Neural correlates of reversing illusory rotation or depth: an MEG study
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1
Center for Behavioral and Brain Sciences, Germany
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2
Leibniz Institute for Neurobiology, Germany
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3
Otto-von-Guericke Universität, Department of Neurology, Germany
A cloud of dots in planar motion can induce the compelling illusion of a rotation in depth (“structure-from-motion”). Surprisingly, reversing the planar motion does not necessarily reverse the global illusory rotation. In fact, two perceptual outcomes are possible: the illusory rotation either reverses (while illusory depth is maintained) or remains constant (while illusory depth is inverted) (Pastukhov, Vonau, & Braun, 2012). Importantly, the latter outcome leaves the overall illusory shape unchanged (provided it is rotationally symmetric, e.g., a sphere, or cylinder), as only the local illusory depth of individual dots is affected.
Here we compare EEG/MEG activity associated with these alternative perceptual interpretations of physically identical events (reversals of planar motion): Eighteen observers viewed an ambiguously rotating sphere presented for 1500 ms with a reversal of planar motion occurring with at variable points in time. Observers reported whether the global illusory rotation had reversed (maintaining local illusory depth) or had remained constant (inverting local illusory depth). To ensure that both outcomes were equally probable, we adjusted the distance between opposing dots at the moment of reverals (Stonkute, Braun, & Pastukhov, 2012).
Reversals of global illusory rotation were associated with phasic activity in a medial-temporal area (presumptive hMT, ~180 ms) and, somewhat later, in an immediately adjacent superior region (~270 ms). In contrast, reversals of local illusory depth elicit phasic activity near the intraparietal sulcus (presumptive LIP) and in ventral extrastriate areas (~215 ms). The latter activity pattern is likely to reflect renewed “binding” between neural representations of local depth and of global rotation.
References
Pastukhov, A., Vonau, V., & Braun, J. (2012). Believable change: Bistable reversals are governed by physical plausibility. Journal of vision, 12(1), 17.
Stonkute, S., Braun, J., & Pastukhov, A. (in press). The role of attention in ambiguous reversals of structure-from-motion. PLoS ONE.
Keywords:
depth,
EEG,
feature binding,
MEG,
motion,
multi-stable displays,
structure-from-motion
Conference:
Bernstein Conference 2012, Munich, Germany, 12 Sep - 14 Sep, 2012.
Presentation Type:
Poster
Topic:
Sensory processing and perception
Citation:
Pastukhov
A,
Bartsch
M,
Stonkute
S,
Hopf
M and
Braun
J
(2012). Neural correlates of reversing illusory rotation or depth: an MEG study.
Front. Comput. Neurosci.
Conference Abstract:
Bernstein Conference 2012.
doi: 10.3389/conf.fncom.2012.55.00231
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Received:
11 May 2012;
Published Online:
12 Sep 2012.
*
Correspondence:
Dr. Alexander Pastukhov, Center for Behavioral and Brain Sciences, Magdeburg, Germany, pastukhov.alexander@gmail.com