Pharmacological mechanisms of interhemispheric signal propagation: a TMS-EEG study

Hui, Jeanette; Zomorrodi, Reza; Lioumis, Pantelis; Salavati, Bahar; Rajji, Tarek K.; Chen, Robert; Blumberger, Daniel M.; Daskalakis, Zafiris J.

doi:10.1038/s41386-019-0468-7

Cited by 25 publications

(17 citation statements)

References 74 publications

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“…Higher cortical sensory areas in vertebrates are linked through interhemispheric fibers, mostly mediating contralateral hemisphere inhibition [78,79]. In this study, we found a dual component inhibitory and excitatory interhemispheric circuit linking homologous sensory maps.…”

Section: Discussionsupporting

confidence: 50%

Interhemispheric connections between olfactory bulbs improve odor detection

Kermen

Yaksi

2019

Preprint

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SUMMARYInterhemispheric connections enable interaction and integration of sensory information in bilaterian nervous systems and are thought to optimize sensory computations. However, the cellular and spatial organization of interhemispheric networks as well as the computational properties they mediate in vertebrates are still poorly understood. Thus, it remains unclear to which extent the connectivity between left and right brain hemispheres participates in sensory processing. Here, we show that the zebrafish olfactory bulbs (OBs) receive direct interhemispheric projections from their contralateral counterparts in addition to top-down inputs from the contralateral zebrafish homolog of olfactory cortex. The direct interhemispheric projections between the OBs reach peripheral layers of the contralateral OB and retain a fine-grained topographic organization, which directly connects similarly tuned olfactory glomeruli across hemispheres. In contrast, interhemispheric top-down inputs consist of diffuse projections that broadly innervate the inhibitory granule cell layer. Jointly, these interhemispheric connections elicit a balance of topographically organized excitation and non-topographic inhibition on the contralateral OB and modulate odor responses. We show that the interhemispheric connections in the olfactory system enable the modulation of odor response and improve the detection of a reproductive pheromone, when presented together with competing complex olfactory cues, by boosting the response of the pheromone selective neurons. Taken together, our data shows a previously unknown function for an interhemispheric connection between chemosensory maps of the olfactory system.

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Section: Discussionsupporting

confidence: 50%

Interhemispheric connections between olfactory bulbs improve odor detection

Kermen

Yaksi

2019

Preprint

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“…Consequently, excessive inhibition might obstruct spreading of seizure activity to essential parts of the patients’ brain. In support of this, a study using TMS showed that baclofen, a GABA B receptor agonist, reduced interhemispheric signal propagation 38 . Also, previous studies showed that the strength of the post-ictal suppression is associated with ECT effectiveness 21,39 .…”

Section: Discussionmentioning

confidence: 85%

Neural excitation/inhibition imbalance and the treatment of severe depression

Bruin

Zeidman

et al. 2021

Preprint

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An influential hypothesis holds that depression is related to a neural excitation/inhibition imbalance, but its role in the treatment of depression remains unclear. Here, we show that unmedicated patients with severe depression demonstrated reduced inhibition of brain-wide resting-state networks relative to healthy controls. Patients using antidepressants showed inhibition that was higher than unmedicated patients and comparable to controls, but they still suffered from severe depression. Subsequent treatment with electroconvulsive therapy (ECT) reduced depressive symptoms, but its effectiveness did not depend on changes in network inhibition. Concomitant pharmacotherapy increased the effectiveness of ECT, but only when the strength of neural inhibition before ECT was within the normal range and not when inhibition was excessive. These findings suggest that reversing the excitation/inhibition imbalance may not be sufficient nor necessary for the effective treatment of severe depression, and that brain-state informed pharmacotherapy management may enhance the effectiveness of ECT.

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“…A few previous studies investigated the effect of TMS on ISP. Baclofen was shown to increase interhemispheric inhibition [ 58 ], and it was recently shown to decrease ISP in the M1 [ 15 ], establishing a potential link between ISP and interhemispheric inhibition. In addition, Premoli et al [ 13 ] showed that baclofen increased N100 in the stimulated hemisphere only, instead of in bilateral sides.…”

Section: Discussionmentioning

confidence: 99%

“…where t is time, V is the voltage at channel i, and K is the number of channels. ISP was calculated by dividing the area under TEP curves in the left hemisphere by that in the right hemisphere, as it was shown to be reliable in recent studies [15,37]. Theoretically, an ISP value below 100% was expected.…”

Section: Data Processingmentioning

confidence: 99%

“…These studies indicated a strong relationship between later TEP peaks (N45 and N100) and intracortical inhibition mediated by GABA receptors, which may be an underlying mechanism of the late TEP peaks. Most recently, a study by Hui et al showed that baclofen could decrease TMS-induced interhemispheric signal propagation (ISP), probably a potential neurophysiological biomarker reflecting interhemispheric inhibition mediated by GABAB receptors [ 15 ].…”

Section: Introductionmentioning

confidence: 99%

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Intermittent Theta Burst Stimulation to the Primary Motor Cortex Reduces Cortical Inhibition: A TMS-EEG Study

2021

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Introduction: The aim of this study was to reveal the effects of intermittent theta burst stimulation (iTBS) in modulating cortical networks using transcranial magnetic stimulation and electroencephalography (TMS-EEG) recording. Methods: Eighteen young adults participated in our study and received iTBS to the primary motor cortex (M1), supplementary motor area, and the primary visual cortex in three separate sessions. A finger tapping task and ipsilateral single-pulse TMS-EEG recording for the M1 were administrated before and after iTBS in each session. The effects of iTBS in motor performance and TMS-evoked potentials (TEPs) were investigated. Results: The results showed that iTBS to the M1, but not supplementary motor area or the primary visual cortex, significantly reduced the N100 amplitude of M1 TEPs in bilateral hemispheres (p = 0.019), with a more prominent effect in the contralateral hemisphere than in the stimulated hemisphere. Moreover, only iTBS to the M1 decreased global mean field power (corrected ps < 0.05), interhemispheric signal propagation (t = 2.53, p = 0.030), and TMS-induced early α-band synchronization (p = 0.020). Conclusion: Our study confirmed the local and remote after-effects of iTBS in reducing cortical inhibition in the M1. TMS-induced oscillations after iTBS for changed cortical excitability in patients with various neurological and psychiatric conditions are worth further exploration.

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Pharmacological mechanisms of interhemispheric signal propagation: a TMS-EEG study

Cited by 25 publications

References 74 publications

Interhemispheric connections between olfactory bulbs improve odor detection

Interhemispheric connections between olfactory bulbs improve odor detection

Neural excitation/inhibition imbalance and the treatment of severe depression

Intermittent Theta Burst Stimulation to the Primary Motor Cortex Reduces Cortical Inhibition: A TMS-EEG Study

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