A functional MRI study of multimodal selective attention following mild traumatic brain injury.

Previous work suggests that the ability to selectively attend to and resolve conflicting information may be the most enduring cognitive deficit following mild traumatic brain injury (mTBI). The current study used fMRI to evaluate potential differences in hemodynamic activation in 22 mTBI patients and 22 carefully matched healthy controls (HC) during a multimodal selective attention task (numeric Stroop). Behavioral data indicated faster reaction times for congruent versus incongruent trials and for stimuli presented at 0.66 compared to 0.33 Hz across both groups, with minimal differences in behavioral performance across the groups. Similarly, there were no group-wise differences in functional activation within lateral and medial prefrontal cortex during the execution of cognitive control (incongruent versus congruent trials). In contrast, within-group comparisons indicated robust patterns of attention-related modulations (ARM) within the bilateral dorsolateral prefrontal cortex and bilateral visual streams for HC but not mTBI patients. In addition, mTBI patients failed to exhibit task-induced deactivation within the default-mode network (DMN) under conditions of higher attentional load. In summary, in spite of near normal behavioral performance, current results suggest within-group abnormalities during both the top-down allocation of visual attention and in regulating the DMN during the semi-acute stage of mTBI.