Brain morphological changes and functional neuroanatomy related to cognitive and emotional distractors during working memory maintenance in post-traumatic stress disorder

Post-traumatic stress disorder (PTSD) is associated with abnormalities in the processing and regulation of emotion as well as cognitive deficits. This study evaluated the differential brain activation patterns associated with cognitive and emotional distractors during working memory (WM) maintenance for human faces between patients with PTSD and healthy controls (HCs) and assessed the relationship between changes in the activation patterns by the opposing effects of distraction types and gray matter volume (GMV). Twenty-two patients with PTSD and twenty-two HCs underwent T1-weighted magnetic resonance imaging (MRI) and event-related functional MRI (fMRI), respectively. Event-related fMRI data were recorded while subjects performed a delayed-response WM task with human face and trauma-related distractors. Compared to the HCs, the patients with PTSD showed significantly reduced GMV of the inferior frontal gyrus (IFG) (p < 0.05, FWE-corrected). For the human face distractor trial, the patients showed significantly decreased activities in the superior frontal gyrus and IFG compared with HCs (p < 0.05, FWE-corrected). The patients showed lower accuracy scores and slower reaction times for the face recognition task with trauma-related distractors compared with HCs as well as significantly increased brain activity in the STG during the trauma-related distractor trial was observed (p < 0.05, FWE-corrected). Such differential brain activation patterns associated with the effects of distraction in PTSD patients may be linked to neural mechanisms associated with impairments in both cognitive control for confusable distractors and the ability to control emotional distraction.

Minimally Invasive Treatment of Inversion Shortening Calcaneal Fractures in the "Out-In" Position

OBJECTIVE

Heel fractures need extensive surgical incisions and are challenging to successfully reposition using traditional prying. The goal of this study is to evaluate the clinical effectiveness of using a Kirschner pin-guided distractor to treat inversion shortening calcaneal fractures in the "out-in" position.

METHODS

A total of 40 data from 37 patients with inversion shortened calcaneal fractures from January 2018 to March 2020 were reviewed. Preoperative lateral and axial X-rays and 3D CT were taken to assess the fracture type, and minimally invasive internal fixation was performed in the "out-in" position with distractor repositioning, and intraoperative and postoperative images were taken to assess fracture repositioning and fixation. During the follow-up period, the postoperative functional recovery status was assessed using the VAS score, AOFAS score, and FAOS score. Paired-samples t-test was used for all data comparisons.

RESULTS

All cases received a mean follow-up of 28.49 ± 3.25 months, and the mean fracture healing time was 7.84 ± 0.71 weeks. The postoperative images showed well-fixed fracture repositioning, and calcaneal height, length, width, and inversion angles were significantly improved. At the final follow-up, the calcaneal height, length, and width recovered from 39.35 ± 4.44mm, 79.35 ± 2.7mm, and 45.75 ± 2.87mm preoperatively to 50.93 ± 3.18mm, 82.23 ± 1.90mm, and 39.67 ± 1.58mm postoperatively (p < 0.001; p < 0.001; p < 0.001). The calcaneus inversion angle restored from 7.73° ± 2.26° to 3.80° ± 1.80° (p < 0.001). Böhler's angle and Gissane's angle improved from 13.13° ± 3.02° and 105.15° ± 8.94° to 27.95° ± 3.41° and 122.85° ± 5.54° (p < 0.001; p < 0.001). No non-healing fractures, osteomyelitis, or traumatic arthritis were observed.

CONCLUSION

Minimally invasive internal fixation with distractor repositioning in the "out-in" position is effective in the treatment of inversion shortening calcaneal fractures while restoring the anatomy and protecting the soft tissue.

Tuning to non-veridical features in attention and perceptual decision-making: An EEG study

When searching for a lost item, we tune attention to the known properties of the object. Previously, it was believed that attention is tuned to the veridical attributes of the search target (e.g., orange), or an attribute that is slightly shifted away from irrelevant features towards a value that can more optimally distinguish the target from the distractors (e.g., red-orange; optimal tuning). However, recent studies showed that attention is often tuned to the relative feature of the search target (e.g., redder), so that all items that match the relative features of the target equally attract attention (e.g., all redder items; relational account). Optimal tuning was shown to occur only at a later stage of identifying the target. However, the evidence for this division mainly relied on eye tracking studies that assessed the first eye movements. The present study tested whether this division can also be observed when the task is completed with covert attention and without moving the eyes. We used the N2pc in the EEG of participants to assess covert attention, and found comparable results: Attention was initially tuned to the relative colour of the target, as shown by a significantly larger N2pc to relatively matching distractors than a target-coloured distractor. However, in the response accuracies, a slightly shifted, "optimal" distractor interfered most strongly with target identification. These results confirm that early (covert) attention is tuned to the relative properties of an item, in line with the relational account, while later decision-making processes may be biased to optimal features.

