Neuroscientists: TMS over V5/MT disrupts thalamus lip-reading responses
Inhibiting visual-motion cortex V5/MT suppresses LGN signals during visual speech tasks
A new study published on arXiv (2608.19034) provides the first causal evidence in humans that visual association cortex feeds back to modulate the sensory thalamus during perception. Researchers led by Lisa Jeschke at TU Dresden applied inhibitory transcranial magnetic stimulation (TMS) over bilateral visual-motion area V5/MT in 26 healthy adults. Participants then performed visual speech recognition and a color control task on muted videos of speaking faces, while brain activity was measured with fMRI.
The results showed that the lateral geniculate nucleus (LGN) had significantly different BOLD responses between speech and color tasks after sham (Vertex) stimulation. However, this task-dependent modulation was markedly reduced after inhibitory V5/MT stimulation. Functional connectivity between V5/MT and LGN also dropped during the speech task. These findings identify corticothalamic feedback as a necessary mechanism for visual processing, specifically showing that higher-order cortex exerts a causal influence over early sensory relay nuclei during lip-reading.
- Inhibitory TMS over V5/MT significantly reduced LGN BOLD response modulation during visual speech vs. color task in 26 adults
- Task-dependent functional connectivity between V5/MT and LGN decreased after TMS, confirming a causal pathway
- Study provides first human causal evidence that visual association cortex modulates sensory thalamus via corticothalamic feedback
Why It Matters
Establishes cortex-thalamus feedback as critical for perception, with implications for brain-stimulation therapies targeting sensory processing disorders.