The role of the parietal cortex in inhibitory processing in the vertical meridian: Evidence from elderly brain damaged patients

We explored the effects of parietal damage on inhibitory effects of visuospatial attention, inhibition of return (IOR) and inhibitory tagging (IT), in the vertical meridian. We combined a vertical spatial cue paradigm with a Stroop task employing three different temporal intervals between the spatial cue and the target (700, 1200 and 2000 ms) in two groups of patients, one with damage to the parietal cortex and underlying white matter (the parietal patients group) and the other with damage in other brain areas not including the parietal lobe (the control patient group), and a healthy control group. Healthy controls showed the expected inhibitory effects, IOR at the 700 and 1200 intervals and IT at the 1200 interval (as evidenced in a reduction in the magnitude of Stroop interference at the cued location). On the other hand, only the group of parietal patients showed delayed onset of inhibitory effects, IOR and IT appeared at the 1200 ms and 2000 ms intervals, respectively. These findings provide evidence for a role of the parietal cortex, and the underlying fibre tracts, in inhibitory processing in the vertical meridian, with damage to the parietal cortex altering the time course of attention-dependent inhibition.