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This Article Full Text Full Text (PDF) All Versions of this Article: 577/3/805    most recent jphysiol.2006.120071v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Niu, Y.-Q. Articles by Wang, S.-R. Search for Related Content PubMed PubMed Citation Articles by Niu, Y.-Q. Articles by Wang, S.-R. Related Collections Neuroscience

¹ Laboratory for Visual Information Processing, State Key Laboratory of Brain and Cognitive Sciences, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, P. R. China

Misinterpretations of visual information received by the retina are called visual illusions, which are known to occur in higher brain areas. However, whether they would be also processed in lower brain structures remains unknown, and how to explain the neuronal mechanisms underlying the motion after-effect is intensely debated. We show by extracellular recording that all motion-sensitive neurons in the pigeon's pretectum respond similarly to real and illusory contours, and their preferred directions are identical for both contours in unidirectional cells, whereas these directions are changed by 90 deg for real versus illusory contours in bidirectional cells. On the other hand, some pretectal neurons produce inhibitory (excitatory) after-responses to cessation of prolonged motion in the preferred (null) directions, whose time course is similar to that of the motion after-effect reported by humans. Because excitatory and inhibitory receptive fields of a pretectal cell overlap in visual space and possess opposite directionalities, after-responses to cessation of prolonged motion in one direction may create illusory motion in the opposite direction. It appears that illusory contours and motion could be detected at the earliest stage of central information processing and processed in bottom-up streams, and that the motion after-effect may result from functional interactions of excitatory and inhibitory receptive fields with opposite directionalities.

(Received 28 August 2006; accepted after revision 6 October 2006; first published online 12 October 2006)
Corresponding author S.-R. Wang: Laboratory for Visual Information Processing, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, P. R. China. Email: wangsr{at}sun5.ibp.ac.cn