Role of frontal cortex in attentional capture by singleton distractors

The role of frontal cortex in selective attention to visual distractors was examined in an attentional capture task in which participants searched for a unique shape in the presence or absence of an additional colour singleton distractor. The presence of the additional singleton was associated with slower behavioural responses to the shape target, and a greater neural signal in inferior frontal gyrus. To investigate the involvement of cognitive control functions of the frontal lobes in the capture of attention by the additional singletons, we measured the effect of the additional singleton in a context of either low or high working memory load. Whereas behavioural capture was unaffected by the level of load on working memory, greater activity associated with the presence of the additional singleton was observed in inferior frontal gyrus, but only under high load. This effect was greater in participants who experienced greater capture. We argue that the role of inferior frontal gyrus in selective attention is to detect potential sources of distraction.     

Differential effects of differing intensities of acute exercise on speed and accuracy of cognition: A meta-analytical investigation

The primary purpose of this study was to examine, using meta-analytical techniques, the differential effects of differing intensities of acute exercise on speed and accuracy of cognition. Overall, exercise demonstrated a small, significant mean effect size (g = 0.14, p < 0.01) on cognition. Examination of the comparison between speed and accuracy dependent variables showed that speed accounted for most of the effect. For speed, moderate intensity exercise demonstrated a significantly larger mean effect size than those for low and high intensities. For speed of processing during moderate intensity exercise, central executive tasks showed a larger effect size than recall and alertness/attention tasks; and mean effect size for counterbalanced or randomized studies was significantly greater than for studies in which a pre-exercise followed by during or post-exercise protocol was used. There was no significant difference between mean effect sizes when testing took place post-exercise compared to during exercise for speed but accuracy studies demonstrated a significantly larger mean effect size post-exercise. It was concluded that increased arousal during moderate intensity exercise resulted in faster speed of processing. The very limited effect on accuracy may be due to the failure to choose tests which are complex enough to measure exercise-induced changes in accuracy of performance.     

Reducing self‐control depletion effects through enhanced sensitivity to implementation: Evidence from fMRI and behavioral studies

Research suggests self-control relies on a limited set of resources that can be diminished by use. Recent theories posit that there are two stages of self-control: recognizing the need for control and implementing controlled responses. We conducted a functional magnetic resonance imaging experiment and an intervention experiment to investigate whether one or both stages were affected by the prior exercise of self-control. Results from both experiments indicated that only the implementation stage was affected. Further, we demonstrate that self-control can be increased by an intervention designed to boost implementation, as opposed to the recognition of the need to control one's responses.     

Inhibitory Control in Children with Frontal Infarcts Related to Sickle Cell Disease

Evidence from past studies indicates that children with traumatic brain injury experience difficulties with inhibitory control. Less is known about inhibitory control in children with frontal brain injury related to cerebral infarction. We compared the inhibitory performance of children with frontal infarcts related to sickle cell disease with that of a control group of children with sickle cell disease but no history of cerebral infarction. On a stimulus-response reversal task, children with frontal infarcts made significantly more accuracy errors in the inhibitory condition than controls. Findings from this study and from previous research suggest that impairments in inhibitory control are common following frontal injury in a range of pediatric populations.     

Executive function as a function of sub-clinical psychopathy

Some aspects of executive function are thought to be dysfunctional in psychopathic individuals. We administered a small battery of neuropsychological tests (spatial alternation task, object alternation task, and Porteus Maze) to two samples of college students and obtained a measure of psychopathy via a self-report questionnaire. Psychopathic traits were related to the tests of object alternation and Porteus Maze but not to the spatial alternation task. Our results support the hypothesis of orbitofrontal cortex (OFC) dysfunction with sparing of dorsolateral prefrontal cortex (DLPFC) in psychopathy and provide a downward extension of this theory to sub-clinical levels of psychopathy.     

Differentiating core and co-opted mechanisms in calculation: The neuroimaging of calculation in aphasia

The role of language in exact calculation is the subject of debate. Some behavioral and functional neuroimaging investigations of healthy participants suggest that calculation requires language resources. However, there are also reports of individuals with severe aphasic language impairment who retain calculation ability. One possibility in resolving these discordant findings is that the neural basis of calculation has undergone significant reorganization in aphasic calculators. Using fMRI, we examined brain activations associated with exact addition and subtraction in two patients with severe agrammatic aphasia and retained calculation ability. Behavior and brain activations during two-digit addition and subtraction were compared to those of a group of 11 healthy, age-matched controls. Behavioral results confirmed that both patients retained calculation ability. Imaging findings revealed individual differences in processing, but also a similar activation pattern across patients and controls in bilateral parietal cortices. Patients differed from controls in small areas of increased activation in peri-lesional regions, a shift from left fronto-temporal activation to the contralateral region, and increased activations in bilateral superior parietal regions. Our results suggest that bilateral parietal cortex represents the core of the calculation network and, while healthy controls may recruit language resources to support calculation, these mechanisms are not mandatory in adult cognition.     

The decomposition of visual binding over time: Neuropsychological evidence from illusory conjunctions after posterior parietal damage

Patients with Bálint's syndrome are known to make abnormal numbers of illusory conjunctions (ICs) when presented with multiple stimuli and asked to report the features of one. We used two converging procedures to assess the time course of these errors. In Experiments 1 and 2 the errors produced by a patient with Bálint's syndrome, GK, were examined as a function of when he responded. We find that ICs were present even in GK's fastest responses, but that they also increased when GK responded slowly. In Experiment 3 we varied the exposure duration of the stimuli. With short stimulus exposures GK made ICs that he was certain were correct. With longer exposures there was an increase in the number of ICs where GK expressed uncertainty. In contrast to these “uncertain” ICs, feature errors decreased as the exposure duration increased. We propose that the ICs present in GK's fastest responses, and that arise with short stimulus exposures, reflect impairments at a first stage of binding. In addition to this, “uncertain” ICs arise on trials with slow responses, and with long exposures, due to performance then being affected by impairments to a second process dependent on bound features being consolidated into a more stable representation. The role of this consolidation process is limited when responses are made rapidly and exposure durations limited. This two-stage account is discussed in relation to other accounts of feature binding.     

现实性监控研究述评

现实性监控是来源记忆的重要组成部分.总结分析表明,现实性监控的研究成果主要体现在如下方面：①学习项目的比例、学习和测验阶段之间的干扰任务、被试的想象能力等均对现实性监控存在一定的影响;②儿童的现实性监控能力随年龄增长而提高,老人的现实性监控能力相对较低;③不同病人在现实性监控中有不同的困难;④内部来源与外部来源提取激活的大脑区域不同,前额区在区分两类项目时的作用明显.今后应在整合研究结论、建立相应认知模型、构建前额区和顶区联合作用的神经网络和应用推广等方面加强研究.