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. Author manuscript; available in PMC: 2017 May 10.
Published in final edited form as: Lab Anim (NY). 2013 Aug;42(8):292–300. doi: 10.1038/laban.255

FIGURE 1.

FIGURE 1

Intracranial self-stimulation (ICSS) is an operant conditioning procedure that produces stable baseline behavioral response rates for research on pain-related behavioral depression. (a) A rat equipped with an intracranial electrode that targets the brain reward pathway. During experimental sessions, the rat is placed into an operant conditioning chamber, and the electrode is connected by a cable to a stimulator (not shown). Pressing a lever in the chamber illuminates a set of stimulus lights located over the lever and activates the stimulator to deliver pulses of brain stimulation via the electrode. Rats readily learn to press the lever for brain stimulation reinforcement. (b) Illustrative baseline ‘frequency-rate’ curve for ICSS response rates. ICSS response rate (normalized and expressed as a percentage of the maximum control rate, %MCR) increases with increases in the magnitude of brain stimulation reinforcement (expressed on a log scale as the frequency of electrical stimulation in Hz). Data adapted from ref. 31 and represent the mean ± s.e.m. of values from 34 rats.