A novel distractor-assisted reduction combined with the sinus tarsi approach for joint depression-type calcaneal fractures

PURPOSE

A novel percutaneous distractor with the advantage of axial and direct distraction was designed for the minimally invasive treatment of calcaneal fractures. The purpose of this study was to investigate the clinical results and complications of a novel distractor combined with sinus tarsi approach (STA) in treatment of the joint depression-type of calcaneal fractures.

METHODS

Fifty-four patients with the depression-type of calcaneal fractures (30 Sanders type II, 22 Sanders type III, 2 Sanders type IV) who were subjected to the novel distractor combined with STA were retrospectively assessed. Calcaneal height, width, and length; Bohler's angle; and the Gissane angle were evaluated pre-operatively and post-operatively. Clinical outcomes were assessed using the American Orthopedic Foot and Ankle Society (AOFAS) and visual analog scale (VAS) pain scores from the last follow-up. Complications were also recorded.

RESULTS

Fifty-two patients achieved an average follow-up of 24.3 months (range 18 to 34 months), and two patients were lost to follow-up six months post-operatively. There was significant difference between pre-operative and post-operative calcaneal height, width, and length; Bohler's angle; and Gissane angle (p < 0.01), but no significant difference was detected between the post-operative and normal side Bohler's angle (p > 0.05). The AOFAS ankle and hind foot score was 88.4 ± 6.6, and the VAS score was 1.9 ± 0.7 at the last follow-up. Nine (17.3%) patients developed complications: One experienced skin necrosis and two had screws loosening; three patients developed early degenerative changes of the subtalar joint; two had no symptoms; one had light pain around the subtalar joint without medical treatment; complex regional pain syndrome (CRPS) developed in one patient after seven months post-operatively; and two developed transient ankle stiffness.

CONCLUSION

The novel distractor combined with the STA effectively reconstructs the facet depression-type of calcaneal fractures (sanders type II and III) with minimal complications.

Role of reading medium and audio distractors on visual search

PURPOSE

Visual search is an active perceptual task influenced by objective factors and subjective factors such as task difficulty, distractors, attention and familiarity respectively. We studied the effect of different search directions, task medium and presence or absence of audio distractors on visual search time in young normal subjects METHODS: Twenty-four young (19-27 years) subjects with normal ocular health (except refractive error) participated in the study after obtaining informed consent. Subjects performed a word search task of ten 7-letter words of medium difficulty level. It was performed by each subject in Up-down, Down-Up, Left-Right, Right-Left, Diagonal and Random directions, with equal number of distractors. The task was performed in paper and digital medium, with or without audio distractors. The conditions were performed in random order by each subject and the time taken to accurately complete the word search was documented for each condition.

RESULT

The visual search time (VST) was significantly different with different search directions (ANOVA p<0.0001, df=5), considering both digital and non-digital medium, with or without audio distractors. The average VST was the least for left-right search direction (100±7.2 s) and was highest for random search direction (291±19 s), on a digital medium (VST_digital: 183±77 s) and in presence of an audio distractor (VST_audio: 184±77 s). The VST scores were not correlated with the age (r=-0.14, p = 0.25).

CONCLUSION

The visual search time is significantly delayed for search direction other than left-right direction and in presence of an audio distractor on a digital medium. These factors could play a significant role in visual orientation and specific tasks such as reading.

