The effects of dividing attention on smooth pursuit eye tracking

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The antisaccade task as a research tool in psychopathology: A critical review

The antisaccade task is a measure of volitional control of behavior sensitive to fronto-striatal dysfunction. Here we outline important issues concerning antisaccade methodology, consider recent evidence of the cognitive processes and neural mechanisms involved in task performance, and review how the task has been applied to study psychopathology. We conclude that the task yields reliable and sensitive measures of the processes involved in resolving the conflict between volitional and reflexive behavioral responses, a key cognitive deficit relevant to a number of neuropsychiatric conditions. Additionally, antisaccade deficits may reflect genetic liability for schizophrenia. Finally, the ease and accuracy with which the task can be administered, combined with its sensitivity to fronto-striatal dysfunction and the availability of suitable control conditions, may make it a useful benchmark tool for studies of potential cognitive enhancers

Keeping an eye on the truth: Pupil size, recognition memory and malingering

Background: Estimates of the incidence of malingering in patient populations vary from 1 to 12%, rising to ∼25% in patients seeking financial compensation. Malingering is particularly difficult to detect when patients feign poor performance on neuropsychological tests (see Hutchinson, 2001). One strategy to detect malingering has been to identify psychophysiological markers associated with deception. Tardif, Barry, Fox and Johnstone (2000) used electroencephalogram (EEG) recording to measure event related potentials (ERPs) during a standard recognition memory test. Previous research has documented an ERP “old/new effect” – late positive parietal ERPs are larger when participants view old, learned words compared to new words during recognition. Tardif et al. reasoned that if this effect is not under conscious control, then it should be equally detectable in people feigning amnesia as in participants performing to their best ability. As predicted, they found no difference in the magnitude and topography of the old/new ERP effect between participants who were asked to feign amnesia whilst performing the test and those asked to perform to their best ability. Whilst this approach shows some promise, EEG is comparatively time consuming and expensive. Previous research has shown that during recognition memory tests, participants' pupils dilate more when they view old items compared to new items (Otero, Weeks, and Hutton, 2006; Vo et al., 2008). This pupil “old/new effect” may present a simpler means by which to establish whether participants are feigning amnesia. Method: We used video-based oculography to compare changes in pupil size during a recognition memory test when participants were given standard recognition memory instructions, instructions to feign amnesia and instructions to report all items as new. Due to constant fluctuation in pupil size over time, and variation between individuals, a pupil dilation ratio (PDR) was calculated that represented the maximum pupil size during the trial as a proportion of the maximum during baseline. Results: Participants' pupils dilated more to old items compared to new items under all three instruction conditions (F(1.25) = 47.02, MSE < 0.001, p < .001, ηp2 = .65). There were no significant differences between baseline pupil size (F(1.63,40.76) = 1.90, p = .17, ns). Conclusions: The finding that under standard recognition memory instructions, participants' relative increase in pupil size is greater when they view old items compared to new items replicates previous research documenting the pupil old/new effect. That the effect persists, even when participants give erroneous responses during recognition, suggests that the “pupil old/new effect” is not under conscious control and may therefore have potential use in clinical settings as a simple means with which to detect whether patients are feigning amnesia

The Effects of Individual Differences on Cued Antisaccade Performance

In the antisaccade task, pre-cueing the location of a correct response has the paradoxical effect of increasing errors. It has been suggested that this effect occurs because participants adopt an "antisaccade task set" and treat the cue as if was a target - directing attention away from the precue and towards the location of the impending target. This hypothesis was tested using a mixed pro / antisaccade task. In addition the effects of individual differences in working memory capacity and schizotypal personality traits on performance were examined. Whilst we observed some modest relationships between these individual differences and antisaccade performance, the strongest predictor of antisaccade error rate was uncued prosaccade latency

Mini Review: Potential Applications of Non-host Resistance for Crop Improvement

Plant breeding for disease resistance is crucial to sustain global crop production. For decades, plant breeders and researchers have extensively used host plant resistance genes (R-genes) to develop disease resistant cultivars. However, the general instability of R-genes in crop cultivars when challenged with diverse pathogen populations emphasizes the need for more stable means of resistance. Alternatively, nonhost resistance is recognized as the most durable, broad-spectrum form of resistance against the majority of potential pathogens in plants and has gained great attention as an alternative target for managing resistance. While transgenic approaches have been utilized to transfer nonhost resistance to host species, conventional breeding applications have been more elusive. Nevertheless, avenues for discovery and deployment of genetic loci for nonhost resistance via hybridization are increasingly abundant, particularly when transferring genes among closely related species. In this mini review, we discuss current and developing applications of nonhost resistance for crop improvement with a focus on the overlap between host and nonhost mechanisms and the potential impacts of new technology

