Cognitive deficits after traumatic coma.

Survivors from a coma due to severe traumatic brain injury (TBI) frequently suffer from long-lasting disability, which is mainly related to cognitive deficits. Such deficits include slowed information processing, deficits of learning and memory, of attention, of working memory, and of executive functions, associated with behavioral and personality modifications. This review presents a survey of the main neuropsychological studies of patients with remote severe TBI, with special emphasis on recent studies on working memory, divided attention (dual-task processing), and mental fatigue. These studies found that patients have difficulties in dealing with two simultaneous tasks, or with tasks requiring both storage and processing of information, at least if these tasks require some degree of controlled processing (i.e., if they cannot be carried out automatically). However, strategic aspects of attention (such as allocation of attentional resources, task switching) seem to be relatively well preserved. These data suggest that severe TBI is associated with a reduction of resources within the central executive of working memory. Working memory limitations are probably related to impaired (i.e., disorganized and augmented) activation of brain executive networks, due to diffuse axonal injury. These deficits have disabling consequences in everyday life.