Evidence cerebral blood-flow regulation mediates exercise-cognition links in healthy young adults

OBJECTIVE

Healthy young adults are presumed to be in their cognitive prime, yet emerging evidence indicates that regular engagement in physical activity can still benefit their cognitive functioning. The mechanisms supporting these exercise-related cognitive benefits remain unclear, but recent research points to cerebral blood-flow (CBF) regulation as potentially important. The current study investigated the possibility that efficacy of CBF regulation underpins exercise-cognition links in this high functioning population.

METHOD

In 55 healthy young adults, cognitive control performance (inhibition and switching) was examined in relation to habitual physical activity, aerobic fitness, and CBF regulation (evidenced by blood-flow responsiveness to increases and decreases in carbon dioxide: hypercapnic reactivity, n = 43, and hypocapnic reactivity, n = 42).

RESULTS

Multiple regression analyses revealed that more frequent physical activity, and to some extent better aerobic fitness, predicted both better CBF regulation and better cognitive inhibitory control. CBF regulation also predicted better cognitive inhibitory control. Moreover, mediation analyses indicated that more frequent participation in physical activity may bring about improvements in cognitive inhibitory control through improved CBF regulation.

CONCLUSION

These results provide novel insight into the cognitive and cerebrovascular benefits that may be gained with regular engagement in physical activity, even in a high-functioning population. Moreover, they point to better CBF regulation as a specific mechanism that may drive physical activity-related cognitive benefits, which converges with recent data in older women (Brown et al., 2010).

Evidence inhibition responds reactively to the salience of distracting information during focused attention

Along with target amplification, distractor inhibition is regarded as a major contributor to selective attention. Some theories suggest that the strength of inhibitory processing is proportional to the salience of the distractor (i.e., inhibition reacts to the distractor intensity). Other theories suggest that the strength of inhibitory processing does not depend on the salience of the distractor (i.e., inhibition does not react to the distractor intensity). The present study aimed to elucidate the relationship between the intensity of a distractor and its subsequent inhibition during focused attention. A flanker task with a variable distractor-target stimulus-onset asynchrony (SOA) was used to measure both distractor interference and distractor inhibition. We manipulated the intensity of the distractor in two separate ways, by varying its distance from the target (Experiment 1) and by varying its brightness (Experiment 2). The results indicate that more intense distractors were associated with both increased interference and stronger distractor inhibition. The latter outcome provides novel support for the reactive inhibition hypothesis, which posits that inhibition reacts to the strength of distractor input, such that more salient distractors elicit stronger inhibition.

Identity-based inhibitory processing during focused attention

Recent data suggest that the operating principles governing inhibition of distractor-related activity may deviate from dominant models describing inhibitory processing during selective attention. Here we aimed to gain a better understanding of these data in order to determine whether they actually defy premises of current models. In addition to providing evidence against noninhibitory accounts of the data (see especially Experiment 6), the results support three main novel findings that challenge current theories. First, the data provide evidence that inhibition overpowered excitation from ongoing external input (Experiments 1-4), which suggests that inhibitory control processes are more powerful than current models indicate. Second, negative effects emerged even when targets appeared alone (Experiment 5), which suggests that selection does not play an essential role in triggering inhibitory processing. Third, relatively early distractor-related activity was affected, which supports a role for inhibition prior to action control (Experiment 3). These findings suggest a need to revise current models describing inhibition of distracting information during selective attention.

Famous faces demand attention due to reduced inhibitory processing

People have particular difficulty ignoring distractors that depict faces. This phenomenon has been attributed to the high level of biological significance that faces carry. The current study aimed to elucidate the mechanism by which faces gain processing priority. We used a focused attention paradigm that tracks the influence of a distractor over time and provides a measure of inhibitory processing. Upright famous faces served as test stimuli and inverted versions of the faces as well as upright non-face objects served as control stimuli. The results revealed that although all of the stimuli elicited similar levels of distraction, only inverted distractor faces and non-face objects elicited inhibitory effects. The lack of inhibitory effects for upright famous faces provides novel evidence that reduced inhibitory processing underlies the mandatory nature of face processing.

