P258 Combining tDCS with prismatic adaptation for non invasive neuromodulation of the motor cortex

Introduction: Prismatic adaptation (PA) shifts visual field laterallyand induces lateralized deviations of spatial attention. Recently, ithas been suggested that prismatic goggles are also able to modulatebrain excitability (Magnani, 2014), with cognitive after-effects documentedeven in tasks not necessarily spatial in nature (Oliveri, 2013).Objectives: The aim of the present study was to test whetherprisms can modulate motor cortical excitability similarly as anodaltranscranial direct current stimulation (tDCS) does; to test whetherneuromodulatory effects obtained from tDCS and prismatic gogglescould interact and induce homeostatic changes in brainexcitability.Materials and methods: Twenty-four subjects were submitted tosingle-pulse transcranial magnetic stimulation (TMS) over the rightM1 to measure their Input–Output (IO) curve as a measure of corticalexcitability (Carroll, 2011). Assessment was made in three experimentalgroups: before and after rightward PA; before and afteratDCS of the right M1; before and after rightward PA and atDCS ofthe right M1.Results: A significant increase of the steepness of the IO curveslope on the right motor cortex was found following either rightwardPA or atDCS; on the other hand, a decrease of the steepnessof the IO curve slope was found after the combination of rightwardPA and atDCS.Conclusion: These findings suggest that PA could be an additionaltool to modulate cortical plasticity in motor cortices and that anincrease or a decrease in corticospinal excitability depends on thefunctional state of the M1 before or at the time of conditioning(Lang, 2004).