Abstract
We studied the causal involvement of area MT+ in an optic flow paradigm. Firstly, we explored the performance of 15 schizophrenic patients and age-matched controls in a task that assessed the local and global contributions to trajectory perception of a moving probe in an optic flow field. Schizophrenic patients showed a significantly reduced bias in trajectory perception for global motion processing only. Secondly we studied the effects of non-invasive transcranial electric stimulation (TES) over the MT+ region. We hypothesized that TES would interfere with processing in the MT+ by modulating spatial suppression of global motion signals. Participants indicated the direction of the moving probe in the global or local optic flow task, while receiving 20 minutes of anodal, cathodal, HF-RNS or sham TES stimulation at 1.5 mA over right MT+ region and right ATL region (control site). We found that cathodal and HF-RNS stimulation over MT+ region had opposite effects on trajectory perception in global optic flow condition. While HF-RNS stimulation reduced the bias of trajectory perception, cathodal stimulation increased it. In summary, we demonstrate the high specificity of brain stimulation over area MT+, since stimulation applied over the ATL, a brain area that is not involved in processing optic flow, was ineffective. Using HF-RNS stimulation over area MT+, we show that the behavioural pattern seen in patients with schizophrenia can be mirrored in neurologically intact participants. Specifically, we show that temporary interference with neural processing in area MT+ produces a selective impairment of global motion processing. In the future, the stimulation effects observed in this study could be combined with perceptual training paradigms to improve motion perception in patients with magnocellular deficits.
Meeting abstract presented at VSS 2016