Interactions of Area V5/MT and the Lateral Geniculate Nucleus in the Context of Visual Speech Recognition

Lisa Jeschke

AutorIn

Lisa Jeschke

Titel

Interactions of Area V5/MT and the Lateral Geniculate Nucleus in the Context of Visual Speech Recognition

Zitierfähige Url:

https://nbn-resolving.org/urn:nbn:de:bsz:14-qucosa2-1009007

Erstveröffentlichung

2025

Datum der Einreichung

27.10.2025

Datum der Verteidigung

03.12.2025

Abstract (EN)

The human ability to recognize speech from visual input alone, commonly referred to as visual speech recognition, lipreading or speechreading, relies on complex neural mechanisms that extend beyond classical feedforward processing streams in the visual system. While considerable research has studied cortical contributions to visual speech recognition, much less is known about the role of early visual structures and their modulation through corticothalamic feedback. This thesis addresses this gap by combining transcranial magnetic stimulation (TMS) and functional magnetic resonance imaging (fMRI) to investigate the contribution of V5/MT and the lateral geniculate nucleus (LGN) during visual speech recognition. Across three empirical studies, I first demonstrate that inhibitory stimulation over V5/MT significantly reduces performance in individuals’ visual speech recognition, establishing a causal role of this motion-sensitive region. Second, I investigate the task-dependent stimulation of the LGN and show that response differences between a visual speech task and a colour task, during identical stimuli, are reduced following V5/MT inhibition, indicating that corticothalamic feedback mediates early thalamic processing in humans during active visual perception. However, I did not find a behavioural specificity of this pattern to visual speech recognition. Third, complementary functional connectivity analyses reveal task-dependent interactions between V5/MT and LGN. Together, my findings demonstrate a causal role of V5/MT in visual speech recognition and suggest that corticothalamic feedback to the LGN supports task-dependent visual processing. This work advances our understanding of how cortical and thalamic structures cooperate during complex visual cognition including visual speech recognition. My thesis highlights the importance of feedback mechanisms in shaping early sensory processing and how stimulus parameters and speech-relevant components are implemented in the visual system.

Verweis