Distinct associations between thalamo-amygdala pathways and state anxiety

Neurobiological models of emotion have proposed the existence of multiple direct subcortical pathways in humans, often referred to as "low roads", linking the thalamus to the amygdala and implicated in affective function. Among these, pulvinar-amygdala structural connectivity has been associated with individual differences in anxiety and anxiety-related conditions. However, whether distinct thalamo-amygdala pathways across thalamic subnuclei differentially relate to anxiety remains unknown. Using diffusion MRI in 34 healthy participants, we reconstructed four candidate subcortical "low roads" bilaterally from the medial geniculate body (MGB), as well as the medial, inferior and lateral pulvinar to the basolateral amygdala (BLA). We then tested whether their structural connectivity strength was associated with individual differences in state and trait anxiety. Linear regression analyses revealed that fiber density in three left thalamo-amygdala pathways predicted state, but not trait, anxiety. Importantly, our results showed a functional dissociation across pathways. While fiber density in MGB-BLA and medial pulvinar-BLA pathways was negatively related to state anxiety, the inferior pulvinar-BLA tract showed the opposite association. These findings support differentiated contributions across thalamo-amygdala pathways in humans to state anxiety. The results highlight these subcortical pathways as potentially relevant neurobiological substrates for understanding anxiety and affective function. Key pointsO_LIFiber density of three left thalamo-amygdala pathways explained 24.1% of the variance in state anxiety across 34 healthy individuals C_LIO_LIFiber density in the left medial geniculate body and left medial pulvinar-amygdala pathways was negatively associated with state anxiety C_LIO_LIFiber density in the left inferior pulvinar-amygdala pathway was positively associated with state anxiety C_LI