Impaired control of the oculomotor reflexes in Parkinson's disease

To investigate the role of the basal ganglia in integrating voluntary and reflexive behaviour, the current study examined the ability of patients with Parkinson's disease to voluntarily control oculomotor reflexes. We measured the size of the fixation offset effect (the reduction in saccadic reaction time when a fixation point is removed) during a block of pro- and a block of anti-saccades. Healthy controls showed the expected reduction of the FOE during the anti-saccades, which results from efforts to suppress reflexive eye movements (a preparatory set characterized by increased internal control and reduced external control). However, there was no reduction of the FOE in the anti-saccade task in Parkinson's patients, indicating that they are impaired in exerting control over oculomotor reflexes.

Use of pulp mill inorganic wastes as alternative liming materials

A laboratory aerobic incubation study was performed during 18 weeks under controlled conditions to assess the effects of applying different doses of pulp mill inorganic wastes on the physical-chemical properties of an acid Dystric Cambissol. Three different inorganic wastes were tested - wood ash, dregs and grits, and an agriculture limestone was used as reference. Results showed that increasing the dose applied of the different inorganic wastes tested always led to significant raises of soil pH at different incubation times demonstrating that its use as alternative-liming materials could be a valid and less expensive option to the use of commercial agricultural limestone. Moreover, no immediate concerns seem to be expected related to soil exchangeable sodium (Na) content, at least for the doses needed to increase soil pH until the targeted value 6.5. Particularly for wood ash a pronounced increase on soil extractable potassium and phosphorous was observed, indicating that besides the liming effect this waste can contribute to improve soil fertility by supplying significant available amounts of these nutrients. Finally, metals do not seem to be a limiting factor for the application to land of these by-products.

Action planning in the presence of distracting stimuli: an investigation into the time course of distractor effects

Humans have a remarkable capability to respond efficiently to a stimulus of interest despite other stimuli competing for neural resources. The current study investigated how the human system copes with distracting stimuli. During each trial, participants viewed 2 sequential stimuli that were each associated with a specific action based on an arbitrary mapping. The 1st stimulus served as a distractor, and the 2nd stimulus required a response (target). When the distractor preceded the target by more than a few hundred milliseconds, response latencies were slower when the 2 stimuli were associated with the same response. The authors propose that this negative compatibility effect stemmed from an inhibitory mechanism that the human system utilizes to prevent the distractor from eliciting an unwanted response.

The role of the human pulvinar in visual attention and action: evidence from temporal-order judgment, saccade decision, and antisaccade tasks

The pulvinar nucleus of the thalamus has been considered as a key structure for visual attention functions (Grieve, K.L. et al. (2000). Trends Neurosci., 23: 35-39; Shipp, S. (2003). Philos. Trans. R. Soc. Lond. B Biol. Sci., 358(1438): 1605-1624). During the past several years, we have studied the role of the human pulvinar in visual attention and oculomotor behaviour by testing a small group of patients with unilateral pulvinar lesions. Here we summarize some of these findings, and present new evidence for the role of this structure in both eye movements and visual attention through two versions of a temporal-order judgment task and an antisaccade task. Pulvinar damage induces an ipsilesional bias in perceptual temporal-order judgments and in saccadic decision, and also increases the latency of antisaccades away from contralesional targets. The demonstration that pulvinar damage affects both attention and oculomotor behaviour highlights the role of this structure in the integration of visual and oculomotor signals and, more generally, its role in flexibly linking visual stimuli with context-specific motor responses.

Predicting outcomes and complications of percutaneous endoscopic gastrostomy

BACKGROUND AND STUDY AIMS

Percutaneous endoscopic gastrostomy (PEG) is the preferred route for long-term enteral feeding. Our aims were to prospectively evaluate the outcome ("PEG status") and complications of PEG and to determine whether these can be predicted by patients' baseline characteristics.

PATIENTS AND METHODS

We conducted a prospective study in two tertiary hospitals between August 2003 and January 2005, enrolling all patients who were undergoing PEG placement. We completed a questionnaire with details of demographic data, diagnosis, indication for PEG, Charlson's co-morbidity index, Barthel's index, laboratory tests, complications, and date and cause of death. Patients were followed at scheduled appointments. Univariate and multivariate analyses were performed.

