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° 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.