Abstract
Background. Persistent deficits in cognitive control have been documented following traumatic brain injury (TBI) but are inconsistently related to the presence and location of focal lesions.
Objective. Functional magnetic resonance imaging (fMRI) was used to examine brain activation during a cognitive control task in patients with moderate to severe TBI or orthopedic injury (OI).
Methods. Fourteen TBI patients and 10 OI patients underwent fMRI at 3 months postinjury using a stimulus-response compatibility task in which response accuracy and reaction time were measured. Performance between the groups was equated by individually adjusting the amount of training. Groups did not differ in age, gender, or education.
Results. Brain activation during stimulus-response incompatibility was greater in TBI patients than in OI patients within the cingulate, medial frontal, middle frontal, and superior frontal gyri. However, the positive regression of activation with response accuracy during stimulus-response incompatibility indicated a stronger relationship for OI patients than the TBI group within the anterior cingulate gyrus, medial frontal, and parietal regions, as well as deep brain structures (eg, brainstem). The number of focal lesions within either the whole brain or within prefrontal areas was not related to brain activation, but there was a relationship between activation and TBI severity.
Conclusions. These findings suggest that neural networks mediating cognitive control are altered after moderate to severe TBI, possibly as a result of diffuse axonal injury, and that the typical relationship of brain activation to performance is disrupted.