EFFECTS OF HEMI-THALAMIC DAMAGE ON K-COMPLEXES EVOKED BY MONAURAL STIMULI DURING MIDAFTERNOON SLEEP

Polygraphic recordings of midafternoon sleep were made in two patients with unilateral hemorrhagic infarction in the thalamus. One patient h ad massive signs of reduced attention in the contralesional space foll owing 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) el icited 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 It-complexes in the right cerebral hemisp here, whereas normal it-complexes continued to appear at C3 as well as at Fz. In neither patient did the frequency of evoked It-complexes de pend on the side of the stimulated ear. Unlike It-complexes, sleep spi ndles were bilaterally absent in patient 1. The right hemisphere does not seem to have a special role in control of circuits generating K-co mplexes.