P104 The role of IPS and TPJ in selective attention in multi-target environments

Abstract

The ability to attend and respond to multiple targets simultaneously is essential for succesful navigation in everyday highly dynamic multi-target environments like traffic scenes. The existing literature suggests a critical role for both the right temporo-parietal junction (TPJ) and the right intraparietal sulcus (IPS) in the ability to attend and respond to multiple targets simultaneously, however, the precise role of each of these areas in this ability is currently unclear. In this study we combined the Theory of Visual Attention (TVA) with continuous theta burst stimulation (cTBS) in neurologically healthy subjects to directly investigate the role of the right IPS and TPJ in attentional selection in multi-target environments. Specifically, we investigated the TVA parameters impaired after a temporary inhibition of neural activity at either the right TPJ or the right IPS and the relation of these TVA parameters to the ability to attend and respond to multiple targets simultaneously. Additionally, in light of recent findings that suggest that cTBS effects on neuronal activity can be highly variable over individuals, we measured the effect of cTBS to the motor cortex on the motor evoked potential (MEP) in each subject to obtain an individual estimate of the presence or absence of inhibitory effects on neuronal activity following cTBS. Our results suggest that cTBS to the IPS elicited a reduction of attentional capacity, the strength of which correlated with the ability to attend and respond to multiple targets simultaneously. Interestingly, this effect was only present in those individuals in whom cTBS to the motor cortex elicited an inhibitory effect on neuronal activity as indicated by reduced MEPs. We found no evidence that cTBS to the TPJ modulated any of the TVA parameters. We conclude that the right IPS may critically modulate attention in multi-target environments via attentional capacity. Moreover, our results suggest that individually determining the effect of cTBS to the motor cortex on neuronal activity may provide meaningful information concerning the presence or absence of inhibitory effects following cTBS also in cortical areas beyond the motor cortex.