Figure 1. Task Schematic.
A. Simplified schematic for Cued Response Inhibition Task. At the beginning of each trial, two cues are presented simultaneously: lighting of the response port, and a tone. The tone informs subjects to withhold a response into the lit port; responses during the tone are scored as failed trials and cause entry to the ITI. The tone lasts for 5, 10, 20, or 30 seconds (lengths determined pseudo-randomly). After termination of the tone, the port remains lit for 5 seconds. During this window, responses are rewarded. Critical measures of interest are: response inhibition ratio (correct: incorrect responses), latency to respond after tone termination, and omitted trials. B. After training, rats were given an 8-day methylphenidate injection schedule. Doses of .3, 1.0, 3.0 mg/kg methylphenidate or saline vehicle were administered on days 1, 3, 5, and 7, with drug-free sessions in between to allow washout and establish a consistent baseline.