RESULTS

168 patients (48% male, 52% female; mean age +/- standard deviation 74 +/- 16 years) underwent PEG using the pull technique. The main indication was neurogenic dysphagia (156 patients, 92.9%). Although most indications were appropriate, in half the cases these were established too late. There were no procedure-related deaths. Major complications occurred in four patients (2.4%); minor complications occurred in 52 patients (31%). No single variable could predict complications. Fifteen patients (9%) had the PEG removed. No single variable was independently associated with PEG removal. The mortality was 6.5% at 30 days, 17.3% at 90 days and 33.9% at 1 year. The C-reactive protein was the only predictive factor of early mortality (< or = 30 days), and Charlson's co-morbidity index was the only predictive factor of late mortality (> 30 days).

CONCLUSIONS

PEG placement is an easy and safe procedure, although it is often requested too late. No single variable could predict complications or PEG removal. C-reactive protein was found to be predictive of early mortality and Charlson's index was predictive of late mortality.

Cotyledonoid leiomyoma in pregnancy

BACKGROUND

Benign smooth-muscle tumors (leiomyomata) are the most frequent tumors found in the female genital tract. They are easy to diagnose in pregnancy and usually managed conservatively. Some variant forms with unusual infiltrative growth pattern have been known, but they are rare in pregnancy. The variant forms pose diagnostic and management difficulties.

CASE

An unusual type of leiomyoma (cotyledonoid), adhering to the bowels and occupying the whole left broad ligament, was excised completely at 14 weeks of gestation, and the pregnancy continued to term.

CONCLUSION

Familiarity with benign uterine smooth-muscle tumors with unusual growth patterns by gynecologists and pathologists is essential in avoiding over-treatment.

Improvement of parameters of freezing medium and freezing protocol for bull sperm using two osmotic supports

The aim of this study was to improve the freezing protocol of bull sperm, by investigating the influence on sperm viability after freeze/thawing of different freezing medium components, as well as the effect of cooling rates in the different stages of the cooling protocol, in single factor experiments. The experimental variables were: (1) salt-based versus a sugar-based medium (Tris versus sucrose); (2) glycerol concentration; (3) detergent (Equex) concentration; (4) presence of bicarbonate; (5) rate of cooling from 22 degrees C to holding temperature (CR1); (6) holding temperature (HT); (7) rate of cooling from holding temperature to -6 degrees C (CR2); (8) rate of cooling from -10 to -100 degrees C (CR3). All experiments were performed using five bulls per experiment (three ejaculates per bull). Sperm motility after freezing and thawing was assessed by CASA system, and sperm membrane integrity was assessed by flow cytometry. Sucrose-based medium did not offer a clear significant benefit compared to Tris medium. The concentration of Equex that gave the best results in Tris-based media group and sucrose-based media group was in a range between 2-7 and 4-7 g/l, respectively. In both media groups, a glycerol concentration of 800 mM was the best in any post-thaw viability parameters. In the Tris media group, the presence of bicarbonate had a negative effect on sperm viability. CR1 and CR2 had no significant effect on any of the post-thaw sperm viability parameters, but a CR1=0.2 degrees C/min and CR2=4 degrees C/min appeared to give better results in both media. The holding temperature (HT) that gave the best results was found to be in the range of 5-9 degrees C. There was a significant disadvantage of using a low CR3 of 10 degrees C/min, while 150 degrees C/min appeared to be the best cooling rate for either medium.

3-d interpolation in object perception: evidence from an objective performance paradigm

Object perception requires interpolation processes that connect visible regions despite spatial gaps. Some research has suggested that interpolation may be a 3-D process, but objective performance data and evidence about the conditions leading to interpolation are needed. The authors developed an objective performance paradigm for testing 3-D interpolation and tested a new theory of 3-D contour interpolation, termed 3-D relatability. The theory indicates for a given edge which orientations and positions of other edges in space may be connected to it by interpolation. Results of 5 experiments showed that processing of orientation relations in 3-D relatable displays was superior to processing in 3-D nonrelatable displays and that these effects depended on object formation. 3-D interpolation and 3-D relatabilty are discussed in terms of their implications for computational and neural models of object perception, which have typically been based on 2-D-orientation-sensitive units.