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.
Masking conditions are presented here in a viewport measuring 90 by 90 deg. of field of view, mask radii are proportionally accurate. From left to right: control no-mask condition, central mask of six deg. of radius, peripheral mask of six deg. of radius.
