Transcranial Ultrasound (TUS) applied to Corpus Callous Diminishes EEG Alpha Power

97 

Abstract Submission 

PK Douglas¹, Pardis Azarmi-por², Joshua Cain³

¹IACS, Los Angeles, CA, ²UCLA, Los Angeles, CA, ³Institute for Advanced Consciousness Studies, Los Angeles, CA

PK Douglas  
IACS
Los Angeles, CA

Pardis Azarmi-por  
UCLA
Los Angeles, CA

Joshua Cain  
Institute for Advanced Consciousness Studies
Los Angeles, CA

The alpha rhythm is perhaps the most prominent feature in EEG recordings, yet its spatial origins and functional significance have been debated since its was first observed in 1929. In Berger's pioneering work, he noted prominent "alpha waves" that were abolished with the eyes open in the first recorded human EEG (Berger 1929). Combined cortical surface, intracortical depth electrode, and intra-thalamic recordings provided additional evidence that alpha may be generated by the pulvinar nucleus and other nuclei of the thalamus influence cortical alpha activity (Lopes da Silva 2023). At birth and throughout infancy, there is no distinguishable EEG alpha rhythm (Trujillo, Gao et al. 2019). Given that the emergence of the alpha rhythm appears to parallel the development of myelin and the formation of white matter fiber bundles, we hypothesized that white matter signaling may also play a role in generating or carrying the alpha rhythm. To explore this theory, we applied transcranial ultrasound (TUS) sonication to healthy adult subjects in the following brain regions: corpus callosum, medial dorsal thalamus, and the pulvinar nucleus and measured changes in EEG alpha power.

All study protocols were approved by the CCN IRB prior to commencing studies. A total of 24 subjects were enrolled in the study. A subset of subjects (N=8) returned on a different day to receive sonication at a different brain target. Thus, there were a total of 30 data collection sessions across the study cohort (mean age = 19 +/- 6 y.o., 33% female). EEG data was collected at baseline, following a sham condition, and after TUS sonication. EEG was recorded while subjects performed an "eyes open/eyes closed" task consisting of 3 blocks of each task for 30 seconds each to permit time for changes in alpha power. T1 MRI scans were used for neuronavigation purposes. Subjects received sonication to one of the three brain targets or 30 seconds on, and 30 seconds off for a total of 10 minute.

During both baseline and "sham-TUS" EEG recordings, we observed a prominent alpha peak in spectral decompositions across participants during the eyes closed. We found no significant alpha power changes following TUS to thalamus or pulvinar (Figure 1). In contrast, we observed a significant diminution in alpha power following sonication of the corpus callosum (Figure 2).

TUS applied to the medial dorsal thalamus and pulvinar nuclei, did not significantly alter alpha power during the eyes closed state, when the alpha peak is conspicuous. The frequency position of the alpha peak also remained unchanged when TUS was applied to gray matter targets. In contrast, TUS applied to corpus callosum caused a prominent desynchronization in alpha power during the idle eyes closed state, as evident across both frequency and time-frequency decompositions. Our results provide exciting new evidence that the corpus callosum is either responsible for, or is an integral component requisite for the generation of the alpha rhythm in human EEG recordings.

Sonic/Ultrasound ¹

EEG/MEG Modeling and Analysis ²

Electroencephaolography (EEG)

Modeling

Thalamus

ULTRASOUND