Multisensory integration and maternal sensitivity are related to each other and predictive of expressive vocabulary in 24-month-olds

Multisensory integration (MSI) is the ability to combine temporally synchronous, amodally specified sensory information to create rich, coordinated perceptual experiences. In early development, attention is directed toward such information in both social contexts (e.g., human speakers) and nonsocial contexts (e.g., multimodal toys). Parenting behaviors may support and sculpt multisensory integration by providing children with opportunities to experience amodally specified information (e.g., contingent face-to-face interactions). This study examined (a) whether 24-month-olds' MSI abilities differed as a function of context (social or nonsocial) and competition for attention (low or high), (b) whether MSI predicted expressive vocabulary, and (c) whether maternal sensitivity (MS) was related to both MSI and language. A total of 32 24-month-olds were tested in the Multisensory Attention Assessment Protocol, an audiovisual task that presents laterally positioned social/nonsocial events with and without a central distractor. Their mothers completed the MacArthur-Bates Communicative Development Inventories and participated in a free-play period with their children for MS coding. Results showed MSI in both social and nonsocial conditions (i.e., toddlers paid more attention to the "match"), but only the ability to maintain attention to the social match was related to toddlers' expressive vocabulary. In addition, MS was positively correlated with toddlers' expressive language and social MSI performance. Taken together, the pattern of results shows important relations between emerging integration abilities and parenting behavior as well as the ability of both factors to positively influence word learning during early toddlerhood.

Temporal expectancy modulates stimulus-response integration

We can use information derived from passing time to anticipate an upcoming event. If time before an event varies, responses towards this event become faster with increasing waiting time. This variable-foreperiod effect has been often observed in response-speed studies. Different action control frameworks assume that response and stimulus features are integrated into an event file that is retrieved later if features repeat. Yet the role of foreperiods has so far not been investigated in action control. Thus, we investigated the influence of foreperiod on the integration of action-perception features. Participants worked through a standard distractor-response binding paradigm where two consecutive responses are made towards target letters while distractor letters are present. Responses and/or distractors can repeat or change from first to second display, leading to partial repetition costs when only some features repeat or repetition benefits when all features repeat (the difference constituting distractor-response binding). To investigate the effect of foreperiod, we also introduced an anti-geometric distribution of foreperiods to the time interval before the first response display. We observed that distractor-response binding increased with increasing foreperiod duration, and speculate that this was driven by an increase in motor readiness induced by temporal expectancy.

Distracting tasks have persisting effects on young and older drivers' braking performance

It is well established that car driving performance suffers when the driver concurrently engages in a distracting activity, such as talking on a cell phone. The present study investigates whether the effects of driver distraction are short-lived, or rather persist for some time. Age-related differences are evaluated as well. Sixty-three young and 61 older adults were tested in a driving simulator. They were asked to follow a lead car that drove at a constant speed, and to concurrently engage in a pseudorandom sequence of distracting tasks (typing, reasoning, memorizing). When the lead car braked, participants had to brake as well to prevent a collision. The stimulus onset asynchrony between the braking task and the last preceding distraction was 11.49 ± 1.99 s. Each person was tested once in a multitasking condition (as described above), and once in a control condition without distracting tasks. Outcome measures quantified distance keeping and lane keeping while participants braked to the lead car. We found that braking responses differed significantly between conditions; this difference could be interpreted as a combination of performance deficits and compensatory strategies in the multitasking condition compared to the control condition. We also found significant differences between age groups, which could be interpreted similarly. Differences between age groups were less pronounced in the multitasking than in the control condition. All observed effects were associated with participants' executive functioning. Our findings confirm that distractions have an impact on braking responses, and they document for the first time that this impact can persist for about 11.5 s. We attribute this persistence to a task set effect, and discuss the practical relevance of our findings.

Neural mechanism for dynamic distractor processing during video target detection: Insights from time-varying networks in the cerebral cortex

In dynamic video target detection tasks, distractors may suddenly appear due to the dynamicity of the visual scene and the uncertainty of the visual information, strongly influencing participants' attention and target detection performance. Moreover, the neural mechanism that accounts for dynamic distractor processing remains unknown, which makes it difficult to compensate for in EEG-based video target detection. Here, cortical activities with high spatiotemporal resolution were reconstructed using the source localization method. The time-varying networks among important brain regions in different cognitive phases, including information integration, decision-making, and execution, were identified to investigate the neural mechanism of dynamic distractor processing. The experimental results indicated that dynamic distractors could induce a P3-like component. In addition, there was obvious asymmetry between the two hemispheres during video target detection. Specifically, the brain responses induced by dynamic distractors were weak and more concentrated in the left hemisphere during the information integration phase; left superior frontal gyrus activity related to preparation for the presence of distractors was critical, while the attention network and primary visual network, especially in the left visual pathway, were more active for dynamic targets during the decision-making phase. These findings provide guidance for designing an effective EEG-based model for dynamic video target detection.

