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Background: Transcranial static magnetic stimulation (tSMS) is a non-invasive brain stimulation technique that place a strong neodymium magnet on scalp to reduce cortical excitability. We have recently developed a new tSMS device with three magnets placed close to each other (triple tSMS) and confirmed that this new device can produce a stronger and broader static magnetic field than the conventional single tSMS. The aim of the present study was to investigate the effect of the conventional single tSMS as well as triple tSMS over the unilateral or bilateral motor association cortex (MAC) on simple and choice reaction time (SRT and CRT) task performance. Methods: There were two experiments: one involved the conventional tSMS, and the other involved the triple tSMS. In both experiments, right-handed healthy participants received each of the following stimulations for 20 min on different days: tSMS over the unilateral (left) MAC, tSMS over the bilateral MAC, and sham stimulation. The center of the stimulation device was set at the premotor cortex. The participants performed SRT and CRT tasks before, immediately after, and 15 min after the stimulation (Pre, Post 0, and Post 15). We evaluated RT, standard deviation (SD) of RT, and accuracy (error rate). Simulation was also performed to determine the spatial distribution of magnetic field induced by tSMS over the bilateral MAC. Results: The spatial distribution of induced magnetic field was centered around the PMd for both tSMS systems, and the magnetic field reached multiple regions of the MAC as well as the sensorimotor cortices for triple tSMS. SD of CRT was significantly larger at Post 0 as compared to Pre when triple tSMS was applied to the bilateral MAC. No significant findings were noted for the other conditions or variables. Discussion: We found that single tSMS over the unilateral or bilateral MAC did not affect performance of RT tasks, whereas triple tSMS over the bilateral MAC but not over the unilateral MAC increased variability of CRT. Our finding suggests that RT task performance can be modulated using triple tSMS.

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There is a need for objective, easy and relatively short methods to diagnose cognition in depression. We have constructed a set of simple visual tasks using three different ways of speed measuring: paper-pencil-based, computer-based, and eye-tracking based. We used a single case design with 22 participants. A clinical group counted 11 patients with major depression examined two times (first examination without medication and second after three months of medical treatment) together with a group of 11 matched healthy controls. Cognitive difficulties were observable in all the checked levels of performance. The weakest in all tasks were patients before medication, some improvement was observed after medical treatment, but not matching the level of healthy controls. Cognitive difficulties were not eliminated by medical treatment as quickly as emotional disturbances were. The observed difficulties could be interpreted in terms of psychomotor retardation, a typical symptom in depression, which proved to be mainly cognitive as the analysis of differences in reaction times and the first saccade latencies concluded. The analysis of simple visual reaction times on several stages turned out to be a promising method to measure the cognitive state in persons with mood disorders and cognitive convalescence during major depressive disorder treatment.

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Cyclic glycyl-proline (cGP) exerts neuroprotective effects against ischemic stroke and may promote neural plasticity or network remodeling. We sought to determine to what extent oral administration of cGP could facilitate task learning in rats with ischemic lesions. We trained rats to perform a choice reaction time task using their forepaws. One week after changing the food to pellets containing cGP (no cGP: 0 mg/kg; low cGP: 25 mg/kg; and high cGP: 75 mg/kg), we made a focal ischemic lesion on the left or right forepaw area of the sensorimotor cortex. After recovery of task performance, we altered the correct-response side of the task, and then analyzed the number of training days required for the rat to reach a learning criterion (error rate < 15%) and the regulation of adult neurogenesis in the subventricular zones (SVZs), taking lesion size into account. The low-cGP group required fewer training days for task learning than the no-cGP group. Unexpectedly, rats with larger lesions required fewer training days in the no-cGP and low-cGP groups, but more training days in the high-cGP group. The number of Ki67-immunopositive cells (indicating proliferative cells) in ipsilesional SVZ increased more rapidly in the low-cGP and high-cGP groups than in the no-cGP group. However, lesion size had only a small effect on required training days and the number of Ki67-immunopositive cells. We conclude that oral administration of cGP can facilitate task learning in rats with focal ischemic infarction through neural plasticity and network remodeling, even with minimal neuroprotective effects.

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BACKGROUND: Gait initiation is an automatized motor program that is preceded by anticipatory postural adjustments (APAs). During attentional tasks, these APAs can be modulated, producing multiple APAs. However, the role of the peripheral nervous system in the regulation of these APAs is unknown. RESEARCH QUESTION: The objective of our study was to investigate whether APAs are also regulated by peripheral nervous afferents. METHODS: We assessed 21 patients suffering from chronic inflammatory demyelinating neuropathy and 20 healthy controls. Participants initiated gait with the right or left leg either freely (in the standard condition) or according to a visual trigger (i.e., the select condition). Kinetic and kinematic parameters of APAs and step initiation were recorded. RESULTS: The select condition was related to a higher rate of multiple APAs compared to the standard condition, and was more attention-consuming in both groups. The group with a neuropathy showed longer APAs than the control group, associated with a longer time to recover from multiple APAs. Consequently, the step execution time was delayed in patients with a peripheral neuropathy. SIGNIFICANCE: The impairment of the peripheral nervous system is therefore responsible for an alteration of the mechanisms underlying the recovery from multiple APAs during gait initiation. Our results are in favor of a role of proprioceptive afferents in the early peripheral regulation of motor errors. Further study on gait initiation in peripheral nervous disease could be helpful to better explore sensory-motor coupling in tasks requiring balance control.

