Improvement In Task Accuracy Research Articles

Changes in brain perfusion with training-related visuomotor improvement in MS.

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system. A better understanding of the mechanisms supporting brain plasticity in MS would help to develop targeted interventions to promote recovery. A total of 29 MS patients and 19 healthy volunteers underwent clinical assessment and multi-modal MRI acquisition [fMRI during serial reaction time task (SRT), DWI, T1w structural scans and ASL of resting perfusion] at baseline and after 4-weeks of SRT training. Reduction of functional hyperactivation was observed in MS patients following the training, shown by the stronger reduction of the BOLD response during task execution compared to healthy volunteers. The functional reorganization was accompanied by a positive correlation between improvements in task accuracy and the change in resting perfusion after 4 weeks' training in right angular and supramarginal gyri in MS patients. No longitudinal changes in WM and GM measures and no correlation between task performance improvements and brain structure were observed in MS patients. Our results highlight a potential role for CBF as an early marker of plasticity, in terms of functional (cortical reorganization) and behavioral (performance improvement) changes in MS patients that may help to guide future interventions that exploit preserved plasticity mechanisms.

Semi-Supervised 3D Medical Image Segmentation Based on Dual-Task Consistent Joint Learning and Task-Level Regularization.

Semi-supervised learning has attracted wide attention from many researchers since its ability to utilize a few data with labels and relatively more data without labels to learn information. Some existing semi-supervised methods for medical image segmentation enforce the regularization of training by implicitly perturbing data or networks to perform the consistency. Most consistency regularization methods focus on data level or network structure level, and rarely of them focus on the task level. It may not directly lead to an improvement in task accuracy. To overcome the problem, this work proposes a semi-supervised dual-task consistent joint learning framework with task-level regularization for 3D medical image segmentation. Two branches are utilized to simultaneously predict the segmented and signed distance maps, and they can learn useful information from each other by constructing a consistency loss function between the two tasks. The segmentation branch learns rich information from both labeled and unlabeled data to strengthen the constraints on the geometric structure of the target. Experimental results on two benchmark datasets show that the proposed method can achieve better performance compared with other state-of-the-art works. It illustrates our method improves segmentation performance by utilizing unlabeled data and consistent regularization.

Neural correlates of learning in a linear discriminant analysis brain-computer interface paradigm

Objective. With practice, the control of brain-computer interfaces (BCI) would improve over time; the neural correlate for such learning had not been well studied. We demonstrated here that monkeys controlling a motor BCI using a linear discriminant analysis (LDA) decoder could learn to make the firing patterns of the recorded neurons more distinct over a short period of time for different output classes to improve task performance. Approach. Using an LDA decoder, we studied two Macaque monkeys implanted with microelectrode arrays as they controlled the movement of a mobile robotic platform. The LDA decoder mapped high-dimensional neuronal firing patterns linearly onto a lower-dimensional linear discriminant (LD) space, and we studied the changes in the spatial coordinates of these neural signals in the LD space over time, and their correspondence to trial performance. Direction selectivity was quantified with permutation feature importance (FI). Main results. We observed that, within individual sessions, there was a tendency for the points in the LD space encoding different directions to diverge, leading to fewer misclassification errors, and, hence, improvement in task accuracy. Accuracy was correlated with the presence of channels with strong directional preference (i.e. high FI), as well as a varied population code (i.e. high variance in FI distribution). Significance. We emphasized the importance of studying the short-term/intra-sessional variations in neural representations during the use of BCI. Over the course of individual sessions, both monkeys could modulate their neural activities to create increasingly distinct neural representations.

Proximal Upper Limb Sensorimotor Integration in Response to Novel Motor Skill Acquisition.

Previous studies have shown significant changes in cortical and subcortical evoked potential activity levels in response to motor training with the distal upper-limb muscles. However, no studies to date have assessed the neurological processing changes in somatosensory evoked potentials (SEPs) associated with motor training whole-arm movements utilizing proximal upper-limb muscles. The proximal upper-limb muscles are a common source of work-related injuries, due to repetitive glenohumeral movements. Measuring neurophysiological changes following performance of a proximal motor task provide insight into potential neurophysiological changes associated with occupational postures and movements involving proximal upper limb muscles. This study sought to assess the impact of a novel motor skill acquisition task on neural processing of the proximal upper-limb muscle groups, through the measurement of short-latency median nerve SEPs. One group of 12 participants completed a novel motor training task, consisting of tracing a sinusoidal waveform varying in amplitude and frequency. Baseline SEP measurements were recorded from each participant, followed by a mental recitation control task. Pre-test SEP measurements were then recorded, followed by the motor training task, and post-test SEP recordings. The participants completed the tracing with their right thumb, using glenohumeral rotation only to move their hand. Significant improvements in task accuracy were demonstrated, indicating that motor acquisition had occurred. Significant changes were also seen in the N11, N13, N20, N24, P25, and the N30 SEP peaks were seen following the motor training task. Conclusion: Early SEPs appear to be a sensitive measure of changes in sensorimotor integration in response to novel motor skill acquisition within the proximal upper-limb muscles.

