Effects of two doses of methylphenidate on verbal information processing in hyperactive children

Nine hyperactive children participated in three sessions. During each they were given one of three drugs (placebo, 10 mg, or 21 mg of methylphenidate) in a double-blind crossover study. Following drug administration they were tested on three cognitive tasks. For one task, structural, acoustic, or semantic degrees of encoding of verbal information were induced. Memory for the verbal information was then tested. The 10-mg dose resulted in overall improvement of word recognition and recall. The 21-mg dose did not result in improvement. Amount of improvement was not related to degree of encoding of words. Two other tasks, learning a list of words and visual search of letters from a briefly presented display, were not affected by either the 10- or 21-mg dose. The results indicate that verbal learning can be facilitated by a low dose of methylphenidate but that the dose range may be narrow. Also, certain individuals did not respond favorably to either dose. In discussing the results, the possibility is presented that methylphenidate-induced facilitation may be restricted to certain types of learning or certain methods of assessing retrieval of information.