Visual search asymmetry depends on target-distractor feature similarity: Is the asymmetry simply a result of distractor rejection speed?

Previous studies have shown that in visual search, varying the target and distractor familiarity produces a search asymmetry: Detecting a novel target among familiar distractors is more efficient than detecting a familiar target among novel distractors. One explanation is that novel targets have enhanced salience and are detected preattentively. Conversely, familiar distractors may be easier to reject. The current study postulates that target-distractor feature similarity, in addition to target or distractor familiarity, is a key determinant of visual search efficiency. The results of two experiments reveal that visual search is more efficient when distractors are familiar regardless of target familiarity, but only when the target-distractor similarity is high. When similarity is low, the visual search asymmetry disappears and the search times become highly efficient, with search slopes not different from zero regardless of target or distractor familiarity. However, although distractor familiarity plays an important role in inducing the search asymmetry, comparisons of search efficiency in target-present and target-absent trials reveal that search asymmetries cannot be explained solely by the faster speed of rejecting familiar distractors, as proposed by previous studies. Rather, distractor familiarity influences processes outside of stimulus selection, such as search monitoring and termination decisions. Competition among bottom-up item salience effects and top-down shape recognition processes is proposed to account for these findings.

Saccade accuracy as an indicator of the competition between functional asymmetries in vision

Hemispheric specialization refers to the fact that cerebral hemispheres are not equivalent and that cognitive processes are lateralized in the brain. Although the potential links between handedness and the left hemisphere specialization for language have been widely studied, little attention has been paid to other motor preferences, such as eye dominance, that also are lateralized in the brain. For example, saccadic accuracy is higher in the hemifield contralateral to the dominant eye compared to the ipsilateral hemifield. Saccade accuracy is, however, also known to be sensitive to other functional asymmetries, such as the lateralization of visuo-spatial attention in the right hemisphere of the brain. Using a global effect paradigm in three different saccade latency ranges, we here propose to use saccade accuracy as an indicator of visual functional asymmetries. We show that for the shortest latencies, saccade accuracy is higher in the left than in the right visual hemifield, which could be due to the lateralization of visuo-spatial attention in the right hemisphere. For the longest latencies, however, saccade accuracy is higher toward the right than the left hemifield, probably due to the lateralization of local and global processing in the left and right hemispheres, respectively. These results could have a major impact on studies designed to measure the degree of lateralization of individuals. We here discuss both the theoretical and clinical contributions of these results.

Minimally Invasive Plate Osteosynthesis Fracture Reduction Techniques in Small Animals

Indirect fracture reduction is used to align diaphyseal fractures when using minimally invasive fracture repair. Indirect reduction achieves functional fracture reduction without opening the fracture site. The limb is restored to length and spatial alignment is achieved to ensure proper angular and rotational alignment. Fracture reduction can be accomplished using a variety of techniques and devices, including hanging the limb, manual traction, distraction table, external fixators, and fracture distractors.

The effects of visual distractors on cognitive load in a motor imagery brain-computer interface

A brain-computer interface (BCI) is a system that translates neural activity into a practical output. Its functionality, therefore, depends not only on the computer itself, but also on the cognitive system of the user. Distractors have the potential to capture attention, increase cognitive load, and may therefore impact BCI use. The purpose of the current study is to determine the effects of small visual distractors on the cognitive load of users of a motor imagery-BCI, and to examine whether these distractor-mediated effects can be improved by modifying the task interface. Sixteen typically-developed participants completed two sessions of online motor imagery to control an EEG-BCI, under conditions of no distractors, visual distractors, and cognitive strategies (intended to mitigate cognitive load) amid distractors. Cognitive load for each session was assessed through both a ratio of theta to alpha power and the NASA-Task Load Index (NASA-TLX). Task-irrelevant visual stimuli were found to significantly increase the objective measure of cognitive load, particularly for parietal channels. Subjective cognitive load as indexed by the NASA-TLX was predictive of a decrease in BCI performance for participants with below 0.75 classification accuracy (R² = 0.32, p < 0.001), which may indicate a differential susceptibility to changes in workload for "low"-performing participants. Quantifying and addressing the increased cognitive load imparted by distractors on BCI users can aid in the future applicability of the technology in real-world settings.

