Resting-State Functional Connectivity Differences Following Experimental Manipulation of the Orbitofrontal Cortex in Two Directions via Theta-Burst Stimulation

Compulsive behaviors (CBs) have been linked to orbitofrontal cortex (OFC) function in animal and human studies. However, brain regions function not in isolation but as components of widely distributed brain networks—such as those indexed via resting-state functional connectivity (RSFC). Sixty-nine individuals with CB disorders were randomized to receive a single session of neuromodulation targeting the left OFC—intermittent theta-burst stimulation (iTBS) or continuous TBS (cTBS)—followed immediately by computer-based behavioral “habit override” training. OFC seeds were used to quantify RSFC following iTBS and following cTBS. Relative to cTBS, iTBS showed increased RSFC between right OFC (Brodmann’s area 47) and other areas, including dorsomedial prefrontal cortex (dmPFC), occipital cortex, and a priori dorsal and ventral striatal regions. RSFC connectivity effects were correlated with OFC/frontopolar target engagement and with subjective difficulty during habit-override training. Findings help reveal neural network-level impacts of neuromodulation paired with a specific behavioral context, informing mechanistic intervention development.

Using Neurofeedback from Steady-State Visual Evoked Potentials to Target Affect-Biased Attention in Augmented Reality

Biases in attention to emotional stimuli (i.e., affect-biased attention) contribute to the development and mainte-nance of depression and anxiety and may be a promising target for intervention. Past attempts to therapeutically modify affect-biased attention have been unsatisfactory due to issues with reliability and precision. Electroencephalogram (EEG)-derived steady-state visual evoked potentials (SSVEPS) provide a temporally-sensitive biological index of attention to competing visual stimuli at the level of neuronal populations in the visual cortex. SSVEPS can potentially be used to quantify whether affective distractors vs. task-relevant stimuli have "won" the competition for attention at a trial-by-trial level during neuro-feedback sessions. This study piloted a protocol for a SSVEP-based neurofeedback training to modify affect-biased attention using a portable augmented-reality (AR) EEG interface. During neurofeedback sessions with five healthy participants, signifi-cantly greater attention was given to the task-relevant stimulus (a Gabor patch) than to affective distractors (negative emotional expressions) across SSVEP indices (p<0.000l). SSVEP indices exhibited excellent internal consistency as evidenced by a maximum Guttman split-half coefficient of 0.97 when comparing even to odd trials. Further testing is required, but findings suggest several SSVEP neurofeedback calculation methods most deserving of additional investigation and support ongoing efforts to develop and implement a SSVEP-guided AR-based neurofeedback training to modify affect-biased attention in adolescent girls at high risk for depression.

A double-blind study assessing the impact of orbitofrontal theta burst stimulation on goal-directed behavior

Patients with disorders of compulsivity show impairments in goal-directed behavior, which have been linked to orbitofrontal cortex (OFC) dysfunction. We recently showed that continuous theta burst stimulation (cTBS), which reduces OFC activity, had a beneficial effect on compulsive behaviors both immediately and at 1 week follow-up compared with inhibitory TBS (iTBS). In this same sample, we investigated whether two behavioral measures of goal-directed control (devaluation success on a habit override task; model-based planning on the two-step task) were also affected by acute modulation of OFC activity. Overall, model-based planning and devaluation success were significantly related to each other and (for devaluation success) to symptoms in our transdiagnostic clinical sample. These measures were moderately to highly stable across time. In individuals with low levels of model-based planning, active cTBS improved devaluation success. Analogous to previously reported clinical effects, this effect was specific to cTBS and not iTBS. Overall, results suggested that measures of goal directed behavior are reliable but less affected by cTBS than clinical self-report. Future research should continue to examine longitudinal changes in behavioral measures to determine their temporal relationship with symptom improvement after treatment. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Racial Stress and Trauma and the Development of Adolescent Depression: A Review of the Role of Vigilance Evoked by Racism-Related Threat

There are known disparities in the burden of illness and access/quality of care for African, Latino/a, Asian, and Native American (ALANA) patients diagnosed with depressive disorders, which may occur because of health inequities. Racial stress and trauma (RST), or the significant fear and distress that can be imparted from exposure to racism, is one such inequity linked to the development of depression. The current review summarizes past research examining the association between racism, RST, and depression, as well as avenues in which RST becomes biologically embedded in ALANA individuals. We describe multimodal research that supports vigilance as a potential mediator of the association between RST and depression and consider the nuanced role that vigilance plays during experiences with racism. Finally, we describe methodological advances in the assessment of vigilance evoked by RST and the clinical implications that may be generated by future improvements. In each of these areas, we present examples of how ongoing and future research can be leveraged to provide support for psychosocial programs that facilitate autonomous community healing and resilience, increase calls for public policy changes, and support clinical interventions that lessen the burden of racism on ALANA communities.

Effect of Experimental Manipulation of the Orbitofrontal Cortex on Short-Term Markers of Compulsive Behavior: A Theta Burst Stimulation Study

OBJECTIVE

Compulsive behaviors are a core feature of obsessive-compulsive spectrum disorders but appear across a broad spectrum of psychological conditions. It is thought that compulsions reflect a failure to override habitual behaviors "stamped in" through repeated practice and short-term distress reduction. Animal models suggest a possible causal role of the orbitofrontal cortex (OFC) in compulsive behaviors, but human studies have largely been limited by correlational designs. The goal of this study was to establish the first experimental evidence in humans for a mechanistic model in order to inform further experimental work and the eventual development of novel mechanistic treatments involving synergistic biological-behavioral pairings.

METHODS

After a baseline assessment, 69 individuals with compulsive behavior disorders were randomly assigned, in a double-blind, between-subjects design, to receive a single session of one of two active stimulation conditions targeting the left OFC: intermittent theta burst stimulation (iTBS), expected to increase OFC activity, or continuous TBS (cTBS), expected to decrease activity (both conditions, 600 pulses at 110% of target resting motor threshold). In both conditions, brain modulation was paired with a subsequent computer task providing practice in overriding a clinically relevant habit (an overlearned shock avoidance behavior), delivered during the expected window of OFC increase or decrease. Pre- and post-TBS functional MRI assessments were conducted of target engagement and compulsive behaviors performed in response to an idiographically designed stressful laboratory probe.

RESULTS

cTBS and iTBS modulated OFC activation in the expected directions. cTBS, relative to iTBS, exhibited a beneficial impact on acute laboratory assessments of compulsive behaviors 90 minutes after TBS. These acute behavioral effects persisted 1 week after cTBS.

CONCLUSIONS

Experimental modulation of the OFC, within the behavioral context of habit override training, affected short-term markers of compulsive behavior vulnerability. The findings help delineate a causal translational model, serving as an initial precursor to mechanistic intervention development.