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The Journal of Neuroscience, February 28, 2007, 27(9):2186-2195; doi:10.1523/JNEUROSCI.4173-06.2007

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Behavioral/Systems/Cognitive
Orientation-Selective Adaptation to Illusory Contours in Human Visual Cortex

Leila Montaser-Kouhsari,¹ Michael S. Landy,^1,2 David J. Heeger,^1,2 and Jonas Larsson^1,2

¹Department of Psychology and ²Center for Neural Science, New York University, New York, New York 10003

Correspondence should be addressed to Leila Montaser-Kouhsari, Department of Psychology, New York University, 6 Washington Place, Room 957, New York, NY 10003. Email: lmk306{at}nyu.edu

Humans can perceive illusory or subjective contours in the absence of any real physical boundaries. We used an adaptation protocol to look for orientation-selective neural responses to illusory contours defined by phase-shifted abutting line gratings in the human visual cortex. We measured functional magnetic resonance imaging (fMRI) responses to illusory-contour test stimuli after adapting to an illusory-contour adapter stimulus that was oriented parallel or orthogonal to the test stimulus. We found orientation-selective adaptation to illusory contours in early (V1 and V2) and higher-tier visual areas (V3, hV4, VO1, V3A/B, V7, LO1, and LO2). That is, fMRI responses were smaller for test stimuli parallel to the adapter than for test stimuli orthogonal to the adapter. In two control experiments using spatially jittered and phase-randomized stimuli, we demonstrated that this adaptation was not just in response to differences in the distribution of spectral power in the stimuli. Orientation-selective adaptation to illusory contours increased from early to higher-tier visual areas. Thus, both early and higher-tier visual areas contain neurons selective for the orientation of this type of illusory contour.

Key words: illusory contours; adaptation; orientation selectivity; fMRI; visual cortex; spatial vision

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Received Sept. 22, 2006; revised Jan. 16, 2006; accepted Jan. 17, 2007.

Correspondence should be addressed to Leila Montaser-Kouhsari, Department of Psychology, New York University, 6 Washington Place, Room 957, New York, NY 10003. Email: lmk306{at}nyu.edu

Related articles in J. Neurosci.:

Seeing Things: Illusory Contours in the Human Visual Brain

Sarah Weigelt
J. Neurosci. 2007 27: 5269-5270. [Full Text]  

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				M. S. Tibber, D. R. Melmoth, and M. J. Morgan Biases and Sensitivities in the Poggendorff Effect when Driven by Subjective Contours Invest. Ophthalmol. Vis. Sci., January 1, 2008; 49(1): 474 - 478. [Abstract] [Full Text] [PDF]

				S. Weigelt Seeing Things: Illusory Contours in the Human Visual Brain J. Neurosci., May 16, 2007; 27(20): 5269 - 5270. [Full Text] [PDF]

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