Novel multi-axial alveolar distractor - Part I: Design, manufacture, and mechanical/functional tests

PURPOSE

This study developed a novel multi-axial alveolar distractor and evaluated its safety and effectiveness by performing various mechanical tests and finite element (FE) analysis.

MATERIALS AND METHODS

A ball-and-socket joint with a high degree of freedom was proposed as the design concept to make the distractor produce a cone trajectory motion range of up to 60° with respect to the transport screw (central axis). This device was manufactured with Ti6Al4V alloy. Mechanical functional tests included four-point bending resistance testing of the base bone plate, pull-out testing of the multi-axial alveolar distractor, welding strength testing between the base bone plate and ball-and-socket joint mechanism, and torque strength testing of the ball-and-socket joint. These tests were performed to ensure the effectiveness and safety of the multi-axial alveolar distractor. The base bone plate FE analysis of four-point bending resistance and pull-out testing of the multi-axial alveolar distractor were performed to confirm the results obtained from the experimental testing.

RESULTS

The bending strength for the four-point bending test and the maximum force for pull-out testing were 530.88 N mm and 716.33 N, respectively. Substantial equivalence FE simulations also found that large deformations for four-point bending and pull-out testing were smaller than those for the commercial alveolar distractor, indicating that our new distractor is as safe and effective as the commercially available device. The maximum debonding torque resistance for ball-and-socket joint mechanism welding strength was 3481.1 N mm, meaning it is unable to fall off during a surgical operation. No damage was found at the welding edge. The maximum average resistance force in the ball-and-socket joint was 30.26 N without rotation, allowing it to resist distraction forces during bone regeneration - an important safety consideration.

CONCLUSION

The alveolar distractor designed using a ball-and-socket joint concept can achieve multi-axial distraction with various angle adjustments in 3D space. Thorough mechanical/functional tests confirm the effectiveness and safety of our new multi-axial alveolar distractor.

Automatic distractor generation for multiple-choice English vocabulary questions

The use of automated systems in second-language learning could substantially reduce the workload of human teachers and test creators. This study proposes a novel method for automatically generating distractors for multiple-choice English vocabulary questions. The proposed method introduces new sources for collecting distractor candidates and utilises semantic similarity and collocation information when ranking the collected candidates. We evaluated the proposed method by administering the questions to real English learners. We further asked an expert to judge the quality of the distractors generated by the proposed method, a baseline method and humans. The results show that the proposed method produces fewer problematic distractors than the baseline method. Furthermore, the generated distractors have a quality that is comparable with that of human-made distractors.

Time course of inhibition of return in a spatial cueing paradigm with distractors

Studies of endogenous and exogenous attentional orienting in spatial cueing paradigms have been used to investigate inhibition of return, a behavioral phenomenon characterized by delayed reaction time in response to recently attended locations. When eye movements are suppressed, attention is covertly oriented to central or peripheral stimuli. Overt orienting, on the other hand, requires explicit eye movements to the stimuli. The present study examined the time course of slowed reaction times to previously attended locations when distractors are introduced into overt and covert orienting tasks. In a series of experiments, manual responses were required to targets following central and peripheral cues at three different cue-target intervals, with and without activated oculomotor systems. The results demonstrate that, when eye movements are suppressed, behavioral inhibition is reduced or delayed in magnitude by the presence of a distractor relative to conditions without distractors. However, the time course of behavioral inhibition when eye movements are required remains similar with or without distractors.

Development of a new three-directional distractor system for the correction of maxillary transverse and sagittal deficiency

PURPOSE

Class 3 malocclusions with maxillary deficiency, which are treated surgically and/or ordonotically, are common among adult patients. The aim of this study was to develop a three-directional bone-borne distractor that would allow the transverse expansion and sagittal advancement of the maxilla simultaneously.

MATERIALS AND METHODS

Computed tomography images of a patient with maxillary deficiency were transmitted to a software program, and a distractor was designed with different sizes (D1, D2, D3) and manufactured from titanium alloy. Y-shape segmental osteotomies were performed on the model, and vertical bite forces were applied. The biomechanical properties were evaluated by using the finite element method.

