Theta Burst Stimulation Effects on the Right Ventrolateral Prefrontal Cortex and Emotion Regulation

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Abstract Submission 

Joseph Kim¹, Vincent Koppelmans², Brian Mickey², Somi Lee³

¹Brigham and Women's Hospital / Harvard Medical School, Boston, MA, ²University of Utah, Salt Lake City, UT, ³UNIVERSITY OF UTAH, SALT LAKE CITY, UT

Joseph Kim, PhD  
Brigham and Women's Hospital / Harvard Medical School
Boston, MA

Vincent Koppelmans, PhD  
University of Utah
Salt Lake City, UT

Brian Mickey, MD, PhD  
University of Utah
Salt Lake City, UT

Somi Lee, BS  
UNIVERSITY OF UTAH
SALT LAKE CITY, UT

The study aims to understand the impact of neuromodulation, particularly repetitive transcranial magnetic stimulation (rTMS), on the ventrolateral prefrontal cortex (vlPFC) and its role in emotion regulation, especially in older adults. Dysregulated emotions, prevalent in various neuropsychiatric and neurological disorders, are exacerbated by aging-related brain changes. While functional neuroimaging links vlPFC activity to emotion regulation in younger adults, the causal role and the effects of aging on this process remain unclear. The research characterizes the behavioral effects of non-invasive transcranial stimulation to the right vlPFC in emotion regulation, comparing healthy older and younger adults. The study also investigates the impact of this intervention on intrinsic connectivity within emotion regulation-relevant functional networks using resting functional MRI. The current report focuses on key behavioral data analysis results related to the first aim of the study.

Participants included 23 healthy individuals (11 older adults, 12 younger adults) recruited from the Greater Salt Lake area and the University of Utah. Exclusion criteria covered neurological disorders, epilepsy in 1st-degree relatives, intellectual/developmental disability, visual/sensory deficits, estimated IQ < 90, history of major psychiatric disorders, current psychotropic medications, contraindications to rTMS, contraindications to MRI, and pregnancy.

rTMS parameters targeted the vlPFC based on its consistent involvement in emotion regulation. Coordinates were derived from Wager and colleagues' fMRI study, focusing on the right vlPFC [MNI coordinates: x = 52; y = 31; z = -9]. Subjects received 600 pulses of cTBS, iTBS, or Sham stimulation before the emotion regulation task, each in three separate sessions, using a MagVentureTM TMS Cool-B65 Butterfly Coil at 80% of the resting motor threshold.

For the Emotion Regulation Task post-TMS, subjects attended to pictures ("LOOK" condition) or engaged in reappraisal ("DECREASE" condition). Instruction cues ("Neutral Look," "Negative Look," or "Negative Decrease") preceded each picture. Subjects underwent three stimulation sessions, viewing a total of 108 pictures (72 negative, 36 neutral). In the "Look" condition, they attended to the picture without altering feelings; in the "Decrease" condition, they reinterpreted the picture to reduce negative response. After each trial, a visual analog rating scale recorded affect intensity ratings, a key measure of negative affect intensity.

The investigation into Transcranial Magnetic Stimulation (TMS) and emotion regulation yielded key findings. No significant reappraisal differences were found across TMS conditions (cTBS, iTBS, sham), suggesting TMS lacked a distinct impact, potentially influenced by baseline variability. Demographic factors (age, income, education) did not predict emotion regulation, indicating their limited role in TMS impact. While no significant difference in sham stimulation response was noted between Older Adults (OA) and Younger Adults (YA), a contrast emerged with iTBS. YA showed a greater increase in reappraisal effectiveness, aligning with TMS studies favoring younger individuals. Within YA, increasing age correlated positively with baseline reappraisal effectiveness, possibly linked to frontal lobe development. Surprisingly, in OA, older age was positively associated with a greater cTBS-induced emotion regulation increase, aligning with TMS studies reporting unexpected inhibitory effects with age. These nuanced findings illuminate the intricate interplay between TMS, age, and emotion regulation.

Age-related contrast emerged within iTBS. YAs displayed greater increase in reappraisal effectiveness compared to OAs. Notably, in OA, older age was unexpectedly parametrically associated with a greater cTBS-induced emotion regulation effectiveness increase, which warrants further investigation in future studies.

Non-invasive Magnetic/TMS ¹

Psychiatric (eg. Depression, Anxiety, Schizophrenia)

Emotion and Motivation Other ²

Executive Function, Cognitive Control and Decision Making

Aging

ADULTS

Emotions

Transcranial Magnetic Stimulation (TMS)