ERPs and behavioural indices of long-term preattentive and attentive deficits after closed head injury.

Attentional deficits are often reported even years after sustaining a closed head injury (CHI). Disturbance of cognitive attentional functions following CHI has been documented in both behavioural and event-related brain potential (ERP) studies. Recently, the possibility that the sequelae of CHI extend to preattentive processes of attention has been pointed out. We used a paradigm that makes it possible to assess simultaneously the processing of relevant information and involuntary mechanisms of attention to gain further insight in this matter. Eleven patients with CHI greater than 1 year post-trauma and 14 age-matched control subjects were engaged in the performance of a continuous visual reaction time (RT) discrimination task while ignoring streams of auditory task-irrelevant stimuli. The main characteristic in the paradigm was that all visual stimuli were shortly preceded by an auditory stimulus, which could be a repeated (90%) or a different (deviant) tone. We measured performance on the discrimination task, and ERP indices of preattentive (mismatch negativity MMN) and attentive information processing (P1, N165, P3b). In relation to control subjects, CHI patients showed an attenuation of the MMN evoked by the deviant-tone. In response to the visual stimuli, CHI patients showed a delay of P1, and a reduction of the N165 and P3b components. Moreover, they had slower RT and missed more responses in a visual discrimination task. These results indicate both preattentive and attentive deficits, which is consistent with the typical diffuse axonal injury (DAI) resulting after CHI.