Coping with spatial attention in real space: a low-cost portable testing system for the investigation of visuo-spatial processing in the human brain.

While two-dimensional stimuli may be easily presented with any computer, an apparatus which allows a range of stimuli to be presented in three dimensions is not easily or cheaply available to researchers or clinicians. To fill this gap, we have developed the Realspace Testing System (RTS) which addresses the need for a flexible and multimodal stimulus presentation system capable of displaying stimuli in a three-dimensional space with a high degree of temporal accuracy. The RTS is able to control 26 channels of visual or audio stimuli, to send trigger pulses during each trial to external devices, such as a transcranial magnetic stimulator, and to record subject responses during the testing sessions. The RTS is flexible, portable and can be used in laboratory or clinical settings as required while being built at a low cost using off the shelf components. We have tested the RTS by performing an exploratory experiment on the role of right posterior parietal cortex in visuo-spatial processing in conjunction with online transcranial magnetic stimulation (TMS) and verified that the system can accurately present stimuli as needed while triggering a TMS pulse during each trial at the required time. The RTS could be appealing and useful to a range of researchers or clinicians who may choose to use it much as we have designed it, or use it in its current state as a starting point to customize their stimulus control systems in real space.