Table 2.
Sleep spindle activity and cognitive functions (N = 8).
| Study | Cognitive assessment (purpose) | Spindle density | Spindle duration | Spindle amplitude | Peak frequency | Integrated spindle activity | Spindle number | Sigma power |
|---|---|---|---|---|---|---|---|---|
| Baandrup et al. [35] | Brief assessment of cognition in schizophrenia (Verbal memory; working memory; motor speed; verbal fluency; attention and processing speed; executive function) | Only motor speed was positively associated with slow sleep spindle density (Beta = 0.70, SE = 0.25, p = 0.008) | No association | No association | No association | NR | NR | NR |
| Goder et al. [36] | International affective picture system -Learning of pictures before sleep and recognizing ‘new/old’ pictures on the next day (Visual memory) |
Sleep spindle density was positively correlated with recognition accuracy for neutral pictures in both patients (r = 0.48, p < 0.05) and healthy controls (r = 0.64, p < 0.01), but no association for emotional pictures. | NR | NR | NR | NR | NR | NR |
| Manoach et al. [11] | Wisconsin card sort test (Executive function) Trail making tests A and B (Cognitive processing speed, attention, executive function) Block design test (Spatial visualization ability and motor skill) Immediate recall of the California verbal learning test (Verbal memory) Ammons quick test (Verbal IQ) Wide range achievement test-revised, reading portion (Premorbid IQ) |
Spindle density was positively associated with better performance on Trails A and B, Wisconsin card sort test, Wide range achievement test-revised, reading portion, and Ammons quick test -All groups (schizophrenia, non-psychotic first-degree relatives and healthy controls) showed similar patterns of association |
No association | Spindle amplitude was positively associated with better Trail making test B performance, less WCST perseverative errors, and better Block design test performance (Not different by groups) | No association | NR | NR | No association |
| Wamsley et al. [40] | Finger tapping motor sequence task (Procedural memory) | Overnight improvement in tapping motor sequence task was positively associated with spindle density (r = 0.45, p = 0.04) No correlation for controls |
No association | No association | No association | NR | Overnight improvement in tapping motor sequence task was positively associated with spindle number (r = 0.46, p = 0.04) | No association |
| Ramakrishnan et al. [41] | Multiple Choice Word Test-B (Premorbid IQ) Digit symbol test (Motor speed, executive function, attention, visuoperceptual function) Controlled oral word association test (Verbal fluency) Tower of London (Executive function) Mirror tracing (Procedural memory) |
NR | NR | NR | NR | No relationship between performance and integrated spindle activity. Relationship with IQ not examined. |
NR | NR |
| Keshavan et al. [34] | Ammons quick test (Verbal IQ) Trail making test B (Cognitive processing speed, attention, executive function) Wisconsin card sort test (Executive function) |
NR | NR | NR | NR | NR | NR | Spindle power positively correlated with performance on Trail making test B (time and errors) and Wisconsin card sort test (perseverative errors), but not with verbal IQ. |
| Ferrarelli et al. [10] | Ravens progressive matrices test (Non-verbal IQ) | NR | NR | NR | NR | Ravens progressive matrices test was not associated with integrated spindle activity or spindle number Not reported for controls |
NR | |
| Forest et al. [42] | Selective attention task Sustained attention task (Attention) |
1. Higher sleep spindle density was associated with lower median reaction times in selective attention task in both patients (r = −0.75, p < 0.05) and controls (r = −0.71, p < 0.05). 2. No correlation for sustained attention task in both patients and controls. |
NR | NR | NR | NR | NR | NR |
| Sleep spindle activity and positive/negative symptoms (N = 8). | |||||||
|---|---|---|---|---|---|---|---|
| Study | Spindle density | Spindle duration | Spindle amplitude | Frequency | Integrated spindle activity | Spindle number | Sigma power |
| Kaskie et al. [38] | Negative correlation between negative symptoms and spindle duration (r = −0.60, p = 0.006), and spindle density (r = −0.50, p = 0.025). | No association | NR | NR | NR | NR | |
| Schilling et al. [39] | No association | No association | No association | No association | NR | NR | NR |
| Goder et al. [36] | No association | NR | NR | NR | NR | NR | NR |
| Manoach et al. [11] | No association | No association | Positive correlation between spindle amplitude and positive symptoms (No correlation coefficient reported; R2 = 0.26, p = 0.05). | No association | NR | NR | NR |
| Wamsley et al. [40] | No association | No association | Negative correlation between positive symptoms and spindle amplitude (r = −0.47, p = 0.03) | No association | NR | NR | Negative correlation between positive symptoms and sigma power (r = −0.45, p = 0.04). |
| Keshavan et al. [34] | NR | NR | NR | NR | NR | NR | No association |
| Ferrarelli et al. [10] | NR | NR | NR | NR | 1. Negative correlation between spindle number and stereotyped thinking of PANSS negative symptoms (r = −0.32, p = 0.028). 2. Negative correlation between ISA and spindle number with positive symptoms of PANSS (ISA: −0.40, p = 0.005; spindle number: r = −0.37, p = 0.01). 3. Spindle number was correlated only with conceptual disorganization (r = −0.34, p = 0.03) and hallucinations (r = −0.40, p = 0.01). 4. ISA was correlated exclusively with hallucinations (r = −0.48, p = 0.002). |
NR | |
| Ferrarelli et al. [9] | NR | NR | NR | NR | No association | NR | NR |
Abbreviation: ISA, Integrated spindle activity; NR, not reported; NREM, non-rapid eye movement; PANSS, Positive and Negative Syndrome Scale.