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.
Rotating-half-circle stimulus. The half circle rotates about the fixation point periodically. The first and fifth panels represent the beginning of the first and second cycle. The half circle is filled with flickering checks to optimize V1 response.
