Objective
To evaluate the effect of methylphenidate on cognitive function especially on working memory and visuospatial attention in the patients with traumatic brain injury (TBI).

Method
Eighteen subjects, 16 males and 2 females, with TBI were enrolled. Their mean age was 34.2 years old. A double-blind placebo-controlled study was designed. The baseline cognitive assessment was performed before the administration of drug. Two days after the baseline study, 20 mg of methylphenidate or placebo was administered. The second cognitive assessment was performed 2 hours after the treatment. The follow-up assessment conducted two days after the second test. Cognitive assessments consisted of 'one-back working memory task' and 'endogenous visuospatial attention task', designed using SuperLab Pro 2.0^Ⱂ software.

Results
In one-back working memory test, there was significant improvement of response accuracy in methylphenidate group in comparison with placebo group (p＜0.01). Significant shortening of reaction time was also seen after the administration of drug in methylphenidate group (p＜0.05). In endogenous visuospatial attention test, significant improvement of response accuracy was noticed after the administration of drug in methylphenidate group (p＜0.05).

Conclusion
These results demonstrated that the administration of methylphenidate was beneficial in improving cognitive function following TBI. The effect was prominent in the accuracy of working memory.