Analysis of the electroencephalographic activity during the Necker cube reversals by means of the wavelet transform

Abstract

In previous studies, a perceptual switching related potential was obtained during the observation of a multistable dynamic reversal pattern, where the averaging of the single responses was triggered by subjects pressing a button. The present methodological study aims to increase the signal quality of perceptual switching related potentials considering the dependence of the measurement method on the reaction time of the subject, which may vary significantly during a session, leading to low-amplitude waveform in the averaged event-related-potential (ERP). To overcome this problem in measuring the electrophysiological correlate of an internal event, a pattern selection method based on the wavelet transform (WT) is proposed to choose a subset of single ERPs with more homogenous latencies. Nine subjects observed a Necker cube and were instructed to press the button immediately after perceptual switching. A slow, low-amplitude positive wave with frontocentral amplitude maxima was observed around 250 ms prior to the button press. After the application of a 5 octave WT on single sweeps, the time-frequency coefficients obtained in each octave were averaged across trials. The most dominant feature representing the averaged ERP was the delta (0.5-4 Hz) coefficient occurring between 250 and 125 ms before the button press. By averaging the subset of the single sweeps containing this property, a sharpening and significant amplitude increase of the response peak was observed.

Theta response in schizophrenia is indifferent to perceptual illusion

“…A reversal-related delta component, by its functional and topographical similarity to the P300, was interpreted as reflecting the recognition of the perceptual change (BasarEroglu, et al, 1993;Isoglu-Alkac et al, 1998;Mathes, Strüber, Stadler, & Basar-Eroglu, 2006;Strüber & Herrmann, 2002). Top-down processing during multistable perception is indicated by the frontal maximum of theta Nakatani & van Leeuwen, 2005) and gamma activity (Basar-Eroglu, Strüber, Kruse, et al, 1996;Strüber, et al, 2000;Strüber, et al, 2001).…”

Necker cube reversals during long-term EEG recordings: Sub-bands of alpha activity

“…In this context, the timing of the involved neural mechanisms is of special importance, which can be analyzed by means of EEG or MEG providing high temporal resolution. Previous ERP studies on multistable perception found a late P300-like component induced by the figure reversal (O'Donnell et al, 1988;Basar-Eroglu et al, 1993;Isoglu-Alkac et al, 1998Strü ber et al, 2001;Strü ber and Herrmann, 2002), which indicates the conscious 0167-8760/$ -see front matter D 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.ijpsycho.2005.05.002 recognition of perceptual change and, therefore, the closure of the reversal process.…”

Poster Presentations

“…These findings may help to explain previous contradictory results of respiration effects on RT and may guide future research on cognitive enhancement strategies. In our recent studies (Isoglu-Alkac et al, 1998, we have shown the gradual decrease of alpha activity, as well as increased delta and gamma activity during Necker-Cube reversals. We suggested that gamma activity plays a role in attentional top -down processing, whereas desynchronized alpha might be related to bottom -up processes.…”

“…The 40-Hz recordings were collected to provide additional information to that obtained by Bertrand et al (1990), Butler et al (1996, 1998), Fisher et al (1996 and Guérit et al (1998) who monitored coma states and recorded evoked potentials (EP) in patients with prolonged coma. Fischer et al (1999), showed that their late cortical recordings differed from healthy subjects in terms of waveform, latencies and amplitudes.…”