Switching attention--additional aspects for the analysis

Problems related to attentional functions have often been reported within the neurotoxicology of long-term exposure to solvents, but knowledge about neuroanatomical sites involved in this degenerative process is still rare. However, some studies have emphasized the frontal cortex as a region of structural or functional changes in long-term exposed patients or accidental intoxications. Neurobehavioral tests using active switching tasks are widely used to detect frontal lobe dysfunction. Test batteries used in neurotoxicology provide such tasks but standard test interpretations often neglect these aspects. Rotogravure printing workers exclusively exposed to toluene were investigated in a longitudinal study with cross-sectional design. Data from two examination periods are presented. In the first sample 333 male workers were investigated. In the second examination period 278 workers could be retested. The workers differed with respect to level and duration of lifetime exposure to toluene. All subjects completed a neurobehavioral test battery including the task switching attention (EURONES). Different parameters were computed for consecutive trials with constant vs. shifted tasks and repetitions vs. changes of the response direction. In general the expected interaction between the two sequence factors could not be observed. In both examination periods the alternative strategy revealed no marked differences between task/response shifts. Considering the result of previous studies on task/response shifts, the results were highly unexpected. One explanation might be the strong deviations from equality for the relative frequencies of the four sequence conditions, resulting in biased expectancies. These may have superimposed on the basic effects of task shifts. However, in both examination periods weak effects of task shift could be revealed in the subgroup of the long-term exposed workers. In further studies it is necessary to balance conditions more carefully in order to exploit the sensitivity that the measurement of shift costs promises to provide. The exposure-related results of this study support this aspect.