One-step synthesis of bulk quantities of graphene from graphite by femtosecond laser ablation under ambient conditions

Bulk synthesis of few-layer graphene (FLG) for industrial applications still remains a challenge for researchers. Here, we report a very simple technique for bulk synthesis of FLG by femtosecond laser ablation of graphite powder suspended in ethanol without the requirement of a controlled environment. Graphite powder, with an average particle size <20 μm, was suspended uniformly in ethanol and ablated at room temperature using fs pulses (wavelength ~800 nm and an input beam diameter ~8 mm) followed by ultrasonication to obtain FLG with a lateral size of ~1 μm. Raman spectroscopy and high-resolution transmission electron microscopy data confirmed the nature and morphology of the FLG. The quality and number of layers in the FLG could be controlled by tuning the laser parameters.     

Individuals with first‐ever clinical presentation of a lacunar infarction syndrome: Is there an increased likelihood of developing mild cognitive impairment in the first 12 months after stroke?

Patients who have suffered a single clinical lacunar syndrome, in the absence of any previous clinical stroke, have a varying neuroradiological profile. We examined general cognition in 30 nonaphasic first‐ever lacunar syndrome participants, using a battery of standard clinical neuropsychological measures. At a group level, stroke participants did not demonstrate any cognitive impairment relative to well‐matched community‐based controls up to 12 months after stroke. There was also no evidence of increased frequencies of mild cognitive impairment after a single clinical lacunar syndrome relative to matched control participants within the first year post‐stroke. The current findings represent the first investigation of the cognitive outcome of nonaphasic individuals who have a first‐ever clinical lacunar syndrome. It was concluded that a clinically diagnosed first ever stroke event, presenting as a lacunar syndrome, was not associated with an elevated risk of developing mild cognitive impairment 12 months post‐stroke.     

Threat of bodily harm has opposing effects on cognition

Several theoretical frameworks have suggested that anxiety/stress impairs cognitive performance. A competing prediction is made by attentional narrowing models that predict that stress decreases the processing of task-irrelevant items, thus benefiting performance when task-irrelevant information interferes with behavior. Critically, previous studies have not evaluated these competing frameworks when potent emotional manipulations are involved. Here, we used threat of bodily harm preceding a color-word Stroop task to test these claims. We found a basic effect of threat consisting of a slowing down of performance during neutral Stroop trials. Furthermore, both facilitation and interference scores were affected by threat of shock in a way that was consistent with a reduced-distractor effect. Taken together, we interpret our findings in terms of two opposing effects of stress on cognitive performance. Although partly consistent with the attentional narrowing hypothesis, both resource models and cognitive breadth models require revision in order to account for the results.     

Interactions between cognition and emotion during response inhibition

Cognition and emotion interact to determine ongoing behaviors. In this study, we investigated the interaction between cognition and emotion during response inhibition using the stop-signal task. In Experiment 1, low-threat stop-signals comprising fearful and happy face pictures were employed. We found that both fearful and happy faces improved response inhibition relative to neutral ones. In Experiment 2, we employed high-threat emotional stimuli as stop signals, namely stimuli previously paired with mild shock. In this case, inhibitory performance was impaired relative to a neutral condition. We interpret these findings in terms of the impact of emotional stimuli on early sensory/attentional processing, which resulted in improved performance (Experiment 1), and in terms of their impact at more central stages, which impaired performance (Experiment 2). Taken together, our findings demonstrate that emotion can either enhance or impair cognitive performance depending on the emotional potency of the stimuli involved.     

