Lengthening Of Reaction Time Research Articles

Dopamine Increases Accuracy and Lengthens Deliberation Time in Explicit Motor Skill Learning.

Although animal research implicates a central role for dopamine in motor skill learning, a direct causal link has yet to be established in neurotypical humans. Here, we tested if a pharmacological manipulation of dopamine alters motor learning, using a paradigm which engaged explicit, goal-directed strategies. Participants (27 females; 11 males; aged 18-29 years) first consumed either 100 mg of levodopa (n = 19), a dopamine precursor that increases dopamine availability, or placebo (n = 19). Then, during training, participants learnt the explicit strategy of aiming away from presented targets by instructed angles of varying sizes. Targets jumped mid-movement by the instructed aiming angle. Task success was thus contingent upon aiming accuracy and not speed. The effect of the dopamine manipulations on skill learning was assessed during training and after an overnight follow-up. Increasing dopamine availability at training improved aiming accuracy and lengthened reaction times, particularly for larger, more difficult aiming angles, both at training and, importantly, at follow-up, despite prominent session-by-session performance improvements in both accuracy and speed. Exogenous dopamine thus seems to result in a learnt, persistent propensity to better adhere to task goals. Results support the proposal that dopamine is important in engagement of instrumental motivation to optimize adherence to task goals, particularly when learning to execute goal-directed strategies in motor skill learning.

Effects of three-dimension movie visual fatigue on cognitive performance and brain activity.

To further develop three-dimensional (3D) applications, it is important to elucidate the negative effects of 3D applications on the human body and mind. Thus, this study investigated differences in the effects of visual fatigue on cognition and brain activity using visual and auditory tasks induced by watching a 1-h movie in two dimensions (2D) and 3D. Eighteen young men participated in this study. Two conditions were randomly performed for each participant on different days, namely, watching the 1-h movie on television in 2D (control condition) and 3D (3D condition). Before and after watching the 1-h movie on television, critical flicker fusion frequency (CFF: an index of visual fatigue), and response accuracy and reaction time for the cognitive tasks were determined. Brain activity during the cognitive tasks was evaluated using a multi-channel near-infrared spectroscopy system. In contrast to the control condition, the decreased CFF, and the lengthened reaction time and the decreased activity around the right primary somatosensory cortex during Go/NoGo blocks in the visual task at post-viewing in the 3D condition were significant, with significant repeated measures correlations among them. Meanwhile, in the auditory task, the changes in cognitive performance and brain activity during the Go/NoGo blocks were not significant in the 3D condition. These results suggest that the failure or delay in the transmission of visual information to the primary somatosensory cortex due to visual fatigue induced by watching a 3D movie reduced the brain activity around the primary somatosensory cortex, resulting in poor cognitive performance for the visual task. This suggests that performing tasks that require visual information, such as running in the dark or driving a car, immediately after using a 3D application, may create unexpected risks in our lives. Thus, the findings of this study will help outlining precautions for the use of 3D applications.

Manual and Spoken Cues in French Sign Language's Lexical Access: Evidence From Mouthing in a Sign-Picture Priming Paradigm.

Although Sign Languages are gestural languages, the fact remains that some linguistic information can also be conveyed by spoken components as mouthing. Mouthing usually tend to reproduce the more relevant phonetic part of the equivalent spoken word matching with the manual sign. Therefore, one crucial issue in sign language is to understand whether mouthing is part of the signs themselves or not, and to which extent it contributes to the construction of signs meaning. Another question is to know whether mouthing patterns constitute a phonological or a semantic cue in the lexical sign entry. This study aimed to investigate the role of mouthing on the processing of lexical signs in French Sign Language (LSF), according the type of bilingualism (intramodal vs. bimodal). For this purpose, a behavioral sign-picture lexical decision experiment was designed. Intramodal signers (native deaf adults) and Bimodal signers (fluent hearing adults) have to decide as fast as possible whether a picture matched with the sign seen just before. Five experimental conditions in which the pair sign-mouthing were congruent or incongruent were created. Our results showed a strong interference effect when the sign-mouthing matching was incongruent, reflected by higher error rates and lengthened reaction times compared with the congruent condition. This finding suggests that both groups of signers use the available lexical information contained in mouthing during accessing the sign meaning. In addition, deaf intramodal signers were strongly interfered than hearing bimodal signers. Taken together, our data indicate that mouthing is a determining factor in LSF lexical access, specifically in deaf signers.