Executive function in first-episode schizophrenia

BACKGROUND: We tested the hypothesis that schizophrenia is primarily a frontostriatal disorder by examining executive function in first-episode patients. Previous studies have shown either equal decrements in many cognitive domains or specific deficits in memory. Such studies have grouped test results or have used few executive measures, thus, possibly losing information. We, therefore, measured a range of executive ability with tests known to be sensitive to frontal lobe function. METHODS: Thirty first-episode schizophrenic patients and 30 normal volunteers, matched for age and NART IQ, were tested on computerized test of planning, spatial working memory and attentional set shifting from the Cambridge Automated Neuropsychological Test Battery. Computerized and traditional tests of memory were also administered for comparison. RESULTS: Patients were worse on all tests but the profile was non-uniform. A componential analysis indicated that the patients were characterized by a poor ability to think ahead and organize responses but an intact ability to switch attention and inhibit prepotent responses. Patients also demonstrated poor memory, especially for free recall of a story and associate learning of unrelated word pairs. CONCLUSIONS: In contradistinction to previous studies, schizophrenic patients do have profound executive impairments at the beginning of the illness. However, these concern planning and strategy use rather than attentional set shifting, which is generally unimpaired. Previous findings in more chronic patients, of severe attentional set shifting impairment, suggest that executive cognitive deficits are progressive during the course of schizophrenia. The finding of severe mnemonic impairment at first episode suggests that cognitive deficits are not restricted to one cognitive domain

Using event-related fMRI to examine sustained attention processes and effects of APOE ε4 in young adults

In this study we investigated effects of the APOE ε4 allele (which confers an enhanced risk of poorer cognitive ageing, and Alzheimer’s Disease) on sustained attention (vigilance) performance in young adults using the Rapid Visual Information Processing (RVIP) task and event-related fMRI. Previous fMRI work with this task has used block designs: this study is the first to image an extended (6-minute) RVIP task. Participants were 26 carriers of the APOE ε4 allele, and 26 non carriers (aged 18–28). Pupil diameter was measured throughout, as an index of cognitive effort. We compared activity to RVIP task hits to hits on a control task (with similar visual parameters and response requirements but no working memory load): this contrast showed activity in medial frontal, inferior and superior parietal, temporal and visual cortices, consistent with previous work, demonstrating that meaningful neural data can be extracted from the RVIP task over an extended interval and using an event-related design. Behavioural performance was not affected by genotype; however, a genotype by condition (experimental task/control task) interaction on pupil diameter suggested that ε4 carriers deployed more effort to the experimental compared to the control task. fMRI results showed a condition by genotype interaction in the right hippocampal formation: only ε4 carriers showed downregulation of this region to experimental task hits versus control task hits. Experimental task beta values were correlated against hit rate: parietal correlations were seen in ε4 carriers only, frontal correlations in non-carriers only. The data indicate that, in the absence of behavioural differences, young adult ε4 carriers already show a different linkage between functional brain activity and behaviour, as well as aberrant hippocampal recruitment patterns. This may have relevance for genotype differences in cognitive ageing trajectories

The long-term sustainability of a respiratory culture nudge

Resource-intensive interventions and education are susceptible to a lack of long-term sustainability and regression to the mean. The respiratory culture nudge changed reporting to Commensal Respiratory Flora only: No S. aureus/MRSA or P. aeruginosa. This study demonstrated sustained reduction in broad-spectrum antibiotic duration and long-term sustainability 3 years after implementation

Acute effects of nicotine on visual search tasks in young adult smokers

Rationale Nicotine is known to improve performance on tests involving sustained attention and recent research suggests that nicotine may also improve performance on tests involving the strategic allocation of attention and working memory. Objectives We used measures of accuracy and response latency combined with eye-tracking techniques to examine the effects of nicotine on visual search tasks. Methods In experiment 1 smokers and non-smokers performed pop-out and serial search tasks. In experiment 2, we used a within-subject design and a more demanding search task for multiple targets. In both studies, 2-h abstinent smokers were asked to smoke one of their own cigarettes between baseline and tests. Results In experiment 1, pop-out search times were faster after nicotine, without a loss in accuracy. Similar effects were observed for serial searches, but these were significant only at a trend level. In experiment 2, nicotine facilitated a strategic change in eye movements resulting in a higher proportion of fixations on target letters. If the cigarette was smoked on the first trial (when the task was novel), nicotine additionally reduced the total number of fixations and refixations on all letters in the display. Conclusions Nicotine improves visual search performance by speeding up search time and enabling a better focus of attention on task relevant items. This appears to reflect more efficient inhibition of eye movements towards task irrelevant stimuli, and better active maintenance of task goals. When the task is novel, and therefore more difficult, nicotine lessens the need to refixate previously seen letters, suggesting an improvement in working memory

The antisaccade task as an index of sustained goal activation in working memory: modulation by nicotine

The antisaccade task provides a laboratory analogue of situations in which execution of the correct behavioural response requires the suppression of a more prepotent or habitual response. Errors (failures to inhibit a reflexive prosaccade towards a sudden onset target) are significantly increased in patients with damage to the dorsolateral prefrontal cortex and patients with schizophrenia. Recent models of antisaccade performance suggest that errors are more likely to occur when the intention to initiate an antisaccade is insufficiently activated within working memory. Nicotine has been shown to enhance specific working memory processes in healthy adults. MATERIALS AND METHODS: We explored the effect of nicotine on antisaccade performance in a large sample (N = 44) of young adult smokers. Minimally abstinent participants attended two test sessions and were asked to smoke one of their own cigarettes between baseline and retest during one session only. RESULTS AND CONCLUSION: Nicotine reduced antisaccade errors and correct antisaccade latencies if delivered before optimum performance levels are achieved, suggesting that nicotine supports the activation of intentions in working memory during task performance. The implications of this research for current theoretical accounts of antisaccade performance, and for interpreting the increased rate of antisaccade errors found in some psychiatric patient groups are discussed