Evoked potential correlates of posttraumatic amnesia after closed head injury.

The P-300 component of evoked potentials to a rare tone was measured in normal volunteers and in patients with closed head injuries who either were confused (in posttraumatic amnesia) or had recovered from posttraumatic amnesia and were oriented at the time of recording. The latency of this component, which reflects cortical processing of stimuli, varied reliably, with the degree of orientation being longest for confused patients and shortest for normal subjects. On the basis of these data, we suggest that the P-300 latency can be used as a physiological index of cognitive function in patients with closed head injury.