Callosal anisotropy predicts attentional network changes after parietal inhibitory stimulation

Area of Science:

• Neuroscience
• Cognitive Psychology
• Neuroimaging

Background:

• Hemispatial neglect is linked to disrupted interhemispheric balance, with right hemisphere lesions causing deactivation of the right frontoparietal network.
• Inhibitory transcranial magnetic stimulation (TMS) over the right posterior parietal cortex (PPC) in healthy subjects induces neglect-like, rightward visuospatial bias.

Purpose of the Study:

• To investigate how inhibitory TMS over the right PPC affects resting-state functional connectivity (RSFC) within visuospatial attention networks.
• To explore the relationship between structural white matter properties and TMS-induced changes in RSFC.

Main Methods:

• Healthy participants underwent continuous theta burst TMS over the right PPC and a vertex control condition in a crossover design.
• Resting-state functional connectivity (RSFC) and diffusion-weighted imaging (DWI) were used to assess brain network changes and white matter integrity.

Main Results:

• Right PPC TMS induced a rightward shift in line bisection judgment, indicating a visuospatial bias.
• TMS increased RSFC between the right PPC and the left superior temporal gyrus, suggesting altered attentional network connectivity.
• This connectivity change was inversely related to fractional anisotropy (FA) in the posterior corpus callosum.

Conclusions:

• Local inhibition of the right PPC reshapes functional connectivity within the attentional network.
• Interhemispheric connections, particularly through the corpus callosum, are crucial for mediating the effects of right PPC stimulation on visuospatial attention.