Dissociation of motor and cognitive processes in multistable perception
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1
Brain research Lab, University of Vienna, Austria
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2
Institute for Psychology and Cognition Research, University of Bremen, Germany
Multistable visual perception refers to phenomena, in which one invariant stimulus pattern is perceived in at least two different, mutually exclusive ways. Thus, such stimuli offer unique insights into the organization of visual perception, as well as the mechanisms that integrate stimulus-driven (bottom up) and attention-driven (top down) aspects of information processing (1). Previous work from our group has shown the occurrence of a positive delta-component starting about 200ms before perceptual reversals (2, 3). However, as subjects had to press a button in order to indicate reversals, a possible overlap with motor-related potentials could not be ruled out.The aim of the current study was to dissociate the time point of the perceptual reversal from the button press, in order to investigate the reversal-related components independently from motor activity. The stimulus used was the so called stroboscopic alternative motion (SAM). This dynamic multistable pattern consists of two diagonal pairs of black dots flashing up alternately, which results in the perception of an either horizontal or vertical movement. Subjects were instructed to press a button whenever a perceptual reversion occurred. In addition to the ‘standard’ condition, where the response should be made immediately after reversals, we introduced a ‘dissociated’ condition, in which subjects were asked to delay their response for a period of 4 movement-cycles of the SAM. As every cycle takes 250 ms to complete, this procedure separates the perceptual reversal from the motor-response by 1000ms. 20 students (12 female, mean age 23 years) participated in the study. EEG was continuously recorded with 16 electrodes from frontal, central, parietal and occipital sites. Epochs from -3000 ms to 1000 ms around the button press were extracted from the continuous EEG data, and epochs containing eye and muscle artifacts were eliminated. 7 subjects had to be excluded from the dataset due to corrupt data or an insufficient number of epochs (less than 20). For statistical analysis, mean power in the delta frequency band over all subjects was computed for the following time windows: 2000ms to 1500ms before button press; 750ms before the button press lasting until 250ms after the button press. Consequently, delta power within those time windows was compared between the ‘standard’ and the ‘dissociated’ condition. The results strongly suggest that the reversal-related positivity observed so far is a stable electrophysiological correlate of perceptual reversions, and independent of overlapping motor processes.
References
1. 1. Leopold D.A. & Logothestis N.K. (1999), Trends Cognit.Sci.,3, 254-264.
2. 2. Basar- Eroglu C., Strüber D., Stadler M., Kruse P., Basar E. (1993), Int.J.Neurosci., 37, 139-159.
3. 3. Mathes M., Strüber D., Stadler M., Basar-Eroglu C. (2006), Neurosci. Lett, 145-149.
Conference:
10th International Conference on Cognitive Neuroscience, Bodrum, Türkiye, 1 Sep - 5 Sep, 2008.
Presentation Type:
Poster Presentation
Topic:
Brain Electrical Oscillations in Cognition
Citation:
Pomper
U,
Mathes
B,
Walla
P and
Basar-Eroglu
C
(2008). Dissociation of motor and cognitive processes in multistable perception.
Conference Abstract:
10th International Conference on Cognitive Neuroscience.
doi: 10.3389/conf.neuro.09.2009.01.134
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Received:
05 Dec 2008;
Published Online:
05 Dec 2008.
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Correspondence:
Ulrich Pomper, Brain research Lab, University of Vienna, Vienna, Austria, ulrich.pomper@univie.ac.at