Discussion
We investigated the occurrence of sleep spindles and ripples in the
human anterior and mediodorsal thalamus and those associations with
epilepsy characteristics and general intelligence. Sleep
spindles were detected both in the ANT and MD. The occurrence of sleep
spindles in the human ANT were confirmed in previous studies (Tsai et
al. 2010). We demonstrated that spindles are also present in the human
MD. The duration of slow and fast spindles was similar in the two
thalamic nuclei, however the overall density of fast sleep spindles was
lower in the MD compared to the ANT. In the majority of cases where
thalamic-scalp sleep spindle co-occurrences were detected, ANT and MD
sleep spindles slightly lagged behind cortical ones, which coheres with
available reports (Tsai et al. 2010) and suggests the prevailing role of
corticofugal fibers in the herein studied phenomena. In a recent study,
Bastuji et al. (2020) recorded sleep spindles from different parts of
the posterior thalamus. These results indicate that anterior,
mediodorsal and posterior thalamic nuclei are involved in the proper
functioning of the NREM sleep-related thalamo-cortical network
generating mid-frequency oscillations in the burst-firing mode.