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The adverse effects of depression on patients' life have been reported but information about its effects on the sequential organization of the information processing stages remains poorly understood as previous studies focused only on distinct stages. This study adds to existing knowledge by examining the effect of major depressive disorder (MDD) on the sequential organization of information processing, executive and community functioning. Fifty-seven participants with 19 participants each for first episode depression (FMDD), recurrent episodes depression (RMDD), and healthy controls (HCs) participated in this study. They completed assessments on executive and community functioning measures, and choice reaction time task (CRTT) for the event-related potential (ERP) data. Findings revealed no significant between-group difference in executive functioning but participants with depression (FMDD and RMDD) were found to be more depressed, with FMDD participants having worse community functioning skills compared with HCs. There was no significant between-group main effect on behavioral data. ERP data showed significantly less positive-going P3b among RMDD participants compared with HCs. FMDD participants used a different information processing strategy at P1, while HCs and RMDD participants used a different processing strategy at N2b compared with the other group(s), respectively. The results suggest the use of multifaceted assessment to get a holistic view of the health status of people with MDD in order to inform clinicians on the appropriate interventional strategies needed for the patient.

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In sentences with a complex subject noun phrase, like "The key to the cabinets is lost", the grammatical number of the head noun (key) may be the same or different from that of the modifier noun phrase (cabinets). When the number is the same, comprehension is usually easier than when it is different. Grammatical number computation may occur while processing the modifier noun (integration phase) or while processing the verb (checking phase). We investigated at which phase number conflict and plausibility of the modifier noun as subject for the verb affect processing, and we imposed a gaze-contingent tone discrimination task in either phase to test whether number computation involves executive control. At both phases, gaze durations were longer when a concurrent tone task was present. Additionally, at the integration phase, gaze durations were longer under number conflict, and this effect was enhanced by the presence of a tone task, whereas no effects of plausibility of the modifier were observed. The finding that the effect of number match was larger under load shows that computation of the grammatical number of the complex noun phrase requires executive control in the integration phase, but not in the checking phase.

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PURPOSE: To assess cognitive performance differences pre- and post-exercise in individuals without concussion (non-concussed, NC) and individuals with post-concussion syndrome (PCS). METHODS: A total of 30 participants completed a choice reaction time (CRT) task in the form of an iPad application, measuring each individual's decision-making capabilities, while wearing a head-mounted eye tracker system. Participants completed four blocks of testing; the time interval between the first two blocks of trials and the last two blocks of trials was 10 minutes. Between the completion of block 2 and the start of block 3, the participants completed a 15-minute bout of exercise. RESULTS: Individuals with PCS at rest and following exercise displayed greater average reaction time (RT) (p<.01), lower overall accuracy (p<.01) and shorter final fixation durations (p<.05) than NC. Combined influence of learning and exercise resulted in a significant difference (p<.05) in RT from block 1 to block 3 and block 1 to block 4. CONCLUSION: Persistent concussion-based symptoms may be indicative of deficits in higher-level cognitive processing, as indicated by both decreased CRT performance and differences in gaze behaviours between groups. Therefore, individuals with PCS may not elicit appropriate decisions when navigating through an environment, potentially leading to further risk of injury.

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When engaged in a repetitive task our performance fluctuates from trial-to-trial. In particular, inter-trial reaction time variability has been the subject of considerable research. It has been claimed to be a strong biomarker of attention deficits, increases with frontal dysfunction, and predicts age-related cognitive decline. Thus, rather than being just a consequence of noise in the system, it appears to be under the control of a mechanism that breaks down under certain pathological conditions. Although the underlying mechanism is still an open question, consensual hypotheses are emerging regarding the neural correlates of reaction time inter-trial intra-individual variability. Sensory processing, in particular, has been shown to covary with reaction time, yet the spatio-temporal profile of the moment-to-moment variability in sensory processing is still poorly characterized. The goal of this study was to characterize the intra-individual variability in the time course of single-trial visual evoked potentials and its relationship with inter-trial reaction time variability. For this, we chose to take advantage of the high temporal resolution of the electroencephalogram (EEG) acquired while participants were engaged in a 2-choice reaction time task. We studied the link between single trial event-related potentials (ERPs) and reaction time using two different analyses: (1) time point by time point correlation analyses thereby identifying time windows of interest; and (2) correlation analyses between single trial measures of peak latency and amplitude and reaction time. To improve extraction of single trial ERP measures related with activation of the visual cortex, we used an independent component analysis (ICA) procedure. Our ERP analysis revealed a relationship between the N1 visual evoked potential and reaction time. The earliest time point presenting a significant correlation of its respective amplitude with reaction time occurred 175 ms after stimulus onset, just after the onset of the N1 peak. Interestingly, single trial N1 latency correlated significantly with reaction time, while N1 amplitude did not. In conclusion, our findings suggest that inter-trial variability in the timing of extrastriate visual processing contributes to reaction time variability.

