Temporal dissociation between distractors and targets: The impact of residual distractor processing on target responses

The authors manipulated the extent of distractor interference with learned, mapped responses by presenting distractors to participants (N = 16) before, simultaneously with, or after the target. Interference was significantly less when the distractor preceded the target’s presentation by 200 ms than when distractor and target were presented simultaneously. Interference decreased progressively with increasing intervals. For both simultaneous and temporally separated distractor–target presentations, incongruent distractors were associated with the greatest interference, and neutral and congruent distractors interfered to a lesser degree. Distractors at fixation had a crucially greater impact on goal-directed responses to the target than did distractors at periphery. The authors discuss the findings in the context of (a) the time course of the processing of all inputs, (b) the subsequent enhancement of target-related information and responses, and (c) the inhibition of distractor-related information and responses

Neurcognitive, neuroanatomical and neuroendocrine effects of long-term rotating shift work

Sleep disruption, like that experienced by long-term rotating shift workers, is a physiological stressor which causes a variety of adverse physical, psychological and cognitive symptoms. Some cognitive symptoms are thought to be mediated by the direct effect of stress hormones on the hippocampus (fig.1). Regardless of its source, stress provokes endocrine responses in the body that affect the hypothalamic-pituitary-adrenal (HPA) axis. Whereas acute activation of the HPA axis adaptively activates the body’s stress response by increasing cortisol production, prolonged or repeated activation is detrimental to health due to dysregulation of the HPA axis. Cortisol affects the hippocampus, which has a high concentration of glucocorticoid receptors and plays a prominent role in the down-regulation of the HPA axis. Overstimulation of glucocortioid receptors can cause hippocampal atrophy and related cognitive deficits. Research has found that air crew with inadequate recovery time between outbound, transmeridian long-haul flights showed performance decrements on visual memory tasks, reduced hippocampal volumes and increased cortisol levels.1,2 The current study aimed to investigate whether work-related sleep disruption caused similar effects among rotating shift-workers from outside the flight industry (nurses)

Comparing neurocognition in severe chronic schizophrenia and frontotemporal dementia

Objective: Previous research has suggested cognitive similarities between schizophrenia and frontotemporal dementia. In the current study, we compared neurocognition in a group of hospitalised patients with chronic schizophrenia, who may have a more severe form of schizophrenia resembling Emil Kraepelin’s dementia praecox, with patients with frontotemporal dementia. We hypothesised minimal group differences in cognitive performance, and a large overlap in between-group score distributions in each cognitive domain. Methods: Retrospective neuropsychological data for 26 patients with severe chronic schizophrenia and 34 patients with frontotemporal dementia (behavioural variant) was collated. Neuropsychological measures were categorised into 16 cognitive domains. Raw scores were converted into standardised z-scores for each measure, which were then averaged across measures within each domain. In addition to difference analysis, equivalence testing was utilised, whereby overlap percentages were computed to reflect the amount of score distribution overlap in each domain between groups. Results: A statistically significant difference was observed only in the executive function sub-domain of Switching. Small-to-moderate and moderate effect sizes were noted in four other domains. Equivalence testing showed more than 85% of overlap in score distribution in most domains. Conclusions: Our findings suggest that some patients with severe chronic schizophrenia have cognitive deficits similar in degree and pattern to patients with frontotemporal dementia. The few differences observed between both groups of patients are important for differential diagnostic purposes. One limitation is the retrospective nature of the study. Suggestions for future research include longitudinal follow-up studies of these two patient populations and studies of aspects beyond neurocognition. An implication of our findings is that the ‘dementia of schizophrenia’ concept may be applicable to patients with severe chronic schizophrenia. </jats:sec

The impact of Degraded distractors on (Nondegraded) target identification

In this series of experiments, based on Biederman's Recognition by Components theory, we postulate that corners (vertices) of objects are crucial in programming and execution of goal-directed action. We used a distractor interference paradigm to present line drawings of letters (M and W) with distractors (also M and W), which were either nondegraded or degraded (that is, corners or line segments missing). Degraded distractors caused less interference overall (reduced response times and errors) than Nondegraded distractors, when these were presented peripherally or at fixation (Experiments 1 and 2). When presented at fixation, however, distractors with corners missing caused greater interference than distractors with line segments missing. This pattern was not replicated with non-identical, non-mirror reversed stimuli (H and E: Experiment 3). We speculate that corners are critical in determining the extent of distractor interference. When missing from view, and given sufficient attentional resources and structural similarity, they may be reconstructed by the visuomotor system to aid performance to the target