Chronometric interleaved TMS-fMRI shows state-dependent network effects underlying speech production

Area of Science:

• Neuroscience
• Cognitive Science
• Speech Processing

Background:

• Speech production involves complex cortical networks.
• Causal dynamics within speech networks are not fully understood.
• The temporal specificity of transcranial magnetic stimulation (TMS) effects on speech is unclear.

Purpose of the Study:

• To investigate the causal role of specific brain regions in speech production.
• To explore how the timing of TMS during speech impacts behavior and neural activity.
• To challenge the traditional
• virtual lesion
• model of TMS.

Main Methods:

• Developed a novel chronometric interleaved TMS-fMRI paradigm.
• Delivered TMS to the left superior temporal gyrus (STG) during object naming.
• Stimulated during early conceptual and later linguistic processing stages, recording BOLD responses.

Main Results:

• TMS during linguistic processing caused speech arrest and increased activation in language areas (IFG, STG).
• Stimulation during conceptual processing had minimal neural effects.
• Speech disruption resulted from state-dependent overactivation, not suppression.

Conclusions:

• TMS can amplify neural activity in a state-dependent manner, challenging the
• virtual lesion
• view.
• Established a novel framework for temporally precise causal mapping of speech networks.
• Highlighted the critical role of cognitive state in brain responses to stimulation.