Nearly instantaneous brightness induction.
Brightness induction is the modulation of the perceived intensity of a region by the luminance of surrounding regions and reveals fundamental properties of neural organization in the visual system. Grating induction affords a unique opportunity to precisely measure the temporal properties of induction using a quadrature motion technique. Contrary to previous reports that induction is a sluggish process with temporal frequency cutoffs of 2-5 Hz (R. L. DeValois, M. A. Webster, K. K. DeValois, & B. Lingelbach, 1986; A. F. Rossi & M. A. Paradiso, 1996), we find that induction is nearly instantaneous. The temporal response of induced brightness differs from that of luminance gratings by a small time lag (<1 ms), or by a small temporal phase lag (<0.016 cycle), and remains relatively constant across wide variations in test field height. These data are not easily explained by an edge-dependent, homogeneous filling-in process (A. F. Rossi & M. A. Paradiso, 1996); however, they are consistent with an explanation of brightness induction based on spatial filtering by cortical simple cells (B. Blakeslee & M. E. McCourt, 1999).
Blakeslee
Barbara
B
Center for Visual Neuroscience, Department of Psychology, North Dakota State University, Fargo, ND 58105-5075, USA. Barbara.blakeslee@ndsu.edu
McCourt
Mark E
ME
D015350:Contrast Sensitivity / Q000502:physiology*; D006801:Humans; D008027:Light; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010775:Photic Stimulation