SSVEP-modulation by covert and overt attention: Novel features for BCI in attention neuro-rehabilitation

Abstract

In this pilot study the effect of attention (covert and overt) on the signal detection and classification of steady-state visual-evoked potential (SSVEP) were investigated. Using the SSVEP-based paradigm, data were acquired from 4 subjects using 3 scalp electroencephalography (EEG) electrodes located on the visual area. Subjects were instructed to perform the attention task in which they attended covertly or overtly to either of the stimuli flickering with different frequencies (6, 7, 8 and 9Hz). We observed a decrease in signal power in covert compared to the overt attention. However, there was a consistent pattern in covert attention causing an increase in the power of the 2(nd) harmonic of the attended frequency. Encouraging results of this preliminary study indicates that it can be adapted and implemented in the brain-computer interface (BCI) system which could potentially be used as a neuro-rehabilitation tool for individuals with attention deficit.

Transcranial direct-current stimulation modulates offline visual oscillatory activity: A magnetoencephalography study

“…Unfortunately, the functional role of the second and higher-order harmonics remains elusive, and most paradigms involving harmonic responses to date uses them as a stimulus-tagging method (Andersen, Fuchs, & Muller, 2011; Andersen, Muller, & Hillyard, 2015; J. Ding, Sperling, & Srinivasan, 2006; Itthipuripat, Garcia, & Serences, 2013; Muller et al, 2006; Ordikhani-Seyedlar, Sorensen, Kjaer, Siebner, & Puthusserypady, 2014; Scherbaum, Frisch, & Dshemuchadse, 2016; Toffanin, de Jong, Johnson, & Martens, 2009), with little discussion of their specific role in brain function. Nonetheless, taken together it is possible that the basal increase in absolute alpha amplitude, while not directly affecting the induced alpha oscillatory response amplitude, might have impeded the simultaneous entrainment of neurons to fundamental and harmonic frequencies.…”

Investigating overt and covert shifts of attention within social naturalistic scenes

“…For instance, electrophysiological studies using steady-state visual evoked potentials (SSVEPs) have shown worse task performance (i.e., higher error rates and worse classification) and lower SSVEP amplitudes when eye movements were disallowed as opposed to when they were permitted (e.g., Kelly, Lalor, Finucane, & Reilly, 2004;Treder & Blankertz, 2010), suggesting that overt and covert orienting processes can be dissociated. Specifically, there seems to be a decrease in signal power in covert compared to overt attention (Ordikhani-Seyedlar, Sorensen, Kjaer, & Siebner, 2014). Overt attention reflected respective SSVEP frequency entrainment in the primary visual cortex, and covert attention initiated a shift toward parietal and frontal areas, that is, recruiting higher cognitive functions.…”

“…These deviating results raise questions about the dissociation between these two attention mechanisms. The previously mentioned studies that directly compared covert and overt attention mainly investigated general attentional mechanisms by using simplistic stimuli, such as geometric shapes (De Haan et al, 2008;Fairhall et al, 2016;Ordikhani-Seyedlar et al, 2014) or checkerboards (Kelly et al, 2004). Only few studies have compared overt and covert attention in parallel in a social context (e.g., Domes et al, 2013) of which even fewer engaged naturalistic stimuli.…”

Neurofeedback Therapy for Enhancing Visual Attention: State-of-the-Art and Challenges

“…Harmonics of the flickering frequency in some cases give a better BCI readout (Muller-Putz and Pfurtscheller, 2008 ; Allison et al, 2010 ; Ordikhani-Seyedlar et al, 2014 ). Müller-Putz and his colleagues reported particularly good results when they used three harmonic peaks (Muller-Putz et al, 2005 ).…”