Indices of slowness of information processing in head injury patients: Tests for selective attention related to ERP latencies

We explored the relation between neuropsychological (attention tests involving time constraints) and neurophysiological (N2 and P3 event-related potential (ERP) latencies) indices of slowness of information processing after closed head injury (CHI). A group of 44 CHI patients performed worse than healthy controls on most neuropsychological indices, and had significantly longer ERP latencies. Significant correlations between neuropsychological measures and ERP latencies were found only for the 3 subtasks of the Stroop test. In additional multiple regression analyses P3 latency appeared the best predictor in Stroop Color only. A possible explanation is that stimulus evaluation processes comprise a relatively large part of performance on this subtask. In Stroop Color-Word, response related processes are supposed to play a greater role, reducing the role of the preceding input related processes. The absence of significant correlations between P3 latency and scores on the other attention tests suggests a relatively small role of stimulus evaluation processes in these tasks, implying that these tasks are not sensitive to slowness of these processes. The Stroop test appears to be the only attention test administered in which slowness in stimulus evaluation processes requiring selective attention contributes significantly to the delay in final performance on the task