TMS direct effects of orbitofrontal cortex stimulation: An interleaved TMS-fMRI study
Poster No:
127
Submission Type:
Abstract Submission
Authors:
Hyuntaek Oh1, Julia Myerson2, Ramiro Salas1
Institutions:
1Baylor College of Medicine, Houston, TX, 2The Menninger Clinic, Houston, TX
First Author:
Co-Author(s):
Introduction:
Transcranial magnetic stimulation (TMS) is an FDA-approved non-invasive brain stimulation technique that effectively treats a variety of psychiatric disorders, including major depressive disorder (MDD). TMS over the left dorsolateral prefrontal cortex (dlPFC) has shown promise as a therapeutic tool for treatment-resistant depression (TRD). Recently, TMS has been applied to the orbitofrontal cortex (OFC) as a new possible treatment tool for substance use disorders (SUD). The OFC has been associated with decision-making and goal-directed behavior, and previous studies have found that functional connectivity dysfunction in the OFC is associated with the abuse of various substances. However, the direct effects of OFC stimulation using TMS, which could be a promising brain target for SUD, are largely unknown. Here, we investigated the mechanisms by which TMS induces functional activation in the human brain network by capturing dynamic changes. Specifically, we combined TMS with functional magnetic resonance imaging (fMRI) in an interleaved TMS-fMRI approach to characterize functional and distributed networks through the causal manipulation of human brain activity.
Methods:
Healthy participants (N = 15) were recruited locally in Houston, Texas. Depression, substance use, and suicidality were assessed using the PHQ-9, WHO-ASSIST, and SBQ-9, respectively. Urine samples were collected before the fMRI scan to confirm eligibility. Subjects reported no history of neurological or psychiatric disorders, and they signed a written informed consent form to be enrolled in this study. The interleaved TMS-fMRI setup utilized the posterior elements of the 12-channel head matrix coil and the flexible 6-channel body matrix coil, creating sufficient space to accommodate a custom-built coil holder securing the TMS coil to the scanner bed. The TMS coil position on the left OFC was determined using the standardized international 10-20 EEG system (with FP1). Participants were scanned in a 3T Siemens Prisma MR scanner in the Core for Advanced MR Imaging at Baylor College of Medicine. Three runs of interleaved TMS-fMRI were acquired using the Multi-Echo EPI sequence (TR/TE1/TE2/TE3 = 2000/23.4/61.26/99.12 ms, 2.75 mm isotropic voxels, FOV = 210 mm). To generate brief periods of neural activity, single TMS pulses were delivered during a 250ms gap between volumes, and participants received a total of 60 single TMS pulses. Interleaved TMS-fMRI data was preprocessed with a standard pipeline in MNI space using AFNI. AFNI's 3dttest+ function was utilized to test the average estimate in a group level analysis.
Results:
Average scores of PHQ-9, SBQ-9, and WHO-ASSIST total were 1.86 (± 2.25), 1.57 (± 2.87), and 10.21 (± 7.66), respectively, which indicate participants had minimal or low severity of psychiatric symptoms. All participants showed negative urine drug tests. Group-wise average resting motor threshold (rMT) was 74% (±10.24) of the maximum stimulator output. Figure 1 shows the group average of brain responses to the TMS effects of OFC stimulation. The results of a whole-brain analysis revealed that single TMS pulses to the left OFC could evoke brain responses in specific brain regions, including the right middle frontal gyrus, anterior and posterior cingulate cortex, bilateral caudate, putamen, and amygdala, and precuneus (FDR-corrected q < 0.01).
·Figure 1. The result of the group average involving brain responses to the TMS effects of OFC stimulation
Conclusions:
In this study, we administered single TMS pulses to investigate the direct effects of TMS stimulation on the left OFC. Our findings suggest that the left OFC could serve as a potential target for TMS intervention in psychiatric disorders, including SUD and depression. Future studies will explore the clinical application of repetitive TMS (rTMS) for patients with SUD.
Brain Stimulation:
Non-invasive Magnetic/TMS
TMS 1
Disorders of the Nervous System:
Psychiatric (eg. Depression, Anxiety, Schizophrenia)
Modeling and Analysis Methods:
Activation (eg. BOLD task-fMRI) 2
Novel Imaging Acquisition Methods:
BOLD fMRI
Keywords:
Addictions
FUNCTIONAL MRI
Limbic Systems
MRI
Psychiatric
Psychiatric Disorders
Sub-Cortical
Transcranial Magnetic Stimulation (TMS)
1|2Indicates the priority used for review
Provide references using author date format
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