Older adults rely on somatosensory information from the effector limb in the planning of discrete movements to somatosensory cues

While younger and older adults can perform upper-limb reaches to spatial targets with comparable endpoint accuracy (i.e., Helsen et al., 2016; Goodman et al., 2020), movement planning (i.e., reaction time) is significantly longer in older versus younger adults (e.g., Pohl et al., 1996; Goodman et al., 2020). Critically relevant to the current study, age-related differences in reaction time are even greater when older adults plan movement towards somatosensory versus visual or bimodal targets in the absence of vision of the moving limb (e.g., Goodman et al., 2020). One proposed explanation of these lengthened reaction times to somatosensory targets is that older adults may be experiencing challenges in implementing sensorimotor transformations when planning discrete movements of their unseen limb. To test this idea and assess the contributions of somatosensory information to these motor planning processes, tendon vibration was applied to the muscles of the effector limb between reaching movements made towards visual, somatosensory, or bimodal targets. The results revealed that older adults show the greatest increases in reaction times when vibration was applied during the preparation of movements to somatosensory targets. Further, both older and younger adults exhibited decreased movement endpoint precision when tendon vibration was applied. However, only older adults showed significantly lower movement endpoint precision due to tendon vibration when making movements to somatosensory targets, versus both visual and bimodal targets. These results corroborate previous evidence that older adults have difficulties planning upper-limb movements to somatosensory targets. As well, these results yielded novel evidence that such motor planning processes in older adult rely on somatosensory cues from the effector limb.

Alterations Functional Connectivity in Temporal Lobe Epilepsy and Their Relationships With Cognitive Function: A Longitudinal Resting-State fMRI Study.

Background: Cognitive impairments in temporal lobe epilepsy (TLE) patients has been described as a chronically progressive feature of the disease. However, how severe recurrent seizures modify neuronal circuits in the human brain and subsequently degrade cognitive function, remains largely unknown. Here, we aimed to investigate longitudinal alterations by functional magnetic resonance imaging (fMRI) in TLE patients and to assess how those alterations are related to cognitive function performance.Methods: Sixteen TLE patients and 20 normal controls (NCs) were recruited for a study to observe longitudinal alterations in resting-state functional connectivity (FC) and to estimate alertness, orientation, and executive function both at baseline and at a follow-up time ~3 years later.Results: TLE patients, compared with NCs, showed impaired executive function, intrinsic alertness, and phasic alertness and exhibited lengthened reaction time (RT) in the spatial cue and center cue conditions at baseline. The orienting function of TLE patients was declined at follow-up compared to the baseline. Cross-sectional analysis demonstrated that TLE patients displayed significantly greater positive correlation than NCs between the right dorsolateral prefrontal cortex (DLPFC) and the right inferior parietal lobule (IPL) and right superior frontal gyrus (SFG). Furthermore, among TLE patients, the longitudinal study revealed a decrease in correlation between the right DLPFC and the right SFG compared to the baseline. In addition, there was a significant negative correlation between the longitudinal change in FC and the change in orienting function in TLE subjects.Conclusions: Abnormal connectivity between the DLPFC and the SFG suggests the potential of longitudinal resting-state fMRI to delineate regions relevant to cognitive dysfunction for disease progression.

Hydrodeoxygenation of lignin-derived phenolic compounds into aromatic hydrocarbons under low hydrogen pressure using molybdenum oxide as catalyst

MoO3 catalyst was prepared by calcination using (NH4)6Mo7O24·4H2O as precursor and was characterized by XRD, XPS, H2-TPR and low temperature N2 adsorption. Hydrodeoxygenation of phenol was conducted to investigate the catalytic performance of MoO3 catalyst at lower H2 pressure. Effects of reaction temperature, reaction time and N2 partial pressure on the phenol conversion and product distribution were tested carefully. MoO3 catalyst was found to preferentially produce arenes with high selectivity, while at lengthened reaction time cyclohexane selectivity was increased gradually. Oxygen vacancy site of MoO3 (Mo5+) was deemed to be the active center in the hydrodeoxygenation of phenol, which accounts for the cleavage of CAR-OH to benzene. In addition, MoO3 catalyzed HDO reactions were further tested using different phenolic compounds as reactants. Experimental results suggest MoO3 catalyst can be widely applied in the conversion of diverse lignin-derived phenolic compounds conversion to aromatic hydrocarbons.

