Decoding of coherent but not incoherent motion signals in early dorsal visual cortex

http://www.sciencedirect.com/science/article/pii/S1053811910004052#bb0190

 

NeuroImage
Volume 56, Issue 2, 15 May 2011, Pages 688-698
Multivariate Decoding and Brain Reading

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doi:10.1016/j.neuroimage.2010.04.011 | How to Cite or Link Using DOI

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Decoding of coherent but not incoherent motion signals in early dorsal visual cortex

Sponsored Article

Dietrich Samuel Schwarzkopf^a, b, , , Philipp Sterzer^c, 3 and Geraint Rees^{a, b, 1, 2}

^a UCL Institute of Cognitive Neuroscience, 17 Queen Square, London WC1N 3AR, UK

^b Wellcome Trust Centre for Neuroimaging at UCL, 12 Queen Square, London WC1N 3BG, UK

^c Department of Psychiatry, Charité Campus Mitte, Charitéplatz 1, D-10117 Berlin, Germany

Available online 10 April 2010. 

 

Abstract

When several scattered grating elements are arranged in such a way that their directions of motion are consistent with a common path, observers perceive them as belonging to a globally coherent moving object. Here we investigated how this coherence changes the representation of motion signals in human visual cortex using functional magnetic resonance imaging (fMRI) and multivariate voxel pattern decoding, which have the potential to reveal how well a stimulus is encoded in different contexts. Only during globally coherent motion was it possible to reliably distinguish fMRI signals evoked by different directions of motion in early visual cortex. This effect was specific to the retinotopic representation of the visual field quadrant in V1 traversed by the coherent element path and could not simply be attributed to a general increase in signal strength. Decoding was more reliable for cortical areas corresponding to the lower visual field. Because some previous studies observed poorer speed discrimination when motion was grouped, we also conducted behavioural experiments to investigate this with our stimuli, but did not reveal a consistent relationship between coherence and perceived speed. Taken together, these data show that neuronal populations in early visual cortex represent information that could be used for interpreting motion signals as unified objects.