Longitudinal fMRI task reveals neural plasticity in default mode network with disrupted executive-default coupling and selective attention after traumatic brain injury.

Executive dysfunctions are common in individuals with Traumatic Brain Injury (TBI). However, change in functional neural coupling of default and executive networks in the post-acute phase (≥ 1month after injury) patients over time has yet to be understood. During a 5-week observation period, we examined changes in the goal-oriented executive function networks in 20 TBI participants, using a face/scene matching 1-back fMRI task (Chen et al. 2011). We conducted multivariate pattern analysis to assess working memory and visual selective attention, followed by a repeat-measures ANOVA to examine longitudinal changes, with a cluster FDR at p = .001. Results showed that task accuracy significantly improved after follow-up. Significantly increased activity patterns over time were observed in the right dorsolateral prefrontal cortex and right insula. Decreased activity patterns were seen in the left posterior cingulate cortex (PCC), bilateral precuneus, right inferior occipital gyrus and right temporo-occipital junction. Improvement in task accuracy correlated with decreased activity patterns in the PCC (r = -0.478, p = 0.031) and temporo-occipital junction (r = -0.592, p = 0.006), which were interpreted as neural plastic changes. However, we did not observe the default mode network (DMN)-executive network decoupling during task performance that is found in other studies. These results suggest that fMRI of attentional task performance could serve as a potential biomarker for neural plasticity of selective attention in TBI patients in the post-acute phase.

Effect of Prefrontal Cortex Stimulation on Regulation of Amygdala Response to Threat in Individuals With Trait Anxiety

Transcranial direct current stimulation (tDCS) of the dorsolateral prefrontal cortex (DLPFC) is under clinical investigation as a treatment for major depressive disorder. However, the mechanisms of action are unclear, and there is a lack of neuroimaging evidence, particularly among individuals with affective dysfunction. Furthermore, there is no direct causal evidence among humans that the prefrontal-amygdala circuit functions as described in animal models (ie, that increasing activity in prefrontal cortical control regions inhibits amygdala response to threat). To determine whether stimulation of the prefrontal cortex reduces amygdala threat reactivity in individuals with trait anxiety. This community-based randomized clinical trial used a double-blind, within-participants design (2 imaging sessions per participant). Eighteen women with high trait anxiety (age range, 18-42 years) who scored greater than 45 on the trait measure of State-Trait Anxiety Inventory were randomized to receive active or sham tDCS of the DLPFC during the first session and the other intervention during the next session. Each intervention was followed immediately by a functional imaging scan during which participants performed an attentional task requiring them to ignore threatening face distractors. Data were collected from May 7 to October 6, 2015. Amygdala threat response, measured with functional magnetic resonance imaging. Data from 16 female participants (mean age, 23 years; range, 18-42 years), with 8 in each group, were analyzed. Compared with sham stimulation, active DLPFC stimulation significantly reduced bilateral amygdala threat reactivity (z = 3.30, P = .04) and simultaneously increased activity in cortical regions associated with attentional control (z = 3.28, P < .001). In confirmatory behavioral analyses, there was a mean improvement in task accuracy of 12.2% (95% CI, 0.30%-24.0%; mean [SD] difference in number of correct answers, 2.2 [4.5]; t15 = 1.94, P = .04) after active DLPFC stimulation. These results reveal a causal role for prefrontal regulation of amygdala function in attentional capture by threat in individuals with high trait anxiety. The finding that prefrontal stimulation acutely increases attentional control signals and reduces amygdala threat reactivity may indicate a neurocognitive mechanism that could contribute to tDCS treatment effects in affective disorders. isrctn.org Identifier: ISRCTN78638425.

A Study on the Effect of Traceability Links in Software Maintenance

In software development, stakeholders of the same project often collaborate asynchronously through shared artifacts. A traceability system links a project's artifacts and therefore provides support for collaboration among stakeholders. Different stakeholders are interested in different types of traceability links. The literature often states that traceability is useful but expensive to build and maintain. However, there is no study showing reduction in effort when traceability links among various software artifacts are provided and used during the maintenance phase. This paper presents a study evaluating the benefits of using traceability among requirements, design, code, code inspections, builds, defects, and tests artifacts in the maintenance phase. Before the study, a survey was conducted at a large industrial firm to determine the type of links that different stakeholders are interested in. Twenty-five stakeholders from this firm participated in a survey to define the type of traceability links that were of interest to them. With this result, a traceability link model is proposed that categorizes different types of traceability links based on stakeholders' roles. This link model was used in the study. Twenty-eight subjects from industry and academia participated in the empirical study that was conducted after the survey. A prototype link-tracing tool, TraceLink, was developed and used in the study to present traceability links to the experimental group, whereas the control group was not given any links to solve the tasks. Five maintenance tasks were used in the study. The results show a significant improvement in task accuracy (86.06%) when traceability links were given to the subjects. In conclusion, a traceability model based on an industrial survey provided traceability views that are based on stakeholders' roles. This empirical study provides evidence that traceability links are effective in solving maintenance tasks with higher accuracy.

