@article{GrussWieserSchweinbergeretal.2012,
  author    = {Gruss, L. Forest and Wieser, Matthias J. and Schweinberger, Stefan R. and Keil, Andreas},
  title     = {Face-evoked steady-state visual potentials: effects of presentation rate and face inversion},
  series = {Frontiers in Human Neuroscience},
  volume    = {6},
  journal   = {Frontiers in Human Neuroscience},
  number    = {316},
  doi       = {10.3389/fnhum.2012.00316},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-134399},
  year      = {2012},
  abstract  = {Face processing can be explored using electrophysiological methods. Research with event-related potentials has demonstrated the so-called face inversion effect, in which the N170 component is enhanced in amplitude and latency to inverted, compared to upright, faces. The present study explored the extent to which repetitive lower-level visual cortical engagement, reflected in flicker steady-state visual evoked potentials (ssVEPs), shows similar amplitude enhancement to face inversion. We also asked if inversion-related ssVEP modulation would be dependent on the stimulation rate at which upright and inverted faces were flickered. To this end, multiple tagging frequencies were used (5, 10, 15, and 20 Hz) across two studies (n=21, n=18). Results showed that amplitude enhancement of the ssVEP for inverted faces was found solely at higher stimulation frequencies (15 and 20 Hz). By contrast, lower frequency ssVEPs did not show this inversion effect. These findings suggest that stimulation frequency affects the sensitivity of ssVEPs to face inversion.},
  language  = {en}
}
@article{JinAllisonKaufmannetal.2012,
  author    = {Jin, Jing and Allison, Brendan Z. and Kaufmann, Tobias and K{\"u}bler, Andrea and Zhang, Yu and Wang, Xingyu and Cichocki, Andrzej},
  title     = {The Changing Face of P300 BCIs: A Comparison of Stimulus Changes in a P300 BCI Involving Faces, Emotion, and Movement},
  series = {PLoS One},
  volume    = {7},
  journal   = {PLoS One},
  number    = {11},
  doi       = {10.1371/journal.pone.0049688},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-134173},
  pages     = {e49688},
  year      = {2012},
  abstract  = {Background: One of the most common types of brain-computer interfaces (BCIs) is called a P300 BCI, since it relies on the P300 and other event-related potentials (ERPs). In the canonical P300 BCI approach, items on a monitor flash briefly to elicit the necessary ERPs. Very recent work has shown that this approach may yield lower performance than alternate paradigms in which the items do not flash but instead change in other ways, such as moving, changing colour or changing to characters overlaid with faces. Methodology/Principal Findings: The present study sought to extend this research direction by parametrically comparing different ways to change items in a P300 BCI. Healthy subjects used a P300 BCI across six different conditions. Three conditions were similar to our prior work, providing the first direct comparison of characters flashing, moving, and changing to faces. Three new conditions also explored facial motion and emotional expression. The six conditions were compared across objective measures such as classification accuracy and bit rate as well as subjective measures such as perceived difficulty. In line with recent studies, our results indicated that the character flash condition resulted in the lowest accuracy and bit rate. All four face conditions (mean accuracy >91\%) yielded significantly better performance than the flash condition (mean accuracy = 75\%). Conclusions/Significance: Objective results reaffirmed that the face paradigm is superior to the canonical flash approach that has dominated P300 BCIs for over 20 years. The subjective reports indicated that the conditions that yielded better performance were not considered especially burdensome. Therefore, although further work is needed to identify which face paradigm is best, it is clear that the canonical flash approach should be replaced with a face paradigm when aiming at increasing bit rate. However, the face paradigm has to be further explored with practical applications particularly with locked-in patients.},
  language  = {en}
}