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Influence of area V5/MT on the task-dependent modulation of subcortical sensory thalamus during visual-speech recognition

Poster D69 in Poster Session D, Wednesday, October 25, 4:45 - 6:30 pm CEST, Espace Vieux-Port

Lisa Jeschke¹, Katharina von Kriegstein¹; ¹Technische Universität Dresden, Germany

There is evidence that sensory thalamus responses are modulated when humans recognise speech and that this task-dependent modulation is behaviourally relevant. We have previously interpreted these findings within a dynamic predictive coding model of cortico-thalamic interactions. In the context of visual speech recognition, one key prediction of the model is that a reduction in the function of relevant visual cortical regions leads to a reduction in the task-dependent modulation of the lateral geniculate nucleus (LGN, visual thalamus) and in the visual speech recognition performance (lip-reading). Here, we investigated whether the cortical area V5/MT, that is highly sensitive to visual motion and has direct connections to the LGN, might be a source of the task-dependent LGN modulation. In the current study, we carried out offline inhibitory transcranial magnetic stimulation (TMS) over area V5/MT or the vertex as active control region on 25 participants. The TMS was followed by functional MRI. Participants were presented with an identical series of stimuli displaying videos of a muted speaker uttering short syllables and, depending on the task instruction, performed a visual speech recognition task or a facial colour recognition task. We hypothesized that a V5/MT stimulation would lower the task-dependent LGN modulation compared to vertex stimulation. Here, we present first preliminary results. Our findings provide new insights into the neural mechanisms, especially the importance of subcortical structures, which support the perception of human communication signals that will help guide future research in typically developed individuals and populations with communication difficulties.

Topic Areas: Speech Perception,