Neural indicators of error processing and intraindividual variability in reaction time in 7 and 9 year‐olds

Childhood is associated with improvements in task accuracy, response time, and reductions in intraindividual trial-to-trial variability in reaction times. The aims of this study were to investigate neural indicators of error monitoring to better understand the mechanisms underlying these cognitive developments in primary school aged children. Specifically, this study explored the development of error processing in 36 children aged 7 years and 41 children aged 9 years, as indexed by two electrophysiological indices of error processing, the error-related negativity (ERN) and the error positivity (Pe). Notably, the amplitude and latency of the ERN and Pe did not differ significantly between the age groups. However, intraindividual variability in response time (RT) was strongly related to ERN amplitude. These data suggest the utility of comparing neural and behavioral indicators of cognitive performance in children and uniquely highlight the importance of considering intraindividual variability in task performance in studies that explore error processing.

Top-Down modulation of neural responses in visual perception: a computational exploration

Visual perception is typically performed in the context of a task or goal. Nonetheless, visual processing has traditionally been conceptualized in terms of a fixed, task-independent hierarchy of feature detectors. We explore the computational implications of allowing early visual processing to be task modulated. Using artificial neural networks, we show that significant improvements in task accuracy can be obtained by allowing the weights to be modulated by task. The primary benefits are obtained under resource-limited processing. A relatively modest task-based modulation of weights and activities can lead to a large performance boost, suggesting an efficient means of increasing effective cortical capacity.

Neural correlates of adjunctive rivastigmine treatment to antipsychotics in schizophrenia: A randomized, placebo-controlled, double-blind fMRI study

Facilitation of central cholinergic activity may form a potential treatment strategy for cognitive impairment in schizophrenia. In a randomized, placebo-controlled, double-blind, parallel-group design, we investigated the neural correlates of cognitive effects of rivastigmine, an acetylcholinesterase inhibitor, given as an add-on therapy to antipsychotic-treated schizophrenia patients. Thirty-six chronic schizophrenia patients with mild cognitive impairment took part. After 1 week on placebo (baseline), all patients entered a double-blind protocol; 18 were allocated to receive rivastigmine and 18 placebo for the next 12 weeks (final sample with usable imaging data: 11 patients on rivastigmine, 10 on placebo). All patients underwent functional magnetic resonance imaging during a parametric ‘ n-back’ task, involving monitoring of dots in particular locations on a screen at a given delay from the original occurrence, twice: at baseline and 12 weeks post-rivastigmine/placebo treatment. Compared to placebo, rivastigmine produced only a small and non-significant improvement in task accuracy across all conditions with no change in response latency, and increased activity in the extrastriate visual cortex in areas associated with visual and spatial attention but not in any region within the working memory network. Our observations suggest that cholinergic enhancement with rivastigmine at doses known to be effective in Alzheimer's disease does not produce strong and clinically meaningful cognitive and neural changes in schizophrenia patients treated with atypical antipsychotics although the neural effects in terms of enhanced neuronal activity in regions associated with visual and spatial attention are consistent with those reported previously with cholinergic enhancement in healthy subjects.

Donepezil-induced improvement in delayed matching accuracy by young and old rhesus monkeys.

Donepezil (Aricept), a long-acting cholinesterase inhibitor, is widely used in the treatment of Alzheimer's disease to improve cognition and memory. Many drugs within the class of cognition-enhancing agents, both currently approved medications and those under development, have clinical indications narrowly relegated to Alzheimer's disease. The purpose of this study was to determine whether the efficacy attributed to donepezil in its ability to improve delayed matching accuracy by monkeys was independent of age. Male and female rhesus monkeys (n = 17) ranging from 9to 29 yr of age were administered donepezil (10, 25, 50, and 100 microg/kg, im) during 4 discrete test days. Donepezil treatment improved average task accuracy, but intersubject variability prohibited statistical significance. When animals were considered individually, the most effective dose of donepezil was associated with a highly significant increase in group task performance that was consistent with enhanced recall during testing. The variability associated with the dose-response analysis was attributable primarily to subject age, such that older monkeys required higher doses of donepezil. Yet at doses that were effective in all subjects, there was no relationship between age and the improvement in task accuracy. Likewise, there was no association between baseline task proficiency and improvement in task accuracy.

