Traumatic brain injury and attention : postconcussion symptoms and indices of reaction time

Abstract

One of the consequences of traumatic brain injury is the postconcussion syndrome. The symptoms in this syndrome include headache, dizziness, poor memory, poor concentration, easy fatigue, drowsiness, irritability, sensitivity to light, sensitivity to noise, low alcohol tolerance, visual problems, auditory problems, nausea, vomiting, anxiety, and depression. Several factor analytic studies have shown that these symptoms load onto cognitive and noncognitive factors (Bohnen, Twijnstra, & Jolles, 1992). The aim of this study was to determine whether patients who report different symptoms also evidence differences in cognitive deficits, as indexed by reaction time. For this purpose 106 subjects (mean age 25.92 years; SD=6.05) of both sexes were tested on 8 reaction time tasks adapted from Shum, McFarland, Bain, and Humphreys (1990). There were 54 traumatic brain injury patients (mean age 26.40 years; SD=6.23) drawn from three Pretoria hospitals. They were

heterogeneous with respect to diagnosis and severity of injury. For the controls

(N=52), the mean age was 25.43 years (SD=5.88). The eight reaction time tasks constituted 4 task variables, each with 21evels. From these tasks, 36 reaction time indexes were derived. The indexes were classified into 4 groups, viz., reaction time (RT), movement time (MT), total reaction time (TT), and subtraction scores

(SB, the difference between the 2 levels for each task variable).

RT reflects the decision component and MT reflects the response execution component of reaction time. Partial correlation coefficients for all symptoms (p0,01) showed that some symptoms were most frequently associated with RT whilst others were most frequently associated with MT. On factor analysis with varimax rotation, symptoms loaded predominantly with SB scores. Symptoms also loaded with different task variablseuiggesting that they correlated with deficits on

different stages of information processing. Taking into account possible methodological constraints that were discussed, these results confirm that different symptoms within the postconcussion syndrome correlate with different cognitive deficits. The correlations between symptoms and indices of reaction time are moderated by the characteristics of the symptoms (frequency & intensity), and the duration since injury. These findings have significance for understanding the aetiology of the postconcussion symptoms and for planning treatment.