 years) | Stimulation protocol | Hedges gav = 0.41Retention (presleep − postsleep):Sham: −1.72 ± 4.16 SDsStim: 0.0 ± 3.76 SDs | Increased slow-wave amplitude, theta, and fast-spindle activity |
| Closed-loopFive consecutive pulsesAfternoon nap (1.5 h) | ||||
| Memory tests | ||||
| 40 semantically related word pairs | ||||
| Weigenand et al., 2016 | N = 26 healthy young adults (mean age, 22.2 years; age range, 18– 28 years) | Stimulation protocol | No behavioral effect observed | Increase in slow-wave and increase in spindle power with first pulse |
| Open-loopThree consecutive pulse stimulationOvernight sleep (7 h) | ||||
| Memory tests | ||||
| 120 semantically related word pairs1 | ||||
| Leminen et al., 2017 | N = 15 healthy adults (mean age, 30.5 years; range, 23–42 years) | Stimulation protocol | Hedges gav = 0.65Retention (presleep – postsleep):Stim: 21.1 ± 7.7 SDsSham: 15.6 ± 8.1 SDsNo behavioral effect on face–name memory, finger tapping, or picture memory (tasks 2–4) | Increase in slow-wave and spindle power |
| Closed-loopSingle-pulse stimulationOvernight sleep (7 h) | ||||
| Memory tests | ||||
| 120 semantically related word pairs2 Face–name association testFinger-tapping testPicture recognition task | ||||
| Papalambros et al., 2017 | N = 13 healthy older adults (mean age, 75.2 years; age range, 60–84 years) | Stimulation protocol | Hedges gav = 0.77Retention (presleep – postsleep):Stim: 9.2 ± 7.93 SDsSham: 3.1 ± 6.85 SDs | Increase in slow-wave and spindle power |
| Closed-loopFive-pulse, phase-locked loop stimulationOvernight sleep (8 h) | ||||
| Memory tests | ||||
| 88 semantically related word pairs | ||||
| Ngo et al., 2019 | N = 24 healthy young adults (mean ± SD age, 23.9 ± 3.42 years) | Stimulation protocol | No behavioral effect observed | Acute increase in slow-wave and spindle power, but no effect on total overnight slow-wave and spindle power |
| Closed-loopSeven-click spindle stimulationOvernight sleep (7 h) | ||||
| Memory tests | ||||
| 120 semantically related word pairs1 | ||||
For each study, the brief description of the subject pool, stimulation and memory protocols, effect size (Hedges gav) of the behavioral effect (if applicable), and overall electrophysiological findings are provided.
1
Same word lists used in Ngo et al., 2013.
2
Translated from list used in Ngo et al., 2013.