Methylphenidate effect on hemispheric attentional imbalance in patients with traumatic brain injury: A psychophysical study

Primary objective: We found spatially asymmetric allocation of attention in patients with traumatic brain injury ( TBI) without overt asymmetry on neurological examination. The possible effect of Methylphenidate in reducing this asymmetry is evaluated in the current research. Research design: Psychophysical study using a visual spatial attention task. Identification rates were measured after precuing attention to different visual field loci. TBI patients were tested before, during and after administration of Methylphenidate. Methods and procedures: After precuing to a locus 5 degrees into the left or right hemifield, target patterns were presented briefly at the cued location ( valid), or on the opposite side ( invalid) - requiring an attentional shift. Patients were treated with a gradually increasing dosage of a psychostimulant over two weeks, followed by a similar two-week period of gradually diminishing dosage. Patients were tested before treatment, at its peak, and ( twice) following its completion. Main outcome and results: Patients demonstrated significantly worse performance with leftward than with rightward cross-hemifield shifts of attention. This difference was significantly reduced during and following treatment. Conclusions: Asymmetric performance and improvement with treatment suggest that diffuse TBI damage leads to a lateralized attention-related deficit. These findings support the hypotheses that attention is a distributed and asymmetrically lateralized function. The findings are consistent with the conclusion that Methylphenidate may be an effective treatment for attentional deficits in TBI patients.