Goal-directed visual information processing with GABAergic inhibition in parietal cortex

Goal-directed visual information processing involves tracking relevant visual signals (targets) over space and time. However, goal-irrelevant visual signals (distractors) can interfere with the tracking of targets. The neuronal mechanisms, which promote the tracking of targets in the challenge of interference from distractors remain elusive. Here, we used time-resolved functional magnetic resonance spectroscopy (fMRS) to measure dynamic changes of γ-aminobutyric acid (GABA), a chief inhibitory neurotransmitter, and glutamate, a chief excitatory neurotransmitter, in the parietal and visual cortices while participants performed a visual tracking task for targets among distractors. We found that the more targets had to be tracked, the greater the concentrations of GABA and glutamate in parietal cortex. In visual cortex only the concentration of glutamate increased with the number of tracking targets. Concentration changes of GABA and glutamate in parietal cortex only were differentially associated with performance: Better target tracking was associated with greater increase in GABA concentration and smaller increase in glutamate concentration. These results suggest that GABAergic inhibition in parietal cortex plays a crucial role in minimizing interference during target tracking over space and time, thereby promoting goal-directed visual information processing.