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.
