Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Visual stimuli generated either by choosing random intensity values for each pixel (Panel A) or by choosing intensity values semi-randomly, taking into account basic statistical properties of the amplitude spectrum of natural images (Panel B).
