Role of sensory modality and motor planning in the slowing of patients with traumatic brain injury: a meta-analysis.

Here we present a meta-analysis of studies that examined the reaction times (RT) of patients with traumatic brain injury (TBI) on decision tasks carried out under time pressure. To detect the presence of global components in the data describing the slowing of TBI patients, we used predictions of the difference engine model (DEM). According to this model, performance can be understood by referring to two separate and independent compartments, one cognitive and one sensory-motor. Results confirm previous observations that TBI patients are delayed with respect to matched controls by a multiplicative factor affecting performance over and above the specific characteristics of the tasks. This meta-analysis also shows that the global factor affecting TBI patients' performance is selective for the visual modality. No over-additivity was detected on tasks in the acoustic modality. Estimates of the time taken by the sensory-motor component of the task indicated substantial slowing in the TBI patients. This delay was particularly marked in patients with severe TBI.