Enhanced attention in rhesus monkeys as a common factor for the cognitive effects of drugs with abuse potential.

One of the common neurochemical features of many drugs of abuse is their ability to directly or indirectly enhance dopaminergic activity in the brain, particularly within the ventral tegmental-nucleus accumbens pathway. Dopaminergic pathways in the frontal and limbic cortex also may be targets for these agents, where pharmacological effects could result in heightened attention and/or support self-administration behavior. The purpose of this study was to determine whether drugs from differing pharmacological classes that exhibit abuse potential would share the ability to counter distractability in the delayed matching task. Well trained mature macaques performed a computer-assisted delayed matching-to-sample task which included trials associated with three delay intervals and randomly interspersed task-relevant distractors. Drug regimens included four to five doses and subjects were tested no more than twice per week. All but one of the six compounds (tomoxetine), on average, increased task accuracy for either non-distractor or distractor trials. It was evident that for several compounds, doses required to improve accuracy for non-distractor trials were routinely greater than the doses required to improve accuracy for distractor trials. Data for the individualized Best dose (based upon the subject's optimal level of accuracy during distractor trials) revealed statistically significant distractor-related improvements in task accuracy for the same five compounds. The relative efficacy for reversing distractor-induced decrements in task accuracy was estimated by the level of improvement with respect to baseline: nomifensine (31%)>nicotine (22%) approximately morphine (19%) approximately caffeine (19%) approximately methylphenidate (22%) >tomoxetine (9%). Tomoxetine (noradrenergic preferring) was the only compound that did not produce a significant improvement in accuracy. These results provide pharmacological support for the concept that attentional mechanisms may play an important role in the "environmental" associative aspects of drug seeking behavior, and as such they may provide the basis for treatment strategies aimed at preventing relapse in detoxified addicts.

Sex dimorphisms in the cognitive-enhancing action of the Alzheimer’s drug donepezil in aged Rhesus monkeys

Brain acetylcholinesterase has been targeted for the development of novel treatments for memory deficits associated with Alzheimer’s disease (AD) and other neurodegenerative disorders. The long-acting AChE inhibitor donepezil (Aricept™) is used to improve memory and other aspects of cognition in AD patients. Because donepezil and other cholinesterase inhibitors are effective in a restricted population of AD patients, this study was to designed to determine whether aged females monkeys receive the same level of benefit to the mnemonic action of donepezil as do males. In this study, six male and six female rhesus monkeys (>20 years) who were proficient in the performance of a delayed matching-to-sample task each received an ascending series of four doses of donepezil (0.01–0.1 mg/kg) over 5 weeks. As a group, male subjects exhibited improvement in task accuracy across the three highest doses, with the maximum effect occurring after the 0.025 mg/kg dose. However, the females exhibited increased task accuracy only after the highest dose. When data were combined for sessions run 10 min after drug administration and for sessions run 24 h later (in the absence of drug), improvements in task accuracy were greater on average for males. Most of this difference was attributed to the fact that task accuracy by females actually declined during sessions run after the two lowest doses of donepezil. When task performance after donepezil was determined as the individualized Best Dose, as a group, males responded maximally to less than half the dose that was maximal for females. These findings support the concept that aged males and females respond differently to this class of agents, perhaps representing fundamental sex-related differences in memory processing, or in the manner that age affects these processes.

Post-Stroke Rehabilitation with the Rutgers Ankle System: A Case Study

The “Rutgers Ankle” is a Stewart platform-type haptic interface designed for use in rehabilitation. The system supplies six-degree-of-freedom (DOF) resistive forces on the patient's foot, in response to virtual reality-based exercises. The Rutgers Ankle controller contains an embedded Pentium board, pneumatic solenoid valves, valve controllers, and associated signal conditioning electronics. The rehabilitation exercise used in our case study consists of piloting a virtual airplane through loops. The exercise difficulty can be selected based on the number and placement of loops, the airplane speed in the virtual environment, and the degree of resistance provided by the haptic interface. Exercise data is stored transparently, in real time, in an Oracle database. These data consist of ankle position, forces, and mechanical work during an exercise, and over subsequent rehabilitation sessions. The number of loops completed and the time it took to do that are also stored online. A case study is presented of a patient nine months post-stroke using this system. Results showed that, over six rehabilitation sessions, the patient improved on clinical measures of strength and endurance, which corresponded well with torque and power output increases measured by the Rutgers Ankle. There were also substantial improvements in task accuracy and coordination during the simulation and the patient's walking and stair-climbing ability.