Variability of response times as a marker of diverted attention

Abstract

propose that this lack of consistency is an important determinant of patients' behaviour, and may result from a deficit independent of other mechanisms causing neglect. Here we suggest that an increase of variability, and not only of RTs, is to be expected when attention is exogenously biased away from the probed location. Consequently, space-based variability can be interpreted in the framework of existing models of unilateral neglect. According to one such model, a basic impairment in left neglect is a bias toward rightward exogenous orienting of attention. As a result, left targets often fail to rapidly capture patients' attention, thus yielding slow RTs. However, since the probability for a left target attracting attention is low but not null, relatively fast RTs can occur on those rare occasions in which a left target does capture patients' attention. The coexistence of these relatively fast with slow RTs could be at the basis of space-based variability in neglect. Empirical support for our hypothesis comes from the results of a re-analysis for variability of cued RTs obtained in 18 normal individuals and six left neglect patients. Cues were peripheral and non-informative, thus eliciting an exogenous attentional shift. For normal individuals, invalid trials yielded less consistent response times than valid trials at short (150 ms) cue-target interval; for neglect patients, a similar phenomenon occurred for left invalidly-cued targets, thus paralleling the disproportionate cost in RTs typically evoked by this condition in unilateral neglect. We conclude by discussing some possible determinants of gradient-shaped effects and by outlining the implications of space-based variability for current models of unilateral neglect.

The Predictive Brain State: Asynchrony in Disorders of Attention?

“…Right IPL lesions produce neglect of the contralateral hemifield. But even here, a gradient of IIV can be observed with performance variability greatest for the most eccentric locations (Anderson and others 2000; Bartolomeo and others 2001). …”

Orienting of attention in left unilateral neglect

“…Recall that in this experiment cues were peripheral and non-informative, thus eliciting an exogenous attentional shift. The re-analysis [114], whose results are displayed in Fig. 7, showed that, for normal individuals, invalid trials yielded less consistent response times than valid trials at short (150 ms) SOA, that is, the time interval most likely concerned with exogenous attentional shifts.…”

Fast responses to neglected targets in visual search reflect pre-attentive processes: an exploration of response times in visual neglect

“…Some studies have also observed that the speed of response tends to be rather variable in these neglect patients [2,5,60]. One interesting phenomenon is that, despite the fact that a patient's response is generally slow, one occasionally observes rather fast RTs to left-sided targets.…”

“…One interesting phenomenon is that, despite the fact that a patient's response is generally slow, one occasionally observes rather fast RTs to left-sided targets. This may not be surprising if we do not simply view the damage to attention as an all-or-none phenomenon, so that the actual probability of a left target of capturing attention is never zero [2,5]. Indeed, it is now clear that spatial attention is modulated by other more general attentional factors, such as arousal or alertness [74][75][76]80].…”