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Gewählte Publikation:

Publikationstyp: Zeitschriftenaufsatz
Dokumenttyp: Originalarbeit

Jahr: 2012

AutorInnen: Walter, S; Quigley, C; Andersen, SK; Mueller, MM

Titel: Effects of overt and covert attention on the steady-state visual evoked potential.

Quelle: Neurosci Lett. 2012; 519(1):37-41

Autor/innen der Vetmeduni Vienna:

Quigley Cliodhna

Diese Publikation wurde nicht im Namen der Vetmeduni Vienna erstellt und ist deshalb ausschließlich der persönlichen Publikationsliste des/der Autors/Autorin zugeordnet!

Flickering stimuli evoke an oscillatory brain response with the same frequency as the driving stimulus, the so-called steady-state visual evoked potential (SSVEP). SSVEPs are robust brain signals whose amplitudes are enhanced with attention and thus play a major role in the development and use of non-invasive Brain-Computer Interfaces (BCIs). We compared the modulation of SSVEP amplitudes when subjects directly gazed at a flickering array of static dots (overt attention) to when they covertly shifted attention to the dots keeping their eyes at central fixation. A discrimination task was performed at the attended location to ensure that subjects shifted attention as instructed. Horizontal eye movements (allowed in overt attention but to be avoided in covert attention) were monitored by the horizontal electrooculogram. Subjects" behavioural performance was significantly reduced in covert attention compared to overt attention. Correspondingly, attentional modulation of SSVEP amplitudes by overt attention was larger in magnitude than for covert attention. Overt attention also changed the topographical distribution of SSVEP amplitudes on the scalp. Stimuli elicited the largest amplitudes at central occipital electrodes when they were overtly attended and at contralateral parieto-occipital sites when they were covertly attended. Accordingly, source analysis revealed clear centrally located sources in early visual areas in overt attention, regardless of the attended visual hemifield. Taken together these results affirm that overt and covert attention have qualitatively and quantitatively different effects on SSVEP responses as well as on task performance. Moreover, our results suggest that navigating SSVEP-BCIs with overt attention is more reliable and highlight some of the challenges in developing BCIs for patients who have lost the ability to move their eyes.

Keywords Pubmed: Adult
Biological Clocks/physiology*
Evoked Potentials, Visual/physiology*
Fixation, Ocular/physiology*
Visual Cortex/physiology*
Young Adult

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