Figure 3: The figure summarizes (N=8) the effect of acute and chronic effect of 2.5 mg/kg methylphenidate (MPD) on Horizontal activity, Total Distance Traveling, and number of stereotypic movement. The black circle sums the activity/ 10 min after the initial (acute) MPD injections, the white circle sums the activity at experimental day 11 after six daily MPD exposure and 3 washout days. The histogram in the upper right corner depicts the total change from two baseline days activity (set arbitrarily at 0) and six daily MPD exposure, 5 days of washout and MPD rechallenge at day 14. The numbers indicate the experimental days. * indicates significant (p<0.05) from the initial effect of MPD. The figure shows that repetitive (chronic) MPD elicited behavioral sensitization.