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.
The upper image shows a needle covered by a black protector cap placed next to the hand (non-painful control stimulus). The lower image shows the (painful) injection of the same needle into the hand.