RESULTS

The highest von Mises stress value on the body of the distractor was seen in D2 (D2>D3>D1), with 234 N bite forces. D2 had maximum stress distribution on maxillary bone under 234 N and 93 N (D2>D1>D3). No difference was found among the plastic deformation rates according to biomechanical test results.

CONCLUSION

A three-directional bone-borne palatal distractor was produced, and this distractor system can be used for the treatment of skeletal class 3 patients with maxillary hypoplasia for its advantages of shortening the overall treatment time and reducing the scar formation. However, further animal and clinical studies are essential to determine the biological response of soft and hard tissues.

Now hear this: Inattentional deafness depends on task relatedness

Mixed results have been found for the impact of auditory information presented during high-perceptual-load visual search tasks, with some studies showing large effects and others indicating inattentional deafness, with such stimuli going largely undetected. In three experiments, we demonstrated that task relatedness is a key factor in whether extraneous auditory stimuli impact high-load visual searches. Experiment 1 addressed a methodological concern (e.g., Lavie Trends in Cognitive Sciences, 9, 75-82, 2005) regarding the timing of the relative onsets and offsets of task-related, to-be-ignored auditory stimuli and visual search arrays in experiments that have shown auditory distractor effects. Robust auditory distractor effects were found in each timing condition, and no inattentional deafness for high-load searches. Experiments 2 and 3 demonstrated that the relationship between the auditory stimuli and visual targets determined whether attention was captured and whether the response times to identify targets were impacted. Auditory stimuli that named a response-specific category influenced responses to targets mapped exclusively to one response, but not to the same targets mapped nonexclusively. These compatibility effects were larger if the distractors named an actual target item than if they named the category to which the item belonged. This pattern suggests that to-be-ignored auditory information that closely relates to a visual target search task influences the processing of that task, particularly in a high-perceptual-load search.

Does oxytocin lead to emotional interference during a working memory paradigm?

BACKGROUND

Oxytocin administration may increase attention to emotional information. We hypothesized that this augmented emotional processing might in turn lead to interference on concurrent cognitive tasks. To test this hypothesis, we examined whether oxytocin administration would lead to heightened emotional interference during a working memory paradigm. Additionally, moderating effects of childhood maltreatment were explored.

METHODS

Seventy-eight healthy males received 24 IU of intranasal oxytocin or placebo in a randomized placebo-controlled double-blind between-subjects study. A working memory task was performed during which neutral, positive, and negative distractors were presented.

RESULTS

The main outcome observed was that oxytocin did not enhance interference by emotional information during the working memory task. There was a non-significant trend for oxytocin to slow down performance irrespective of distractor valence, while accuracy was unaffected. Exploratory analyses showed that childhood maltreatment was related to lower overall accuracy, but in the placebo condition only. However, the maltreated group sample size was very small precluding any conclusions on its moderating effect.

CONCLUSIONS

Despite oxytocin's previously proposed role in enhanced emotional processing, no proof was found that this would lead to reduced performance on a concurrent cognitive task. The routes by which oxytocin exerts its effects on cognitive and social-emotional processes remain to be fully elucidated.

Effects of distractors on upright balance performance in school-aged children with attention deficit hyperactivity disorder, preliminary study

INTRODUCTION

Attention deficit hyperactivity disorder is a common impairing neuropsychiatric disorder with onset in early childhood. Almost half of the children with attention deficit hyperactivity disorder also experience a variety of motor-related dysfunctions ranging from fine/gross motor control problems to difficulties in maintaining balance.

OBJECTIVES

The main purpose of this study was to investigate the effects of distractors two different auditory distractors namely, relaxing music and white noise on upright balance performance in children with attention deficit hyperactivity disorder.

METHODS

We compared upright balance performance and the involvement of different sensory systems in the presence of auditory distractors between school-aged children with attention deficit hyperactivity disorder (n=26) and typically developing controls (n=20). Neurocom SMART Balance Master Dynamic Posturography device was used for the sensory organization test. Sensory organization test was repeated three times for each participant in three different test environments.

