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Published October 20, 2009 | Published + Supplemental Material
Journal Article Open

Color-tuned neurons are spatially clustered according to color preference within alert macaque posterior inferior temporal cortex


Large islands of extrastriate cortex that are enriched for color-tuned neurons have recently been described in alert macaque using a combination of functional magnetic resonance imaging (fMRI) and single-unit recording. These millimeter-sized islands, dubbed "globs," are scattered throughout the posterior inferior temporal cortex (PIT), a swath of brain anterior to area V3, including areas V4, PITd, and posterior TEO. We investigated the micro-organization of neurons within the globs. We used fMRI to identify the globs and then used MRI-guided microelectrodes to test the color properties of single glob cells. We used color stimuli that sample the CIELUV perceptual color space at regular intervals to test the color tuning of single units, and make two observations. First, color-tuned neurons of various color preferences were found within single globs. Second, adjacent glob cells tended to have the same color tuning, demonstrating that glob cells are clustered by color preference and suggesting that they are arranged in color columns. Neurons separated by 50 μm, measured parallel to the cortical sheet, had more similar color tuning than neurons separated by 100 μm, suggesting that the scale of the color columns is <100 μm. These results show that color-tuned neurons in PIT are organized by color preference on a finer scale than the scale of single globs. Moreover, the color preferences of neurons recorded sequentially along a given electrode penetration shifted gradually in many penetrations, suggesting that the color columns are arranged according to a chromotopic map reflecting perceptual color space.

Additional Information

© 2009 National Academy of Sciences. Edited by David H. Hubel, Harvard Medical School, Boston, MA, and approved August 21, 2009 (received for review October 29, 2008). Published online before print October 1, 2009. Author contributions: B.R.C. and D.Y.T. designed research; B.R.C. performed research; B.R.C. and D.Y.T. contributed new reagents/analytic tools; B.R.C. analyzed data; and B.R.C. wrote the paper. We thank Nicole Schweers and Sebastian Moeller for technical assistance and Margaret Livingstone, David Hubel, and Thorsten Hansen for comments on the manuscript. We also thank Anya Hurlbert for her expert advice on color spaces and MATLAB code. This work was funded by the Alexander von Humboldt Foundation, the German Ministry of Science (Grant 01GO0506, Bremen Center for Advanced Imaging), the Neuroscience Program, Wellesley College, and the Whitehall Foundation.

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Published - Conway2009p6207P_Natl_Acad_Sci_Usa.pdf

Supplemental Material - Conway2009p6207P_Natl_Acad_Sci_Usa_supp.pdf


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