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Reaction time (RT), the most common measure of CNS efficiency, shows intra- and inter-individual variability. This may be accounted for by hemispheric specialization, individual neuroanatomy, and transient functional fluctuations between trials. To explore RT on these three levels, ERPs were measured in a visual 4-choice RT task with lateralized stimuli (left lateral, left middle, right middle, and right lateral) in 28 healthy right-handed subjects. We analyzed behavioral data, ERP microstates (MS), N1 and P3 components, and trial-by-trial variance. Across subjects, the N1 component was contralateral to the stimulation side. N1-MSs were stronger over the left hemisphere, and middle stimulation evoked stronger activation than lateral stimulation in both hemispheres. The P3 was larger for the right visual field stimulation. RTs were shorter for the right visual hemifield stimulation/right hand responses. Within subjects, covariance analysis of single trial ERPs with RTs showed consistent lateralized predictors of RT over the motor cortex (MC) in the 112-248 ms interval. Decreased RTs were related to negativity over the MC contralateral to the stimulation side, an effect that could be interpreted as the lateralized readiness potential (LRP), and which was strongest for right side stimulation. The covariance analysis linking individual mean RTs and individual mean ERPs showed a frontal negativity and an occipital positivity correlating with decreased RTs in the 212-232 ms interval. We concluded that a particular RT is a composite measure that depends on the appropriateness of the motor preparation to a particular response and on stimulus lateralization that selectively involves a particular hemisphere.

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Using a modified attention paradigm we investigated specific attentional mechanisms in processing animal feared stimuli. In this paradigm arrays of four pictures were displayed and after its disappearance from view a probe (a letter, X or P) then followed unpredictably in the location of one of the four pictures. The results showed that discriminations of probes tended to be impeded by spider stimuli, compared to snake stimuli. This effect was potentiated by high anxiety but only for those individuals fearful of spiders, since no such effect was observed for snake fearful individuals. Moreover, the discrimination of the probes was not facilitated when presented after the feared stimuli. The implications of these findings are discussed as a function of the cognitive bias involved in specific fear.

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The cortical dynamics of somatosensory processing can be investigated using vibrotactile psychophysics. It has been suggested that different vibrotactile paradigms target different cortical mechanisms, and a number of recent studies have established links between somatosensory cortical function and measurable aspects of behavior. The relationship between cortical mechanisms and sensory function is particularly relevant with respect to developmental disorders in which altered inhibitory processing has been postulated, such as in ASD and ADHD. In this study, a vibrotactile battery consisting of nine tasks (incorporating reaction time, detection threshold, and amplitude- and frequency discrimination) was applied to a cohort of healthy adults and a cohort of typically developing children to assess the feasibility of such a vibrotactile battery in both cohorts, and the performance between children and adults was compared. These results showed that children and adults were both able to perform these tasks with a similar performance, although the children were slightly less sensitive in frequency discrimination. Performance within different task-groups clustered together in adults, providing further evidence that these tasks tap into different cortical mechanisms, which is also discussed. This clustering was not observed in children, which may be potentially indicative of development and a greater variability. In conclusion, in this study, we showed that both children and adults were able to perform an extensive vibrotactile battery, and we showed the feasibility of applying this battery to other (e.g., neurodevelopmental) cohorts to probe different cortical mechanisms.

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In this study, we treated transgenic Huntington's disease (tgHD) model rat with deep brain stimulation (DBS) and evaluated the cognitive and motor outcome. The results showed that the surgery of implanting electrode improved cognition, increased correct rate and decreased response bias in choice reaction time (CRT) task, with similar extent on various genotypes. After long-term DBS to globus pallidus externa( GPe), correct rate was enhanced. The enhancement was genotype related. Additionally, the motor time and reaction time in CRT task reflecting the movement initiation kept the same value, but the chorea-form movement of homozygous rats was rectified prominently after the treatment of DBS. The present results demonstrated that the operation of long-term DBS to globus pallidus externa can improve the cognition and motor outcome of tgHD rats, which implied DBS operation might shed light on HD patients in the future.