Prefrontal dysfunction in remitted depression at work reinstatement using near-infrared spectroscopy

A long-term and/or recurrent sickness absence from work due to depression has been an important health problem in industrial countries. In addition, previous sick leave is a risk factor of recurrence. However, many characteristics, especially biological aspects, have not been investigated in remitted depressive patients who were ready to return to work from sickness absence. Therefore, the purpose of this study is to clarify the pathophysiological characteristics of patients who were at risk for recurrence of sickness absence. We recruited 21 patients and 16 healthy control subjects. All patients were ready to return to work within one month from long-term sickness absence. All subjects were examined for prefrontal function represented by oxyHb changes during the verbal fluency task (VFT) and the Stroop task using near-infrared spectroscopy. Suppressed prefrontal reaction during the VFT and increased prefrontal reaction during the Stroop task were observed in the patient group compared with the control group. Significantly lengthened reaction time was observed in the incongruent condition in the patient group during the Stroop task. Depressive patients showed impaired executive function measured by the Stroop task and had prefrontal dysfunction despite clinical remission. Residual prefrontal dysfunction may be one biological reason for repetitive sickness absence.

Marijuana and Chronic Nonmalignant Pain in Adolescents

C hronic nonmalignant pain in children and adolescents occurs worldwide and can be associated with a lower selfreported quality of life. Headache, abdominal pain, or musculoskeletal pain is the most common complaint. Comorbid symptoms such as fatigue, sleep disturbance, depression, and anxietymay exacerbate pain andcontribute tonotable disability, psychological distress, and impaired functioning. Patients may find it difficult to attend school, concentrate on homework, socialize with friends, or engage in physical activityd ie, activities at the core of being a normal adolescent (patients 13-17 years of age)ddue to ongoing pain. In affected adolescents, evaluations and medical tests may be undertaken over months or longer, with protracted investigations often failing to determine the etiology. Many patients have had unsuccessful medication trials and procedures engendering frustration that “something is being missed.” Patients expect a “quick fix” that, when not forthcoming, may cause them to turn to alternative treatments. Marijuana is one such treatment. Given its widespread availability throughout the United States and expanded use for medical conditions, it is reasonable to anticipate increasing numbers of adolescents turning to marijuana to treat chronic pain. There is a paucity of original research data regarding risks and benefits of marijuana use for treating chronic pain in adults, and there is even less data for treating adolescents. Although benefits may accrue in specific conditions, adverse effects influencing daily functioning (eg, impaired concentration or lengthened reaction time when performing tasks) often limit treatment. More studies are needed in all ages of patients to determine if marijuana effectively reduces chronic nonmalignant pain, withoutmajor adverse effects worsening debility. We could find only one study describing marijuana use to manage pain, mood, and sleep disturbances in an adolescent population. A limitation of this study was its failure to describe participants’ ability to function daily while using marijuana. In this commentary, we describe how marijuana use in 3 adolescent patients presenting to a pediatric chronic pain clinic may have contributed to their functional difficulties. We offer speculative synthesis about the consequences of marijuana consumption and appropriate methods for patient management. During their evaluations, the described patients volunteered that they used marijuana regularly. Urine drug screens are not routinely performed in our clinic and were not used to evaluate these 3 patients. Institutional review board approval was obtained before reporting.

