ERP indices of resource allocation difficulties in mild head injury

This study examined the hypothesis that distractibility is a characteristic sequela of mild closed head injury (MHI). The Minnesota Multiphasic Person ality Inventory (MMPI-2) was used to study whether comorbid stress-related symptoms are associated with behavioral and electrophysiological indexes of attention. Event-related potentials (ERPs) and performance (reaction time, accuracy) were studied in patients with MHI (n = 20), patients with fronta l lesions (n = 14), and healthy controls (n = 20) during a three-tone oddba ll task. Participants were instructed to detect rare target (2000 Hz) tones , and to withhold responding to equally rare distracter (500 Hz) tones and frequently occurring standard (1000 Hz) tones. All groups distinguished the two classes of deviants as indicated by the larger P3 amplitude to target relative to distracter tones. This indicates that the group with MHI was ca pable of differential allocation of attentional resources to target and non -target events. However, impaired performance and attenuated ERP amplitudes to both classes of deviants relative to patients with frontal lesions and controls, suggest limited availability, or expenditure of the resources nee ded for adequate task performance. In the group with MHI, both P3 amplitude acid reaction time (RT) were significantly related to subjectively reporte d distress. The difference in RT disappeared, whereas the P3 amplitude diff erences between the patient groups remained when adjusting for level of dis tress.