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1Institute of Behavioural Sciences, Semmelweis University, Budapest, Hungary
2Medical and Pharmaceutical University of Targu-Mures, Romania
3Department of Psychology, Károli Gáspár University, Budapest, Hungary
4Department of Neurology, National Institute of Psychiatry and Neurology, Budapest, Hungary
Aims: The cerebral cortex is a major modulator of sleep electroencephalogram (EEG) oscillations, and the latter were shown to reflect corticothalamic resonance as well as synaptic plasticity and neural transmission efficacy phenomena. There is evidence for a sleep-EEG alteration in various forms of dementia as well as for a correlation between certain sleep-EEG features and cognitive performances in normal non-demented subjects. Our aim was to detect sleep-EEG based biomarkers of low visuospatial ability in normal non-demented subjects. We hypothesized that individual differences in the sleepslow oscillation as well as in slow- and fast sleep spindle activity reflect visuospatial memory ability in a regionand frequency-specific manner.
Methods: Nineteen subjects slept two consecutive nights in the sleep laboratory (EEG: 10–20 system, polygraphy: submental EMG, left- and right EOG, ECG). The immediate (3 minutes) and delayed (30 minutes) recall as well as the recognition trial of the Rey-Osterrieth Complex Figure Test was used for assessing individual differences in visuospatial memory ability. An individual adjustment of frequency and amplitude criteria of slow- and fast sleep spindling was used in sleep spindle analysis and detection.
Results: Here we report negative correlations of visuospatial recall performance with integrated relative amplitude spectra of slow spindle frequency activity. Moreover, positive correlations between visuospatial recall performance and right parietal fast spindle density as well as visuospatial recognition performance and the integrated amplitude spectra of fast spindle frequency activity in the right centroparietal area were observed. Neither the sleepslow oscillation, nor the grouping of slow or fast sleep spindles by the slow oscillation correlated significantly with visuospatial abilities.
Conclusions: Results suggest that slow spindle frequency activity is a global, region-independent, negative biomarker of visuospatial memory ability, while region-specific differences in fast sleep spindle activity and density are correlates of the neuropsychological performances associated with the respective regions. Stable individual differences in functional neuroanatomy and cortical connectivity may shape both sleep-EEG oscillations and visuospatial memory ability.
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