RESULTS

The balance scores in the silence environment were lower in the attention deficit hyperactivity disorder group but the differences were not statistically significant. In addition to lower balance scores the visual and vestibular ratios were also lower. Auditory distractors affected the general balance performance positively for both groups. More challenging conditions, using an unstable platform with distorted somatosensory signals were more affected. Relaxing music was more effective in the control group, and white noise was more effective in the attention deficit hyperactivity disorder group and the positive effects of white noise became more apparent in challenging conditions.

CONCLUSION

To the best of our knowledge, this is the first study evaluating balance performance in children with attention deficit hyperactivity disorder under the effects of auditory distractors. Although more studies are needed, our results indicate that auditory distractors may have enhancing effects on upright balance performance in children with attention deficit hyperactivity disorder.

A Comparative Study of Canine Retraction by Distraction of the Periodontal Ligament and Dentoalveolar Distraction Methods

INTRODUCTION

Canine distraction was introduced as an alternative treatment to retract the canines in minimum possible period of 3 weeks. It involved rapid canine retraction through distraction of the periodontal ligament. Another technique for rapid canine distalization involved osteotomies surrounding the canines to achieve rapid movement of the canines in the dentoalveolar segment known as dentoalveolar distraction. The present study is intended to assess and evaluate canine retraction by the above two mentioned methods of distraction osteogenesis.

MATERIALS AND METHODS

Eight orthodontic patients who required first premolar extractions were selected and 16 canines were distracted into the extraction space, using a distraction screw.

RESULTS

The distraction procedure was completed in 15.38 ± 1.51 days on the side of periodontal ligament distraction while it took 14.50 ± 2.45 days on the side of dentoalveolar distraction. No significant anchorage loss was seen in both the sides. The distal displacement of the canines was 6.63 ± 0.90 mm on the periodontal distraction side at the rate of 0.43 ± 0.05 mm/day and 6.91 ± 1.16 mm on the side of dentoalveolar distraction at the rate of 0.48 ± 0.08 mm/day. An angulation change of 14.94° ± 7.58° was observed in canine inclination in periodontal distraction side while change of 14.88° ± 3.15° was seen in the dentoalveolar distraction side.

CONCLUSION

No significant differences in the various parameters were found between both the techniques of canine retraction by distraction osteogenesis, while reducing orthodontic treatment duration by 6-9 months without any unfavorable short-term effects on the periodontium.

The temporal dynamics of the distractor in the global effect

In the global effect, saccades are displaced towards a distractor if the latter is near to the target, an effect thought to reflect spatial averaging in neurons of the superior colliculus. The temporal dynamics of the global effect have not been well studied, however. We had twelve subjects perform horizontal saccades to a target in trials in which there were either no distractor or a distractor stimulus located 20° above or below the target. The distractor appeared either simultaneously with the target or preceded it by an interval of between 100 and 800 ms, and was either flashed for only 100 ms or remained visible until the subject responded with a saccade. Both flashed and persistent distractors reduced saccadic latency if they preceded target onset, indicating that subjects could use this cue to prepare saccades in advance. Saccadic endpoint was displaced towards a flashed distractor only if it was simultaneous with the target. However, persistent distractors produced a global effect for both simultaneous presentation and distractor-target intervals of 100 ms, but not for longer intervals. We conclude that the global effect requires of the distractor both a recent onset and persistence of the distractor, and that distractor-related activity decays rapidly within 300 ms.

Potentiation rather than distraction in a trace fear conditioning procedure

Trace conditioning procedures are defined by the introduction of a trace interval between conditioned stimulus (CS, e.g. noise or light) offset and unconditioned stimulus (US, e.g. footshock). The introduction of an additional stimulus as a distractor has been suggested to increase the attentional demands of the task and to extend the usefulness of the behavioural model. In Experiment 1, the CS was noise and the distractor was provided by an intermittent light. In Experiment 2, the CS was light and the distractor was provided by an intermittent noise. In both experiments, the introduction of a 10s trace interval weakened associative learning compared with that seen in a 0s delay conditioned group. However, there was no consistent evidence of distraction. On the contrary, in Experiment 1, associative learning was stronger (in both trace and delay conditioned groups) for rats conditioned also in the presence of the intermittent light. In Experiment 2, there was no such effect when the roles of the stimuli were reversed. The results of Experiment 2 did however confirm the particular salience of the noise stimulus. The finding of increased associative learning dependent on salience is consistent with arousal-mediated effects on associative learning.

