Objective Current Brain-Computer Interface (BCI) systems typically flash an array of items from grey to white (GW). The objective of this study was to evaluate BCI performance using uniquely colored stimuli. Methods In addition to the GW stimuli, the current study tested two types of color stimuli (grey to color [GC] and color intensification [CI]). The main hypotheses were that in a checkboard paradigm, unique color stimuli will: (1) increase BCI performance over the standard GW paradigm; (2) elicit larger event-related potentials (ERPs); and, (3) improve offline performance with an electrode selection algorithm (i.e., Jumpwise). Results Online results (n = 36) showed that GC provides higher accuracy and information transfer rate than the CI and GW conditions. Waveform analysis showed that GC produced higher amplitude ERPs than CI and GW. Information transfer rate was improved by the Jumpwise-selected channel locations in all conditions. Conclusions Unique color stimuli (GC) improved BCI performance and enhanced ERPs. Jumpwise-selected electrode locations improved offline performance. Significance These results show that in a checkerboard paradigm, unique color stimuli increase BCI performance, are preferred by participants, and are important to the design of end-user applications; thus, could lead to an increase in end-user performance and acceptance of BCI technology.

A biological marker of the addictive state would be a major breakthrough in objectively assessing the efficacy of treatment outcomes. Given its role in the mesolimbic system and drug reward, most biological marker studies for addiction focus on measures related to dopamine (DA). Dopamine is also implicated in some disorders of visual attention and plays a modulatory role in the processing of color in the retinal DA pathway. For example, visual processing in the retina has been shown to co-vary with DA levels during cocaine withdrawal. In this electroencephalographic (EEG) study, we studied event related potentials (ERPs) and reaction time (RT) in opiate addicts—recruited from a community-based high intensity residential substance abuse and detoxification treatment program—and their age- and gender- matched controls. Using a visual color recognition Go/NoGo task with three similar blocks, participants responded in each block to a "Relevant" stimulus of one of three randomly-presented Red, Green or Blue light stimuli as instructed, while ignoring the other two "Irrelevant" stimuli. This simple task produced robust ERPs that were well-differentiated in the visual evoked potentials (VEPs) obtained by the Relevant stimulus compared to the VEPs from Irrelevant distractor stimuli. P300 ERP amplitudes from the color recognition task were significantly higher in males than females. Similar results were obtained with the frontal late positive (LP) potentials (i.e., 700 msec after stimulus onset), which occurred 200-300 msec after the average participant response/RT. While there were no significant RT differences between controls and addicts in the task, male controls had significantly greater P300 and LP potentials than female controls, suggesting sex differences in visual color processing. However, there were also significant differences in P300 amplitudes male controls and addiction participants—suggesting a difference in retinal DA production in opiate addiction. Further to the hypothesis of sex differences in visual color processing, P300s and LPs were not significantly different in female controls compared to female addicts. Changing the color wavelength of the Relevant stimulus did not significantly affect ERPs in males or females, controls or addicts at P300 but did at LP, particularly when the color blue was relevant. These findings suggest that there are significant sex differences in retinal DA production for opiate addicts and controls in visual processing for a simple Go/NoGo color recognition task.

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