AUTHOR=Muhammad Naeem , Sonkusare Saurabh , Ding Qiong , Wang Linbin , Mandali Alekhya , Zhao Yi Jie , Sun Bomin , Li Dianyou , Voon Valerie 

TITLE=Time-locked acute alpha-frequency stimulation of subthalamic nuclei during the evaluation of emotional stimuli and its effect on power modulation

JOURNAL=Frontiers in Human Neuroscience

VOLUME=Volume 17 - 2023

YEAR=2023

URL=https://www.frontiersin.org/journals/human-neuroscience/articles/10.3389/fnhum.2023.1181635

DOI=10.3389/fnhum.2023.1181635

ISSN=1662-5161

ABSTRACT=Introduction: Deep brain stimulation (DBS) studies in Parkinson’s Disease (PD) targeting subthalamic nucleus (STN) have characterized its spectral properties across cognitive processes. In emotional evaluation tasks, specific alpha frequency (8-12 Hz) event related de-synchronization (ERD) (reduced power) has been demonstrated. Time locked stimulation of STN relative to stimuli onset have shown subjective positive valence shifts with 10 Hz but not with 130 Hz. However, neurophysiological effects of stimulation itself on power modulation have not been investigated. We aim to investigate effects of acute stimulation of right STN on concurrent power modulation in the contralateral STN and frontal scalp EEG. From our previous work, we had a strong a priori hypothesis that negative imagery without stimulation would be associated with alpha ERD; negative imagery with 130 Hz stimulation also associated with alpha ERD given the lack of its effect on subjective valence ratings; negative imagery with 10 Hz stimulation to be associated with enhanced alpha power given the shift in behavioural valence ratings.
Methods: Twenty-four subjects with STN DBS underwent emotional picture viewing tasks comprising neutral and negative pictures. In a subset of these subjects, the negative images were associated with time-locked acute stimulation at either 10 Hz or 130 Hz. Power of signals were estimated relative to the baseline and subjected to non-parametric statistical testing. 
Results: As hypothesized, in 130 Hz stimulation condition, we show a decrease in alpha power to negative versus neutral images irrespective of stimulation. In contrast, this alpha power decrease was no longer evident in the negative 10 Hz stimulation condition consistent with a predicted increase in alpha power. Greater beta power in the 10 Hz stimulation condition along with correlations between beta power across the 10 Hz stimulation and unstimulated conditions suggest physiological and cognitive generalization effects. 
Conclusions: Acute alpha specific frequency stimulation presumably was associated with a loss of this expected decrease or desynchronization in alpha power to negative images suggesting the capacity to facilitate the synchronization of alpha and enhance power. Acute time locked stimulation has the potential to provide causal insights about the spectral frequencies and temporal dynamics of emotional processing.