Induced emotional state modulates aperiodic activity of the amygdala
Poster No:
734
Submission Type:
Abstract Submission
Authors:
Haeorum Park1, Carl Hacker1, Hohyun Cho1, Eric Leuthardt1, Peter Brunner1, Jon Willie1
Institutions:
1Washington University School of Medicine in St. Louis, St. Louis, MO
First Author:
Co-Author(s):
Introduction:
Mood disorders, leading to diminished motivation and, in extreme cases, suicidal behavior, saw a dramatic increase of over 25% during the COVID-19 pandemic. While the underlying mechanisms have been extensively explored through neuroimaging techniques such as EEG, MRI, and MRS, electrophysiological biomarkers of mood, directly recorded from cortical and subcortical regions, remain largely unexplored. Recent studies suggest that the 1/f slope in the frontal lobe's power spectrum is a significant indicator of depression severity. However, the role of aperiodic exponents representing the 1/f slope, particularly in the amygdala, a crucial center for emotional processing, is not well understood. This study aims to shed light on the amygdala's electrophysiological responses in emotionally induced states, potentially contributing to a deeper understanding of mood disorder pathophysiology.
Methods:
In this study, we elicited emotional responses to 20-40-second long videos while simultaneously recording local field potentials in 16 patients with intractable epilepsy who underwent intracranial monitoring prior to resective brain surgery. These videos were previously evaluated by Samide et al. (2020), and rated for emotional valence and arousal by 100 healthy subjects. After viewing each video, we asked our intracranially monitored subjects how watching this video made them feel. Subjects responded on a Likert scale ranging from one (unpleasant) to nine (pleasant). In our post-hoc analysis, for each subject, we determined the correlation between the aperiodic exponents of the power spectrum (i.e., the 1/f slope) and normative valence/arousal (from 100 health subjects), as well as subject-specific Likert scale ratings (from our 16 subjects). To determine the aperiodic component, we applied the FOOOF algorithm to the neural signals within the canonical beta and gamma bands (i.e., 12-50 Hz frequency range). To account for the inherently negative nature of the 1/f slope, we used the absolute value of this slope for a more intuitive representation of steeper exponents. We conducted a region-wise statistical analysis to compare the aperiodic slopes between high (1st quantile) and low (4th quantile) mood states. Subjects without amygdala electrode contact were excluded from our analysis.
·Fig 1. Example of video stimulus.
Results:
We found a significant positive correlation between the 1/f slope and normative valence of the videos (r=0.619, p<0.001) and a significant negative correlation between the 1/f slope and normative arousal (r=-0.448, p<0.001). The subjects rated the videos on a sigmoid-shaped psychometric curve, confirming the tendency to perceive positively valenced stimuli as pleasant and negatively valenced stimuli as unpleasant (refer to Fig 2). Within the amygdala, the majority of electrodes (60%) showed a statistically significant negative correlation between the aperiodic exponent and mood ratings, indicating that a flattened 1/f slope in the power spectrum was associated with positive emotions. This negative correlation was statistically significant in both one-sample and paired-sample hypothesis testing (p=0.003), with less than 20% of electrodes exhibiting a statistically significant positive correlation.
Conclusions:
Prior research indicates that low and high-power activity in the prefrontal cortex is inversely correlated with depression severity, suggesting that the aperiodic exponent may vary with mood states. Building on this, our study explores emotional states induced by video stimuli, proposing a link between power and aperiodic slope that represents emotional fluctuations. We observed that positive emotional states induce flatter power spectra within the amygdala, underscoring its critical role as an emotional hub. Our observation aligns with the canonical understanding of the aperiodic exponent of the power spectrum, highlighting the significance of the amygdala's aperiodic electrophysiological activity in emotional processing.
Disorders of the Nervous System:
Psychiatric (eg. Depression, Anxiety, Schizophrenia) 2
Emotion, Motivation and Social Neuroscience:
Emotional Perception 1
Emotion and Motivation Other
Keywords:
ELECTROCORTICOGRAPHY
Electroencephaolography (EEG)
Emotions
1|2Indicates the priority used for review
·Fig 2. Boxplot of emotional states and valence. Amygdala electrodes placements.
Provide references using author date format
Xiao, J. (2023). 'Decoding depression severity from intracranial neural activity'. Biological Psychiatry.