Electrodermal responses to sources of dual-task interference

There is a response selection bottleneck that is responsible for dual-task interference. How the response selection bottleneck operates was addressed in three dual-task experiments. The overlap between two tasks (as indexed by the stimulus onset asynchrony [SOA]) was systematically manipulated, and both reaction time and electrodermal activity were measured. In addition, each experiment also manipulated some aspect of the difficulty of either task. Both increasing task overlap by reducing SOA and increasing the difficulty of either task lengthened reaction times. Electrodermal response was strongly affected by task difficulty but was only weakly affected by SOA, and in a different manner from reaction time. A fourth experiment found that the subjectively perceived difficulty of a dual-task trial was affected both by task difficulty and by SOA, but in different ways than electrodermal activity. Overall, the results were not consistent with a response selection bottleneck that involves processes of voluntary, executive attention. Instead, the results converge with findings from neural network modeling to suggest that the delay of one task while another is being processed reflects the operation of a routing mechanism that can process only one stream of information for action at a time and of a passive, structural store that temporarily holds information for the delayed task. The results suggest that conventional blocked or event-related neuroimaging designs may be inadequate to identify the mechanism of operation of the response selection bottleneck.

Attentional capture by motion onsets is modulated by perceptual load

The onset of motion captures attention during visual search even if the motion is not task relevant, which suggests that motion onsets capture attention in a stimulus-driven manner. However, we have recently shown that stimulus-driven attentional capture by abruptly appearing objects is attenuated under conditions of high perceptual load. In the present study, we examined the influence of perceptual load on attentional capture by another type of dynamic stimulus: the onset of motion. Participants searched for a target letter through briefly presented low- and high-load displays. On each trial, two irrelevant flankers also appeared, one with a motion onset and one that was static. Flankers defined by a motion onset captured attention in the low-load but not in the high-load displays. This modulation of capture in high-load displays was not the result of overall lengthening of reaction times (RTs) in this condition, since search for a single low-contrast target lengthened RTs but did not influence capture. These results, together with those of previous studies, suggest that perceptual load can modulate attentional capture by dynamic stimuli.

Attentional capture by motion onsets is modulated by perceptual load

The onset of motion captures attention during visual search even if the motion is not task relevant, which suggests that motion onsets capture attention in a stimulus-driven manner. However, we have recently shown that stimulus-driven attentional capture by abruptly appearing objects is attenuated under conditions of high perceptual load. In the present study, we examined the influence of perceptual load on attentional capture by another type of dynamic stimulus: the onset of motion. Participants searched for a target letter through briefly presented low- and high-load displays. On each trial, two irrelevant flankers also appeared, one with a motion onset and one that was static. Flankers defined by a motion onset captured attention in the low-load but not in the high-load displays. This modulation of capture in high-load displays was not the result of overall lengthening of reaction times (RTs) in this condition, since search for a single low-contrast target lengthened RTs but did not influence capture. These results, together with those of previous studies, suggest that perceptual load can modulate attentional capture by dynamic stimuli.

Slow Motor Responses to Visual Stimuli of Low Salience in Autism

ABSTRACT The authors studied 2 tasks that placed differing demands on detecting relevant visual information and generating appropriate gaze shifts in adults and children with and without autism. In Experiment 1, participants fixated a cross and needed to make large gaze shifts, but researchers provided explicit instructions about shifting. Children with autism were indistinguishable from comparison groups in this top-down task. In Experiment 2 (bottom-up), a fixation cross remained or was removed prior to the presentation of a peripheral target of low visual salience. In this gap–effect experiment, children with autism showed lengthened reaction times overall but no specific deficit in overlap trials. The results show evidence of a general deficit in manual responses to visual stimuli of low salience and no evidence of a deficit in top-down attention shifting. Older children with autism appeared able to generate appropriate motor responses, but stimulus-driven visual attention seemed impaired.

Blood lead levels and specific attention effects in young children

The detrimental effects of early exposure to lead are credible and persistent, but there is presently no agreement on a safe threshold for circulating lead levels. Although several research groups have found significantly poorer cognitive performance in children who have whole blood levels as low as 5 μg/dL, most government agencies, including the EPA and the CDC, continue to use 10 μg/dL as the criterion for concern in public health advisories. Prior research has consistently indicated a negative relation between lead levels and attention. Similarly, the results of the present study show a relation between blood lead level and neurobehavioral outcome in 7-year-old children ( N = 506). Higher lead levels were associated significantly with decreased scores on measures of intelligence (i.e., overall, performance and verbal IQ), lengthened reaction time, hyperactivity, and social and delinquent behavior problems. Importantly, the present study documents a significant negative impact of blood lead levels on attention, but not impulsivity, in early elementary age children, further delineating the specific aspects of attention related to blood lead concentrations. Analyses were also conducted to identify a “safe” blood lead level threshold. Visual inspection of non-parametric regression plots suggested a gradual linear dose–response relationship for each endpoint. None of the neurobehavioral outcomes assessed showed evidence of a threshold under which lead levels appear to “safe”. In light of the consistency of these findings with those of several other groups, it is advisable to consider whether the threshold for an acceptable blood lead level should be reduced.

