The Role of the Corpus Callosum in Transcranial Magnetic Stimulation Induced Interhemispheric Signal Propagation

doi:10.1016/j.biopsych.2010.06.021

Biological Psychiatry

Volume 68, Issue 9, 1 November 2010, Pages 825-831

https://doi.org/10.1016/j.biopsych.2010.06.021 Get rights and content

Background

The corpus callosum, the main interhemispheric connection in the brain, may serve to preserve functional asymmetry between homologous cortical regions.

Methods

To test this hypothesis, 30 healthy adult subjects underwent combined transcranial magnetic stimulation (TMS)–electroencephalography procedures. Nineteen of these subjects also completed diffusion tensor imaging and tractography procedures. We examined the relationship between microstructural integrity of subdivisions of the corpus callosum with TMS-induced interhemispheric signal propagation.

Results

We found a significant inverse relationship between microstructural integrity of callosal motor fibers with TMS-induced interhemispheric signal propagation from left to right motor cortex. We also found a significant inverse relationship between microstructural integrity of genu fibers of the corpus callosum and TMS-induced interhemispheric signal propagation from left to right dorsolateral prefrontal cortex (DLPFC). We then demonstrated neuroanatomic specificity of these relationships.

Conclusions

Taken together, our findings suggest that TMS-induced interhemispheric signal propagation is transcallosally mediated and neuroanatomically specific and support a role for the corpus callosum in preservation of functional asymmetry between homologous cortical regions. Delineation of the relationship between corpus callosum microstructure and interhemispheric signal propagation in neuropsychiatric disorders, such as schizophrenia, may reveal novel mechanisms of pathophysiology.

Section snippets

Participants

Thirty right-handed healthy subjects (mean age = 34.0 ± 7.9, range = 20–48 years; 18 males, 12 females) completed TMS-EEG procedures, of whom 19 completed DTI (mean age = 35.7 ± 6.5 years, range = 23–47 years; 14 males, five females). All subjects were recruited via advertisements or self-referral, and psychopathology was ruled out through the Personality Assessment Screener (Psychological Assessment Resources, Lutz, Florida). Exclusion criteria included a self-reported medical illness or a

TMS-EEG

Active suprathreshold stimulation of the left motor cortex resulted in significant activation of the right motor cortex compared with sham (active: 297.1 ± 183.3 μv.msec, sham: 106.1 ± 51.7 μv.msec; t = 5.7, df = 25, p < .001; Figure 2A). In the active condition, activation of the right motor cortex was significantly lower compared with the activity in left motor cortex (right: 291.31 ± 175.54 μv.msec, left: 797.1 ± 536.4 μv.msec; t = 6.0, df = 29, p < .001; Figure 2B). The mean TMS-induced

Discussion

This study represents the first attempt to investigate directly the relationship between ISP of TMS-induced cortical evoked potentials and microstructural integrity of the corpus callosum. Our findings provide in vivo support for the theory that the corpus callosum may serve to limit “excessive crosstalk” between hemispheres when cortical regions are asymmetrically activated. First, there was a significant inverse correlation between TMS-induced ISP in the motor cortex and FA in callosal motor

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: Authors ANV and FF contributed equally to this article.

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Archival ReportThe Role of the Corpus Callosum in Transcranial Magnetic Stimulation Induced Interhemispheric Signal Propagation

Background

Methods

Results

Conclusions

Section snippets

Participants

TMS-EEG

Discussion

Cortex

J Magn Reson B

Neuroimage

Neuroimage

Neuroimage

Neuropsychologia

Electroencephalogr Clin Neurophysiol

Biol Psychiatry

J Neurosci Methods

Neuroimage

Clin Neurophysiol

Med Image Anal

Neuroimage

Neuroimage

Agenesis of the corpus callosum: Genetic, developmental and functional aspects of connectivity

Nat Rev Neurosci

Observations on visual processes after posterior callosal section

Neurology

Hemispheric asymmetry in human lateral prefrontal cortex during cognitive set shifting

Proc Natl Acad Sci U S A

Wisconsin card sorting revisited: Distinct neural circuits participating in different stages of the task identified by event-related functional magnetic resonance imaging

J Neurosci

The basis of anisotropic water diffusion in the nervous system—a technical review

NMR Biomed

The mechanisms of interhemispheric inhibition in the human motor cortex

J Physiol

Long-interval cortical inhibition from the dorsolateral prefrontal cortex: A TMS-EEG study

Neuropsychopharmacology

Archival Report
The Role of the Corpus Callosum in Transcranial Magnetic Stimulation Induced Interhemispheric Signal Propagation