Biochemistry. In the article "Clonal selection and in vivo quantitation of protein interactions with protein-fragment complementation assays" by Ingrid Remy and Stephen W. Michnick, which appeared in number 10, May 11, 1999, of Proc. Natl. Acad. Sci. USA (96, 5394-5399) Immunology. In the article entitled "Murine natural killer cells contribute to the granulomatous reaction caused by mycobacterial cell walls" by I. Apostolou, Y. Takahama, C. Belmant, T. Kawano, M. Huerre, G. Marchal, J. Cui, M. Taniguchi, H. Nakauchi, J.-J. Fournié, P. Kourilsky, and G. Gachelin, which appeared in number 9, April 27, 1999 of Proc. Natl. Acad. Sci. USA (96,(5141)(5142)(5143)(5144)(5145)(5146), the authors request that the following correction be noted: the title should be "Murine natural killer T (NKT) cells contribute to the granulomatous reaction caused by mycobacterial cell walls." Neurobiology. In the articles "An empirical basis for Mach bands" by R. Beau Lotto, S. Mark Williams, and Dale Purves, which appeared in number 9, April 27, 1999, of Proc. Natl. Acad. Sci. USA (96,(5239)(5240)(5241)(5242)(5243)(5244), and "Mach bands as empirically derived associations" by R. Beau Lotto, S. Mark Williams, and Dale Purves, which appeared in number 9, April 27, 1999, of Proc. Natl. Acad. Sci. USA (96,(5245)(5246)(5247)(5248)(5249)(5250), the following correction should be noted. The reproduction of some of the figures in these papers was unsatisfactory due to the presence of moiré patterns and other deficiencies in the published versions. Given the difficulty in faithfully reproducing gradients in print, readers may wish to view the electronic versions of the figures at purveslab.neuro.duke.edu.Psychology. In the article "Spatial attention affects brain activity in human primary visual cortex" by Sunil P. Gandhi, David J. Heeger, and Geoffrey M. Boynton, which appeared in number 6, March 16, 1999, of Proc. Natl. Acad. Sci. USA (96, 3314-3319), due to an error in the PNAS office, a sentence was omitted. The sentence is shown in bold type in context in the complete paragraph below.On the other hand, it is certainly possible that the V1 modulation we observed might have nothing to do with the improved behavioral performance. For example, the memory load differs between the tasks in the main experiment and the spatial uncertainty experiment. In the spatial uncertainty experiment, subjects must remember two speeds instead of one during the 250 msec inter-stimulus interval. This difference in memory load might be causing the improved behavioral performance. Or the improved performance may result from subjects simply ignoring information from the uncued side, and thus may not be causally related to V1 modulation. It is difficult, however, to imagine that such a significant modulation of activity in visual cortex would fail to have consequences on perceptual thresholds.
7610Corrections Proc. Natl. Acad. Sci. USA 96 (1999) Communicated by Jacob Nachmias, University of Pennsylvania, Philadelphia, PA, December 21, 1998 (received for review...