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  • Title: Attentional and sensory effects of lowered levels of intrinsic alertness.
    Author: Matthias E, Bublak P, Costa A, Müller HJ, Schneider WX, Finke K.
    Journal: Neuropsychologia; 2009 Dec; 47(14):3255-64. PubMed ID: 19682470.
    Abstract:
    Low levels of intrinsic alertness are associated with lateralized performance in visual tasks, similar to neglect of the left (ipsilesional) visual hemi-field. However, it is unclear whether reduced alertness produces a specific lateralization of spatial-attentional processes in terms of the prioritization of right- over left-side stimuli, or whether it affects more basic functions of visuo-sensory coding, and/or higher function of the top-down control of selection, of stimuli on the left side. To decide between these alternatives, the present study examined the effects of lowered alertness, induced by a 50-min vigilance task, in a partial-report paradigm of briefly presented letter displays. With only one (unilateral) stimulus in display, no specific hemi-field effects were found under low-alertness conditions, indicating that reduced alertness impairs neither sensory effectiveness nor the top-town control of selection. However, with dual, bilateral stimuli, report accuracy was specifically affected for left-side targets (in subjects who showed comparable performance for both sides under normal-alertness conditions). This pattern can be interpreted in terms of a specific bias in spatial-attentional weighting, where prioritization of stimuli on the right leads to (mild) extinction of targets on the left. Moreover, participants who had a lower general level of alertness also showed a more pronounced re-distribution of weights, evidenced by a more severe imbalance in report accuracy, in a low compared to a normal state of alertness. This suggests that a low general level of intrinsic alertness engenders a specific vulnerability to neglect-like performance with a (mild) left-side extinction.
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