Dorsal Posterior Parietal Cortex Lesions Disrupt Spatial- but Not Motor-Based Inhibition

Spatial and response inhibition are two different types of inhibition processes. Spatial inhibition refers to the suppression of a specific location, whereas response inhibition involves cancelling a planned movement and is motor based. Here we examined the effects of lesions on the dorsal posterior parietal cortex on performance during two saccade tasks that separately assessed spatial (inhibition of return task) and response inhibition (stop signal task). We tested two stroke patients, one with unilateral and one with bilateral lesions to the dorsal posterior parietal cortex, as well as 21 age-matched controls. In our spatial inhibition task, control participants showed the typical inhibition of return effect, whereas patients exhibited no inhibition of return in their ataxic hemifields. In contrast, patients and their matched controls performed similarly on the stop signal task. These results reveal a simple dissociation in our patients, where motor-based inhibition is preserved following damage to the dorsal posterior parietal cortex, whereas spatial inhibition is impaired. This highlights the specific role of the dorsal posterior parietal cortex in spatial inhibition, notably related to spatial attentional mechanisms.