Training of visual attentional tracking modulates fronto-parietal activation and cross-modal GABAergic suppression

Visual attention can be employed to track independently moving objects. Such visual attentional tracking (VAT) is associated with fronto-parietal activation and also with cross-modal suppression of activation in the vestibular sensory system to minimize conflicts between vestibular and visual motion cues during VAT. Whether training to improve VAT modulates fronto-parietal activation and cross-modal vestibular suppression remains unclear. Such training might either lead to greater engagement of the visual attention system and thus greater fronto-parietal activation and cross-modal suppression, or it might be associated with a disengagement and thus decreased fronto-parietal activation and cross-modal suppression. We employed a VAT paradigm in which participants were asked to track four target disks among eight distractor disks for a total of 14s. Targets were only highlighted at trial start but were physically undistinguishable from distractors during tracking. At trial end participants were asked to indicate whether a randomly chosen disk was a target or a distractor. Participants (n=16) practiced the task over the course of 30min-long daily training sessions and reached a response accuracy of 90% correct, on average, after seven training sessions. This performance improvement was stable over the course of a one-month-long interval without any training. In a follow-up imaging experiment, a new group of participants (n=12) practiced the same VAT task behaviorally and was scanned with functional MRI and magnetic resonance spectroscopy before and after training. After training, fronto-parietal BOLD-activation decreased during VAT, while at the same time the magnitude of cross-modal suppression also decreased, as shown by a reduction of the concentration of GABA, a chief inhibitory neurotransmitter, during VAT in the vestibular cortex. Taken together, we find that training leads to long-lasting improvements of VAT that are associated with decreased fronto-parietal activation and cross-modal vestibular suppression, indicating that the visual attention system becomes less engaged with training of VAT.