Effects of hemi-thalamic damage on K-complexes evoked by monaural stimuli during midafternoon sleep.

Polygraphic recording of midafternoon sleep were made in two patients with unilateral hemorrhagic infarction in the thalamus. One patient had massive signs of reduced attention in the contralesional space following right lateral thalamic lesion. The other patient had infarction centered in the left posterior ventrolateral thalamus with no signs of hemineglect. In both cases, waking and sleep records showed symmetric background EEG at C3 and C4. In contrast, monaural sounds (clicks) elicited bilaterally symmetrical K-complexes only in the second patient. In the other patient with right thalamic lesion, both left- and right-ear clicks failed to elicit K-complexes in the right cerebral hemisphere, whereas normal K-complexes continued to appear at C3 as well as at Fz. In neither patient did the frequency of evoked K-complexes depend on the side of the stimulated ear. Unlike K-complexes, sleep spindles were bilaterally absent in patient 1. The right hemisphere does not seem to have a special role in control of circuits generating K-complexes.