Day 1, you give the patient a painful stimulus.

Some researchers believe that a person's genes may regulate the way his or her body processes painful stimuli.

For example, repetition of a painful stimulus may make one more responsive to a loud noise.

We know that when someone is expecting a painful stimulus they feel it more.

Perhaps focused behaviors help them to block out painful stimuli.

Combined with the alcohol, it had shut down her system to the point where she responded only to painful stimuli.

When the eyes will not open for anything - even painful stimulus.

When the patient extends his/her limb after feeling a painful stimulus.

Then they watched the same people suffering from a painful stimulus.

Patients with right hemisphere damage had reduced arousal response to painful stimuli.