### Aims and Hypotheses  
The objective of the current study was to determine whether the application of jittered SOIs would meaningfully affect electrophysiological measures of attention observed during an RSVP paradigm, where attentional responses to discrete stimuli typically overlap with one another, and whether these changes would improve performance of the BCI system. In the context of this investigation, \"attention\" is defined as selective visual attention to the presentation of a target letter stimulus. Likewise, SOI refers to the time elapsed between the onset of two sequential stimuli, which some groups refer to instead as stimulus onset asynchrony (SOA) [11; 26]. Our study analyzed three EEG-based signals known to be evident during RSVP: N200, P300, and alpha attenuation [11; 19]. The N200 and P300 are endogenous ERPs known to reflect contextual deviation and the recognition of target stimuli, respectively [27]. Alpha rhythms are neural oscillations in the approximate range of 8-13 Hz that are thought to result from thalamocortical synchronization [28]. Posterior alpha attenuation is known to correspond with attentional allocation and shifts in visual-spatial attention [29; 30]. All three of these signals are known to show increased response amplitudes to target stimuli, compared to non-target stimuli in RSVP. We hypothesized that N200 and P300 attentional responses would show larger amplitudes in the jittered conditions, compared to non-jittered stimulus presentations. Similarly, we predicted that attentional alpha attenuation responses would be larger for jittered stimulus presentations than for non-jittered presentations. We predicted that machine learning classification of these three attentional markers would improve with the application of jittered SOIs thatdecrease the SSVEP component in averaged ERPs, and that participants would have higher accuracy rates during on-line copy phrase tasks in the jittered conditions.  
Secondary aims of this study included exploratory examinations of individual differences in the alpha attenuation signal, and also measurement of variance in the ERPs. A slowed-down version of the RSVP task was presented at the end of each visit to collect non-overlapping electrophysiological markers, but this task existed as a non-experimental addition only. Results of the slowed-down task are discussed intermittently; however, there is significant difficulty in measuring an experimental baseline effect of stimulus overlap without qualitatively changing the RSVP task (see Section 4.3). To supplement the primary alpha attenuation analysis, we also performed a comparison of \"responder\" and \"non-responder\" groups (see Section 3.7.2). The motivation for expanding our scrutiny of this measure was two-fold: firstly, compared to the literature on the N200 and P300 responses, alpha attenuation in RSVP is less understood. As such, the present investigation is an opportunity to document important characteristics of this measure. Secondly, differences between slow and fast letter presentations in RSVP were much more dramatic for alpha attenuation than for N200 or P300 in a previous report [19], and individual differences have been previously identified as a potential contributing factor to similar alpha measures [19; 31].