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Three experiments investigated whether spatial and nonspatial components of visual attention would be influenced by changes in (healthy, young) subjects' level of alertness and whether such effects on separable components would occur independently of each other. The experiments used a no-cue/alerting-cue design with varying cue-target stimulus onset asynchronies in two different whole-report paradigms based on Bundesen's (1990) theory of visual attention, which permits spatial and nonspatial components of selective attention to be assessed independently. The results revealed the level of alertness to affect both the spatial distribution of attentional weighting and processing speed, but not visual short-term memory capacity, with the effect on processing speed preceding that on the spatial distribution of attentional weighting. This pattern indicates that the level of alertness influences both spatial and nonspatial component mechanisms of visual attention and that these two effects develop independently of each other; moreover, it suggests that intrinsic and phasic alertness effects involve the same processing route, on which spatial and nonspatial mechanisms are mediated by independent processing systems that are activated, due to increased alertness, in temporal succession.

In the present study, the authors investigated the relationship between low blood pressure (BP) and attentional performance through the application of a multidimensional diagnostic approach. The authors compared 40 subjects with essential hypotension (mean systolic BP = 97.6 mmHg) with 40 normotensive controls (mean systolic BP = 124.1 mmHg) using 6 computer-based tasks measuring tonic and phasic alertness; selective, divided, and sustained attention; and working memory. To control for possible confounders, the authors used a test battery examining motor performance and a mood questionnaire. BP was monitored continuously during the entire experiment. Hypotensives showed prolonged execution times in each of the attentional tasks (p < .001). Moderately decreased accuracy was found in the tests assessing sustained attention (p = .059) and working memory (p = .012). Moreover hypotensives showed smaller elevations in BP during the execution of the cognitive tasks. This study is the first to demonstrate the relationship between BP and cognitive performance while controlling for motor function and mood.

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