Slowing of M1 oscillations in brain tumor patients in resting state and during movement

Electroencephalography characteristics of patients with supratentorial glioma in different consciousness states induced by propofol

Gliomas are the most common primary intracranial malignant tumors. Some of these patients exhibit previously clinically undetected neurological deficits after sedation. The absence of neurophysiological evidence for this phenomenon limits the use of time-sensitive monitoring methods. The study aims to compare differences between glioma patients under sedation and those without intracranial lesions by comparing their EEG features. Twenty-one patients without intracranial tumors and 21 with frontal lobe supratentorial gliomas were enrolled. The EEG power spectrum of the glioma group was comparable to that of the control group for both sides of the brain (P>0.05 for all frequencies). Compared with those without intracranial lesions, the weighted phase lag index (wPLI) in the alpha and beta bands on the non-occupied side decreased. Glioma patients had weaker functional connectivity during sedation than patients without intracranial lesions, manifesting as reduced functional connectivity on the non-occupied side.

Atypical somatosensory-motor cortical response during vowel vocalization in spasmodic dysphonia

OBJECTIVE

Spasmodic dysphonia (SD) is a debilitating voice/speech disorder without an effective cure. To obtain a better understanding of the underlying cortical neural mechanism of the disease we analyzed electroencephalographic (EEG) signals of people with SD during voice production.

METHOD

Ten SD individuals and 10 healthy volunteers produced 50 vowel vocalization epochs of 2500 ms duration. Two EEG features were derived: (1) event-related change in spectral power during vocalization relative to rest, (2) inter-regional spectral coherence.

RESULTS

During early vocalization (500-1000 ms) the SD group showed significantly larger alpha band spectral power over the left motor cortex. During late vocalization (1000-2500 ms) SD patients showed a significantly larger gamma band coherence between left somatosensory and premotor cortical areas.

CONCLUSIONS

Two atypical patterns of cortical activity characterize the pathophysiology of spasmodic dysphonia during voice production: (1) a reduced movement-related desynchronization of motor cortical networks, (2) an excessively large synchronization between left somatosensory and premotor cortical areas.

SIGNIFICANCE

The pathophysiology of SD is characterized by an abnormally high synchronous activity within and across cortical neural networks involved in voice production that is mainly lateralized in the left hemisphere.

Cross-modal repetition effects in the mu rhythm indicate tactile mirroring during action observation

Similar cortical activations during the experience and observation of touch suggest the presence of a tactile mirroring system. However, the specificity of observation-related activity - i.e., whether observation excites the same representations as experience of that specific tactile stimulation - is still to be established. Furthermore, central mu rhythms are attenuated during the experience and observation of touch, and also during action observation and execution, making it unclear whether they index processing of predominantly tactile or motor features of observed actions. The present study used an electroencephalography (EEG) cross-modal repetition paradigm to assess the relative tactile and motor specificity of mu attenuation during action observation. Two experiments were carried out during which participants executed and observed actions in alternation, and the repetition of either tactile or motor features of the actions were manipulated. The mu signal over central electrodes varied as a function of tactile repetition, consistent with the claim of a tactile mirroring system and its reflection in the mu signal. Of note was the fact that mu attenuation was sensitive only to manipulation of tactile - not motor - properties of actions, suggesting that caution should be employed when interpreting mu effects during action observation as reflective of motor mirroring.