How does a child solve 7 + 8? Decoding brain activity patterns associated with counting and retrieval strategies

Cognitive development and learning are characterized by diminished reliance on effortful procedures and increased use of memory-based problem solving. Here we identify the neural correlates of this strategy shift in 7-9-year-old children at an important developmental period for arithmetic skill acquisition. Univariate and multivariate approaches were used to contrast brain responses between two groups of children who relied primarily on either retrieval or procedural counting strategies. Children who used retrieval strategies showed greater responses in the left ventrolateral prefrontal cortex; notably, this was the only brain region which showed univariate differences in signal intensity between the two groups. In contrast, multivariate analysis revealed distinct multivoxel activity patterns in bilateral hippocampus, posterior parietal cortex and left ventrolateral prefrontal cortex regions between the two groups. These results demonstrate that retrieval and counting strategies during early learning are characterized by distinct patterns of activity in a distributed network of brain regions involved in arithmetic problem solving and controlled retrieval of arithmetic facts. Our findings suggest that the reorganization and refinement of neural activity patterns in multiple brain regions plays a dominant role in the transition to memory-based arithmetic problem solving. Our findings further demonstrate how multivariate approaches can provide novel insights into fine-scale developmental changes in the brain. More generally, our study illustrates how brain imaging and developmental research can be integrated to investigate fundamental aspects of neurocognitive development.     

Counteracting effect of threat on reward enhancements during working memory

Cognitive performance has been shown to be enhanced when performance-based rewards are at stake. On the other hand, task-irrelevant threat processing has been shown to have detrimental effects during several cognitive tasks. Crucially, the impact of reward and threat on cognition has been studied largely independently of one another. Hence, our understanding of how reward and threat simultaneously contribute to performance is incomplete. To fill in this gap, the present study investigated how reward and threat interact with one another during a cognitive task. We found that threat of shock counteracted the beneficial effect of reward during a working memory task. Furthermore, individual differences in self-reported reward-sensitivity and anxiety were linked to the extent to which reward and threat interacted during behaviour. Together, the current findings contribute to a limited but growing literature unravelling how positive and negative information processing jointly influence cognition.     

Beyond intravenous thrombolysis

The National Institute of Neurological Disorders and Stroke trial of recombinant tissue plasminogen activator has been considered a landmark study in the acute treatment of ischemic stroke. Unfortunately, only a small percentage of all ischemic stroke patients presents to the hospital in time to receive the drug. Moreover, the recannalization rate of a major artery occlusion, such as the proximal middle cerebral artery or top of the internal carotid artery occlusion, after intravenous (IV) thrombolytic therapy has been disappointingly low. Since the Food and Drug Administration's approval of IV plasminogen activator, there have been numerous randomized clinical trials investigating the safety and efficacy of different thrombolytics administered in various time frames. In addition to the IV administration, efforts have been made in order to study the radiographic as well as clinical effects of intra-arterial (IA) thrombolysis. The combination of IV and IA thrombolysis has been studied. For patients who do not qualify for receiving chemical thrombolysis, new devices have been developed for mechanical thrombectomy. Angioplasty and stenting procedures are being performed more frequently than in the past as one of the treatment modalities for acute ischemic stroke patients. Relentless research effort is being made internationally in order to fight the devastating disease which now goes beyond the conventional IV thrombolysis.     

Moment-to-moment fluctuations in fMRI amplitude and interregion coupling are predictive of inhibitory performance

We investigated how moment-to-moment fluctuations in fMRI amplitude and interregional coupling are linked to behavioral performance during a stop signal task. To quantify the relationship between single-trial amplitude and behavior on a trial-by-trial basis, we modeled the probability of successful inhibition as a function of response amplitude via logistic regression analysis. At the group level, significant logistic slopes were observed in, among other regions, the inferior frontal gyrus (IFG), caudate, and putamen, all bilaterally. Furthermore, we investigated how trial-by-trial fluctuations in responses in attentional regions covaried with fluctuations in inhibition-related regions. The coupling between several frontoparietal attentional regions and the right IFG increased during successful versus unsuccessful performance, suggesting that efficacious network interactions are important in determining behavioral outcome during the stop signal task. In particular, the link between responses in the right IFG and behavior were moderated by moment-to-moment fluctuations in evoked responses in the left intraparietal sulcus. A supplemental figure for this article may be downloaded from http:// cabn.psychonomic-journals.org/content/supplemental.