Determining the speed at which a task is performed (i.e., reaction time) can be a valuable tool in both research and clinical assessments. However, standard computer hardware employed for measuring reaction times (e.g., computer monitor, keyboard, or mouse) can add nonrepresentative noise to the data, potentially compromising the accuracy of measurements and the conclusions drawn from the data. Therefore, an assessment of the accuracy and precision of measurement should be included along with the development of computerized tests and assessment batteries that rely on reaction times as the dependent variable. This manuscript outlines three methods for assessing the temporal accuracy of reaction time data (one employing external chronometry). Using example data collected from the Dalhousie Computerized Attention Battery (DalCAB) we discuss the detection, measurement, and correction of nonrepresentative noise in reaction time measurement. The details presented in this manuscript should act as a cautionary tale to any researchers or clinicians gathering reaction time data, but who have not yet considered methods for verifying the internal chronometry of the software and or hardware being used.

Attention is an important, multifaceted cognitive domain that has been linked to three distinct, yet interacting, networks: alerting, orienting, and executive control. The measurement of attention and deficits of attention within these networks is critical to the assessment of many neurological and psychiatric conditions in both research and clinical settings. The Dalhousie Computerized Attention Battery (DalCAB) was created to assess attentional functions related to the three attention networks using a range of tasks including: simple reaction time, go/no-go, choice reaction time, dual task, flanker, item and location working memory, and visual search. The current study provides preliminary normative data, test-retest reliability (intraclass correlations) and practice effects in DalCAB performance 24-h after baseline for healthy young adults (n = 96, 18-31 years). Performance on the DalCAB tasks demonstrated Good to Very Good test-retest reliability for mean reaction time, while accuracy and difference measures (e.g., switch costs, interference effects, and working memory load effects) were most reliable for tasks that require more extensive cognitive processing (e.g., choice reaction time, flanker, dual task, and conjunction search). Practice effects were common and pronounced at the 24-h interval. In addition, performance related to specific within-task parameters of the DalCAB sub-tests provides preliminary support for future formal assessment of the convergent validity of our interpretation of the DalCAB as a potential clinical and research assessment tool for measuring aspects of attention related to the alerting, orienting, and executive control networks.

Using experimentally validated tests to measure the vigilance/alerting, orienting and executive control attention networks, we have developed a novel, theoretically driven battery for measuring attentional abilities, called the Dalhousie Computerized Attention Battery (DalCAB). The current study sought to examine the factor structure of the DalCAB as preliminary evidence for its validation as an assessment tool for the above-named attention networks. One hundred young, healthy adult participants (18 to 31 years) completed the DalCAB (simple reaction time, choice reaction time, dual task, go/no-go, visual search, vertical flanker, and item memory tasks). Exploratory factor analysis of task performance with promax rotation highlighted a 9-factor model, accounting for 54.66% of the shared variance. Factors 1, 2, and 5 are associated with measures reflecting the vigilance/alerting network (response speed, maintenance/preparation and consistency, respectively), Factor 3 is associated with the orienting network (searching measures). Factors 4, 6, 7, and 8 are associated with different aspects of the executive control network including: inhibition, working memory, filtering, and switching. The final factor is associated with vigilance/alerting (fatigue) and executive control (proactive interference). Our model provides preliminary evidence for the validation of our interpretation of the DalCAB as a measure of vigilance/alerting, orienting, and executive control attentional abilities, and contributes to the previously reported evidence for the validation of these tasks for measuring different aspects of attention. We also demonstrate the importance of each of the specific measures derived from the DalCAB tasks, and our results provide further behavioral evidence of the existence of multiple attention-related networks.

A deficit disengaging attention from the ipsilesional space in order to re-orient toward the contralesional space has been reported after right-hemisphere stroke (disengage deficit) and has been related to the severity of visuospatial neglect. Neglect rehabilitation studies have shown that left limb movements improve leftward orienting; the effect, however, is variable, and the mechanism of improvement is uncertain. Thus, this study examined whether limb movements specifically reduce the underlying disengage deficit of attention after right-hemisphere stroke. The effects of active and passive limb movements (vs. no limb movement) on orienting were examined using a covert exogenously cued orienting task in groups of right-hemisphere stroke patients with and without a significant disengage deficit (DD+, DD−) and healthy older adults. As previously seen, disengage deficit scores of stroke patients were positively correlated with the severity of neglect. The leftward disengage deficit was not affected by either active or passive limb movements, however, although movements did have both alerting and distracting effects on other aspects of orienting. Thus, our results suggest that the benefits of limb movements may not be related to changes in the underlying disengage deficit, but may impact other processes that underlie left-sided orienting (e.g., arousal and voluntary strategies).

Inattentional blindness is described as the failure to perceive a supra-threshold stimulus when attention is directed away from that stimulus. Based on performance on an explicit recognition memory test and concurrent functional imaging data Rees, Russell, Frith, and Driver [Rees, G., Russell, C., Frith, C. D., & Driver, J. (1999). Inattentional blindness versus inattentional amnesia for fixated but ignored words. Science, 286, 2504–2507] reported inattentional blindness for word stimuli that were fixated but ignored. The present study examined both explicit and implicit memory for fixated but ignored words using a selective-attention task in which overlapping picture/word stimuli were presented at fixation. No explicit awareness of the unattended words was apparent on a recognition memory test. Analysis of an implicit memory task, however, indicated that unattended words were perceived at a perceptual level. Thus, the selective-attention task did not result in perfect filtering as suggested by Rees et al. While there was no evidence of conscious perception, subjects were not blind to the implicit perceptual properties of fixated but ignored words.

