RESUMO
Stimulants decrease reaction time in humans as well as laboratory rats. This effect is seen as a decrease in average reaction time or a shift in the distribution peak towards shorter reaction times. However, response-time distributions are typically skewed, exhibiting a positive tail. Our goal for this project was to develop a method of analyzing reaction-time distributions in the rat which will allow us to study systematically measures of central tendency and distribution skew. This analysis subdivided reaction time into initiation time and movement time, and also subdivided the response time distributions into distribution mode and distribution skew. Rats were trained on a two-choice visual reaction-time task. We then evaluated the effects of stimulus salience and methamphetamine (METH) treatment (vehicle, 0.25, 0.5, 1.0, and 1.5 mg/kg) on measures of distribution mode and skew. Stimulus salience decreased initiation time mode, initiation time skew and movement time skew, but had no effect on movement time mode. METH had a greater effect on skew for the initiation time distribution and a greater effect on mode for the movement time distribution. This analysis will serve as a useful method of determining whether initiation time and movement time, as well as distribution mode and distribution skew, represent different behavioral processes in the rat.
