Continuous Theta Burst Stimulation Over the Right Orbitofrontal Cortex Impairs Conscious Olfactory Perception

Non-invasive brain stimulation is a useful tool to probe brain function and provide therapeutic treatments in disease. When applied to the right posterior parietal cortex (PPC) of healthy participants, it is possible to temporarily shift spatial attention and mimic symptoms of spatial neglect. However, the field of brain stimulation is plagued by issues of high response variability. The aim of this study was to investigate baseline functional connectivity as a predictor of response to an inhibitory brain stimulation paradigm applied to the right PPC. In fourteen healthy adults (9 female, aged 24.8 ± 4.0 years) we applied continuous theta burst stimulation (cTBS) to suppress activity in the right PPC. Resting state functional connectivity was quantified by recording electroencephalography and assessing phase consistency. Spatial attention was assessed before and after cTBS with the Landmark Task. Finally, known determinants of response to brain stimulation were controlled for to enable robust investigation of the influence of resting state connectivity on cTBS response. We observed significant inter-individual variability in the behavioral response to cTBS with 53.8% of participants demonstrating the expected rightward shift in spatial attention. Baseline high beta connectivity between the right PPC, dorsomedial pre-motor region and left temporal-parietal region was strongly associated with cTBS response (R2 = 0.51). Regression analysis combining known cTBS determinants (age, sex, motor threshold, physical activity, stress) found connectivity between the right PPC and left temporal-parietal region was the only significant variable (p = 0.011). These results suggest baseline resting state functional connectivity is a strong predictor of a shift in spatial attention following cTBS. Findings from this study help further understand the mechanism by which cTBS modifies cortical function and could be used to improve the reliability of brain stimulation protocols.

Download Full-text

Continuous theta-burst stimulation of the right superior temporal gyrus impairs self-motion perception

Experimental Brain Research ◽

10.1007/s00221-013-3660-8 ◽

2013 ◽

Vol 230 (3) ◽

pp. 359-370 ◽

Cited By ~ 6

Author(s):

A. A. Tarnutzer ◽

A. G. Lasker ◽

D. S. Zee

Keyword(s):

Motion Perception ◽

Superior Temporal Gyrus ◽

Theta Burst Stimulation ◽

Burst Stimulation ◽

The Right ◽

Self Motion ◽

Theta Burst ◽

Continuous Theta Burst Stimulation ◽

Stimulation Of

Download Full-text

Behavioral effects of continuous theta-burst stimulation in macaque parietal cortex

Scientific Reports ◽

10.1038/s41598-021-83904-8 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Lara Merken ◽

Marco Davare ◽

Peter Janssen ◽

Maria C. Romero

Keyword(s):

Parietal Cortex ◽

High Intensity ◽

Theta Burst Stimulation ◽

Burst Stimulation ◽

Primate Model ◽

Power Grip ◽

Fitts Law ◽

Behavioral Evidence ◽

Theta Burst ◽

Continuous Theta Burst Stimulation

AbstractThe neural mechanisms underlying the effects of continuous Theta-Burst Stimulation (cTBS) in humans are poorly understood. Animal studies can clarify the effects of cTBS on individual neurons, but behavioral evidence is necessary to demonstrate the validity of the animal model. We investigated the behavioral effect of cTBS applied over parietal cortex in rhesus monkeys performing a visually-guided grasping task with two differently sized objects, which required either a power grip or a pad-to-side grip. We used Fitts’ law, predicting shorter grasping times (GT) for large compared to small objects, to investigate cTBS effects on two different grip types. cTBS induced long-lasting object-specific and dose-dependent changes in GT that remained present for up to two hours. High-intensity cTBS increased GTs for a power grip, but shortened GTs for a pad-to-side grip. Thus, high-intensity stimulation strongly reduced the natural GT difference between objects (i.e. the Fitts’ law effect). In contrast, low-intensity cTBS induced the opposite effects on GT. Modifying the coil orientation from the standard 45-degree to a 30-degree angle induced opposite cTBS effects on GT. These findings represent behavioral evidence for the validity of the nonhuman primate model to study the neural underpinnings of non-invasive brain stimulation.

Download Full-text