Relationships Between Sleep Spindles and Activities of the Cerebral Cortex After Hemispheric Stroke As Determined by Simultaneous EEG and MEG Recordings

Abstract

This study aimed to determine the relationships between the amplitude and cortical-activating areas in each hemisphere for 14-Hz centro-parietal spindles to clarify the involvement of the cortex in the asymmetry of spindles after hemispheric stroke with putaminal or thalamic hemorrhage using simultaneous recording of the electroencephalogram and magnetoencephalogram. Spontaneous cortical activities during sleep stage 2 (spindles) were simultaneously recorded from 10 patients with putaminal or thalamic hemorrhage with a 60-channel electroencephalogram and a 306-channel whole-head magnetoencephalogram. Based on the frequencies and cortical distributions recorded with electroencephalogram, the 14-Hz centro-parietal and 12-Hz frontal spindles were differentiated. The cortical sources of the 14-Hz centro-parietal spindles were identified with magnetoencephalogram as equivalent current dipoles. Activation centered in four areas, the pre- and postcentral areas in posterior frontal cortex and parietal cortex of each hemisphere. However, these areas were not always activated simultaneously. Reduction of amplitude in the affected hemisphere after hemispheric stroke indicated reduction of areas of activation or activation strengths in the ipsilateral hemisphere. For some spindles, when reduction of amplitude of above 50% occurred in the affected hemisphere compared with the nonaffected hemisphere, no activation occurred in the ipsilateral hemisphere. Reduction of amplitude was related to the reduction of areas of cortical activation and activation strengths. Reduction of amplitude also occurred over the nonaffected hemisphere, and reduction of cortical activating area and activation occurred in the nonaffected hemisphere, suggesting that the cerebral hemispheres are involved in the eneration of spontaneous sleep spindles. The stronger ipsilateral effects of cerebral lesions on spindle oscillations indicated reduction of amplitude of sleep spindles in the ipsilateral hemisphere, as well as reduction of cortical activation of spindle oscillations and underlying corticothalamic projections. Simultaneous electroencephalogram and magnetoencephalogram recordings can yield valuable findings concerning the functional asymmetry between hemispheres after hemispheric stroke from the relationships between the amplitude and patterns of cortical activation associated with spindles.

Nocturnal Deterioration after Ischemic Stroke and Autonomic Dysfunction: Hypothesis and Implications

“…Gottselig et al [31] (2002) found an association between the power and coherence of sleep spindle frequency activity and long-term stroke outcome. Urakami [32] (2009) showed that reduced spindles were associated with an absence of activation in the ipsilateral hemisphere.…”

Magnetoencephalography in Stroke Recovery and Rehabilitation

“…Sleep, through neuroplastic and encoding processing mediated mainly by slow waves sleep (SWS) and sleep spindles, plays an active role in this recovery process. Indeed, the finding that sleep spindles of stroke patients have a reduced amplitude as well as a reduced cortical activation than healthy subjects ( 73 , 74 ) and that SWS remains lower over the perilesional area ( 75 ) supports the fundamental role of sleep in recovery.…”

Automated detection of sleep spindles in the scalp EEG and estimation of their intracranial current sources: comments on techniques and on related experimental and clinical studies

“…Application of inversion techniques in patient populations should be encouraged, as in investigating the cortex involvement in the asymmetry of spindles after hemispheric stroke (Urakami, 2009 ) and the generation of spindles in temporal lobe epilepsy (Del Felice et al, 2013 ). A topic that has not yet been addressed concerns the extraction of parameters related to the phenomenology of intracranial current sources.…”