Continuous theta burst TMS of area MT+ impairs attentive motion tracking

Abstract Attentive motion tracking deficits, measured using multiple object tracking (MOT) tasks, have been identified in a number of visual and neurodevelopmental disorders such as amblyopia and autism. These deficits are often attributed to the abnormal development of high-level attentional networks. However, neuroimaging evidence from amblyopia suggests that reduced MOT performance can be explained by impaired function in motion sensitive area MT+ alone. To test the hypothesis that MT+ plays an important role in MOT, we assessed whether modulation of MT+ activity using continuous theta burst stimulation (cTBS) influenced MOT performance in participants with normal vision. An additional experiment involving numerosity judgements of MOT stimulus elements was conducted to control for non-specific effects of MT+ cTBS on psychophysical task performance. The MOT stimulus consisted of 4 target and 4 distractor dots and was presented at 10° eccentricity in the right or left hemifield. Functional MRI-guided cTBS was applied to left MT+. Participants (n = 13, age:27 ± 3) attended separate active and sham cTBS sessions where the MOT task was completed before, 5 mins post and 30 mins post cTBS. Active cTBS significantly impaired MOT task accuracy relative to baseline for the right (stimulated) hemifield 5 mins (10 ± 2% reduction; t12 = 1.95, p = 0.03) and 30 mins (14 ± 3% reduction; t12 = 2.96, p = 0.01) post stimulation. No impairment occurred within the left (control) hemifield after active cTBS or for either hemifield after sham cTBS. Numerosity task performance was unaffected by cTBS. These results highlight the importance of lower-level motion processing for MOT and suggest that abnormal function of MT+ alone is sufficient to cause a deficit in MOT task performance.