Table 4.
Sleep Studies.
| Study | Cognitive Domains | EEG Indices | Sample Size | Correlations between EEG Indices and Cognitive Functions in Patients and High-Risk Subjects |
|---|---|---|---|---|
| Baandrup et al., 2019 [260] | Verbal memory, Working memory, Verbal fluency, Attention, Processing speed and Executive functions (BACS) |
Sleep spindles
characteristics |
SCZ = 37 (ICD-10) Mean age: 47 y |
No significant correlation between sleep spindle characteristics and cognitive domains |
| Bartsch et al., 2019 [261] | Memory consolidation (MST) |
Slow waves density amplitude and
duration and sleep spindles coordination |
SCZ = 21 HCs = 19 (SCID-DSM-IV) Mean age: SCZ = 34; HCs = 36) |
SCZ = HCs (for slow wave density, amplitude and duration); SCZ < HCs (coupling of slow waves and sleep spindles) No correlation between amplitude, density and duration of slow waves or sleep spindles features and memory consolidation |
| Forest et al., 2007 [262] | Attention (attention task) |
Sleep spindle
density and sleep stages duration |
SCZ = 8 HCs = 8 (SCID-DSM-IV) Mean age: SCZ = 31 y; HCs = 21 y |
SCZ = HCs Positive correlation between sleep spindles density and percentage of time spent in stage 4 of sleep and attention |
| Gerstenberg et al., 2020 [263] | Verbal Learning (AVLT); Executive functioning (TMT) |
Sleep spindle
density |
EO-SCZ = 12 HCs = 24 (DSM-IV; SCID) Mean age: EO-SCZ = 17 y; HCs = 17 y |
SCZ < HCs No significant correlation between sleep spindle density and verbal learning or executive functioning |
| Göder et al., 2015 [264] | Memory/Recognition (Memory task) |
Sleep spindle
density |
SCZ = 16 HCs = 16 (ICD-10) Mean age: SCZ = 29 y; HCs = 28 y |
SCZ < HCs Positive correlation between sleep spindle density and memory performance |
| Keshavan et al., 2004 [265] | Memory (WMS); Executive functions (WCST) | Non-linearity EEG scores during sleep | SCZ = 10 HCs = 10 (SCID-DSM-IV) Mean age: SCZ = 20 y; HCs = 20 y |
SCZ < HCs Positive correlation between non-linear EEG complexity and memory and executive functions |
| Manoach et al., 2014 [266] | Executive functions (WCST and TMT); Verbal learning (CVLT) | Sleep spindle amplitude and density | SCZ = 17 HCs = 25 (DSM-IV; SCID) Mean age: SCZ = 28 y; HCs = 27 y |
SCZ < HCs Positive correlation between sleep spindle density and amplitude and executive functions |
| Ramakrishnan et al., 2012 [267] | Problem solving (ToL, Digit Symbol Test); Executive functioning (TMT) | K-complexes during sleep | SCZ = 20 (DSM-IV; SCID) Mean age: 41 y |
Positive correlation between the number of K-complexes and executive functioning and problem solving |
| Wamsley et al., 2012 [268] | Motor memory (motor memory task) |
Sleep spindle
number and density |
SCZ = 21 HCs = 17 (DSM-IV; SCID) Mean age: SCZ = 36 y; HCs = 34 y |
SCZ < HCs Positive correlation between sleep spindle density and memory performance |
The column “EEG Indices” reports the EEG index considered in that study, while in the last column, differences between patients and controls, as well as correlations with cognition for that measure are reported. Auditory Verbal Learning Test (AVLT); the California Verbal Learning Test (CVLT); Controlled Oral Word Association Test (COWAT); subjects with early onset schizophrenia (EO-SCZ); Healthy controls (HCs); International Statistical Classification of Diseases and Related Health Probles (ICD); motor-sequencing task (MST); subjects with schizophrenia (SCZ); Tower of London (ToL); Wisconsin Card Sorting Test (WCST); Wechsler Memory Scale (WMS); Trail-Making Test (TMT).