Previous studies of visual search patterns in visuospatial neglect have analyzed shifts of attention during search tasks using eye tracking technology and verbal reports. The purpose of the present study was to replicate and extend upon reported parameters of visual scanning patterns of neglect patients in peripersonal space (within arms reach) and to examine whether similar patterns of visual search are also apparent in extrapersonal space (beyond arms reach). Using a simple verbal visual search and target detection paradigm right-hemisphere stroke participants, with and without neglect, and healthy older volunteers named targets on scanning sheets placed in peripersonal and extrapersonal space. The healthy controls and right-hemisphere stroke group without neglect showed similar ‘reading’ type strategies, while the neglect group displayed an unsystematic search pattern, during search in both peripersonal and extrapersonal space. Group comparisons of search parameters support the presence of multiple cognitive deficits affecting the complex visual search patterns of neglect patients, including a rightward attentional bias, a reduced spatial scale of attention (local processing bias), and a deficit of working memory affecting both near and far space search. Ventral visual stream damage and neglect, however, were related to slower target report rate and more misidentification errors in extrapersonal space. The ease of administration of this verbal target detection task in both peripersonal and extrapersonal space, and the relationship of the measures produced to theorized attentional and executive deficits in neglect, provide impetus for further research on the severity and independence of individual scanning deficits in neglect.

PURPOSESpatial neglect is common after right-hemisphere stroke and has proven resilient to a number of therapeutic interventions. Both active and experimenter-induced passive movements of the left limb in left hemispace have been shown to ameliorate neglect in subsets of patients by improving performance on tasks requiring attention to the left side of space. However, the high incidence of contralesional hemiparesis and poor motor recovery in neglect makes active limb movement therapies applicable to only a small subset of patients. The purpose of our studies was to investigate the effects of passive movements of the left hand by functional electrical stimulation (FES), a common and portable motor rehabilitation technique, on performance in a visual scanning task.METHODSThe effect of FES-induced passive movement on target detection in a visual scanning task was compared to no movement and active movement conditions and also investigated in scanning tasks in both near and far space.RESULTSPassive limb movement effects in neglect were variable across and within studies, reference spaces, and individuals, with a subset of positive responders differing from non-responders in regard to constructional deficits and lesion location.CONCLUSIONSThe potential viability of FES as a therapy for neglect deserves further investigation and directions for future research in this area are discussed.

Previous studies of target-cancellation performance in visuospatial neglect patients have reported lateral (left–right) and radial (near–far) gradients of attentional ability. The purpose of the present study was to replicate the reported attentional gradients in peripersonal space (within arms reach) and to examine whether lateral gradients of detection also appear in extrapersonal space (beyond arms reach), using equivalent tasks with no manual requirement. The relationship between radial gradients in peripersonal space and neglect severity (degree of lateral gradient) in extrapersonal space was also of interest. Right-hemisphere stroke subjects, with and without neglect, and healthy control subjects named visual targets on scanning sheets placed in peripersonal and extrapersonal space. The neglect group showed lateral gradients of increasing target detection from left to right in both peripersonal and extrapersonal space, which were not evident in the performance of either of the control groups. Double dissociations of neglect severity in peripersonal and extrapersonal space were also found in analyses of individual performance. Lesion analyses showed that peripersonal neglect was related to dorsal stream damage and extrapersonal neglect was related to ventral stream damage. Group analyses showed no significant radial gradients in peripersonal space in the three groups. In addition, while analyses of some individuals found significant near–far and far-near radial gradients, there was no correlation between radial gradients in peripersonal space and neglect severity in extrapersonal space. These results are discussed in terms of theorised hemispheric mechanisms of spatial attention and the relationship of neglect in the two co-ordinate spaces to the extent and location of damaged neurons in the right hemisphere.

OBJECTIVE:To assess the efficacy of passive and active limb movement to improve visual scanning in patients with hemispatial neglect.DESIGN:Before-after trial: behavioral analyses of a case series.SETTING:Stroke rehabilitation unit in a tertiary care hospital.PARTICIPANTS:Nine individuals with right-hemisphere stroke (mean time poststroke, 19.5 mo) and left-sided neglect, as assessed by the Sunnybrook Bedside Neglect Battery.INTERVENTION:Active left limb movement (button push; n=3) or passive left limb movement (n=8) with functional electric stimulation (FES) administered during visual scanning testing.MAIN OUTCOME MEASURES:Performance on visual scanning tests involving naming of letters and numbers.RESULTS:Both active and passive movement significantly improved target detection on the left side, but not on the right side, on the visual scanning task. Positive results were seen in 2 of 3 active movement patients and 6 of 8 passive movement patients.CONCLUSIONS:Both active and FES-stimulated passive movements are potential techniques for the treatment of hemispatial neglect.

1 引言 单侧疏忽是脑损伤后的一种认知和行为障碍综合征,它可能严重影响患者的痊愈、康复的成功和独立生活的长久重建.对转归的研究表明,疏忽及其相关后果通常以患者不能自理,依赖性增强和生活质量降低等预示卒中预后不良.