MODALITY-DEPENDENT ROLES OF POSTERIOR PARIETAL CORTEX IN ATTENTIONAL LOCUS AND MOTOR PREPARATION

Extensive evidence indicates that the posterior parietal cortex (PPC) plays a role in integrating sensory information for motor planning. However, its differential involvement in audio–motor versus visuo–motor transformations remains unclear. This study examined how PPC network dynamics differ when attention is directed to auditory or visual stimuli, despite identical audiovisual input. Nineteen participants performed a Go/NoGo task in which they alternately attended to auditory or visual stimuli. On each trial, a 500-ms tone was presented to the left/right ear concurrently with a visual circle displayed on the left/right side of the monitor. Subjects were instructed to quickly respond to the indicated modal stimulus on the left/right side using the corresponding hand for unilateral attended stimuli (Go-trials). For bilateral presentations (NoGo-trials), they were instructed to withhold their responses. Behavioral results showed significantly faster reaction times during visual attention compared to auditory attention. Electroencephalography data were analyzed using phase transfer entropy (PTE) to estimate directed functional connectivity, from which directional global efficiency (GE) was computed to assess large-scale network integration across predefined cortical regions. PTE revealed a significant PPC-to-motor causal influence within 300–400 ms post-stimulus during Go trials, where visual attention produced stronger PPC-driven connectivity. The PPC-to-motor GE demonstrated a significant linear correlation with reaction time in the visual attention task (r=0.49, p<0.05). This suggests that quicker responses in visual attention were associated with reduced network integration. These findings imply modality-specific modulation of PPC-to-motor network dynamics, highlighting the functional role of PPC-driven connectivity in attentional control and action execution.