Visual illusion and line bisection: a bias hypothesis revisited

It is generally accepted that visual illusions affect line bisection in the predicted direction. However, it has been reported an illusionary bias which seems questioning such general view. In a previous study, participants bisected lines flanked at both ends by two pairs of arrows, pointing in the same direction. The medialmost vertices of one pair converged on the line (converging arrows), whereas those of the other pair did not (non-converging arrows). Participants bisected lines toward the base of the arrows, i.e., toward the wider end of the stimulus and in the direction opposite to that predicted by the Baldwin illusion. However, the bisection bias was also directed away from the location of the converging arrows. We investigated what is the main factor affecting line bisection: arrows orientation, as previously suggested, or interference effects related to the location of converging arrows. In experiment 1, participants bisected lines flanked by converging versus non-converging arrows. Results confirmed the presence of a bisection bias directed not only toward the base of the converging arrows but also away from their location. In experiment 2, the arrows were located more internally, so that their medialmost vertices always converged on the line. Results showed that the bisection bias was directed away from the location of the arrows regardless of their orientation. It is suggested that the previously reported bisection bias did not depend on arrows orientation, but rather on interference effects related to converging arrows position. The theoretical implications of the results are discussed.

The Effect of Using a Modified Dentoalveolar Distractor on Canine Angulation following Rapid Canine Retraction: A Split-mouth Design Randomized Controlled Trial

BACKGROUND AND OBJECTIVES

New studies have been published and aimed to retract canines by means of distraction osteogenesis to reduce treatment time. Although a great care has been given to achieve a bodily movement of the canines, a significant amount of tipping of the canines has been observed. This trial aimed to assess the effect of applying a modified distractor on canine angulation.

MATERIALS AND METHODS

The sample of the study consisted of 14 canines in seven patients (16-25 years). After the osteotomy procedure, two distractors were applied (one distractor on each side). After 5 days of a latency period, the two distractors were activated at a rate of 1 mm/day.

RESULTS

There was a significant difference between the two distractors regarding the time required to retract the canines (p = 0.008) and the observed change in canine angulation following retraction (p = 0.028). The change in the overjet and the mandibular plane angle was statistically insignificant. Eight out of 14 distracted canines reacted positively to the pulp vitality tester after 3 months of completion of distraction. There was no clinical sign of discoloration or pulpal pain in any canine.

CONCLUSION

Within the limits of this study, the modified distractor caused a bodily movement of the canine with a minimal tipping. Further research is required on a long-term basis on a larger group of patients to gain more insight on the observed changes.

Methylphenidate alters selective attention by amplifying salience

RATIONALE

Methylphenidate, the most common treatment of attention deficit hyperactivity disorder (ADHD), is increasingly used by healthy individuals as a "smart drug" to enhance cognitive abilities like attention. A key feature of (selective) attention is the ability to ignore irrelevant but salient information in the environment (distractors). Although crucial for cognitive performance, until now, it is not known how the use of methylphenidate affects resistance to attentional capture by distractors.

OBJECTIVES

The present study aims to clarify how methylphenidate affects distractor suppression in healthy individuals.

METHODS

The effect of methylphenidate (20 mg) on distractor suppression was assessed in healthy subjects (N = 20), in a within-subject double-blind placebo-controlled crossover design. We used a visuospatial attention task with target faces flanked by strong (faces) or weak distractors (scrambled faces).

RESULTS

Methylphenidate increased accuracy on trials that required gender identification of target face stimuli (methylphenidate 88.9 ± 1.4 [mean ± SEM], placebo 86.0 ± 1.2 %; p = .003), suggesting increased processing of the faces. At the same time, however, methylphenidate increased reaction time when the target face was flanked by a face distractor relative to a scrambled face distractor (methylphenidate 34.9 ± 3.73, placebo 26.7 ± 2.84 ms; p = .027), suggesting enhanced attentional capture by distractors with task-relevant features.

CONCLUSIONS

We conclude that methylphenidate amplifies salience of task-relevant information at the level of the stimulus category. This leads to enhanced processing of the target (faces) but also increased attentional capture by distractors drawn from the same category as the target.