Complex sentence: Therapeutic doses of psychostimulants, like amphetamine and methylphenidate, improve performance on working memory tests both in normal functioning individuals and those with ADHD; moreover, these stimulants also act on general levels of arousal and, within the nucleus accumbens, improve task saliency.
Split into simpler sentences: Therapeutic doses of psychostimulants, like amphetamine and methylphenidate, improve performance on working memory tests both in normal functioning individuals and those with ADHD. Moreover, these stimulants also act on general levels of arousal and, within the nucleus accumbens, improve task saliency.