Abstract
Sleep spindles are major oscillatory components of Non-Rapid Eye
Movement (NREM) sleep, reflecting hyperpolarization-rebound sequences of
thalamocortical neurons. Reports suggest a link between sleep spindles
and several forms of high frequency oscillations which are considered as
expressions of pathological off-line neural plasticity in the central
nervous system. Here we investigated the relationship between thalamic
sleep spindles and ripples in the anterior and mediodorsal nuclei (ANT
and MD) of epilepsy patients. Whole-night LFP from the ANT and MD were
co-registered with scalp EEG/polysomnography by using externalized leads
in 15 epilepsy patients undergoing a Deep Brain Stimulation protocol.
Slow (~12 Hz) and fast (~14 Hz) sleep
spindles were present in the human ANT and MD and roughly, 20 %
of them were associated with ripples. Ripple-associated thalamic sleep
spindles were characterized by longer duration and exceeded pure
spindles in terms of 100–200 Hz thalamic, but not cortical activity as
indicated by time-frequency analysis. Furthermore, ripple amplitude was
modulated by the phase of sleep spindles within both thalamic nuclei. No
signs of pathological processes were correlated with measures of ripple
and spindle association, furthermore, the density of ripple-associated
sleep spindles in the ANT and MD showed a positive correlation with
general intelligence. Our findings indicate the complex and multifaceted
role of the human thalamus in sleep spindle-related