TMS can reveal contrasting functions of the dorsal and ventral visual processing streams

In order to investigate the functional specificity of the dorsal and ventral visual processing steams we used transcranial magnetic stimulation (TMS) to briefly disrupt one or the other while subjects performed three tasks, involving discrimination of colour or shape or relative position. TMS was delivered over right posterior parietal cortex (PPC) or right lateral occipital (LO) cortex, regions known to have visuo-spatial and object processing properties respectively. LO but not PPC stimulation had a significant effect on reaction time when subjects were asked to make a discrimination of relative shape. PPC stimulation had a significant effect when subjects were asked to discriminate relative position of the same shapes. Stimulation of LO also lengthened reaction times on the position task. There were no effects of stimulation at either site on colour discrimination. Results are discussed within the framework of how the dorsal stream and ventral stream are dissociated following their damage in neurological patients and possible ways in which they may interact in the normal brain.

Cognition in the early stage of multiple sclerosis

Cognitive dysfunctions may contribute to limitation of everyday activities of patients with multiple sclerosis (MS). Recent studies have demonstrated that 45 to 65% of MS-patients are cognitively impaired. The profile of MS-related cognitive dysfunctions varies greatly. It includes memory and learning deficits, attention deficits, executive dysfunctions and visuo-spatial deficits. Most studies of cognition in MS examined patients in later stages, often including MS-patients with marked physical disabilities. Studies of cognitive dysfunctions in the early stage of the disease are rare. This study specifically aimed at evaluating and characterizing cognitive impairments in the early stage of MS, and determining specific patterns of cognitive dysfunction. 21 MS patients, experiencing their first neurological symptoms not more than two years previously, and 22 healthy controls were compared. A comprehensive neuropsychological test-battery was used to evaluate MS-related cognition. The battery consisted of memory and learning tests, executive functioning tests and a visuo spatial functioning test. A computerized attention test-battery was also included, which assess accuracy and speed of test responses. In addition depression and intellectual capabilities were assessed. Compared with healthy controls, MS-patients in the early stage of the disease performed significantly lower on each neuropsychological assessment, except for verbal short-term memory. In particular, MS-patients showed a lengthened reaction time for simple and focused attention (19-38%), impaired non-verbal memory function (RVDLT recognition: 33%) and a planning deficit (24%). Associations between information processing speed and disease course and the employment situation were additionally found. However, patients did not have clinically relevant depression rates on the ADS-L and visuo spatial abilities remain preserved. Our findings revealed discrete cognitive dysfunction in MS-patients within the early stage of the disease.

Prefrontal and parietal cortex in human episodic memory: an interference study by repetitive transcranial magnetic stimulation

Neuroimaging findings, including repetitive transcranial magnetic stimulation (rTMS) interference, point to an engagement of prefrontal cortex (PFC) in learning and memory. Whether parietal cortex (PC) activity is causally linked to successful episodic encoding and retrieval is still uncertain. We compared the effects of event-related active or sham rTMS (a rapid-rate train coincident to the very first phases of memoranda presentation) to the left or right intraparietal sulcus, during a standardized episodic memory task of visual scenes, with those obtained in a fully matched sample of subjects who received rTMS on left or right dorsolateral PFC during the same task. In these subjects, specific hemispheric effects of rTMS included interference with encoding after left stimulation and disruption of retrieval after right stimulation. The interference of PC-rTMS on encoding/retrieval performance was negligible, lacking specificity even when higher intensities of stimulation were applied. However, right PC-rTMS of the same intensity lengthened reaction times in the context of a purely attentive visuospatial task. These results suggest that the activity of intraparietal sulci shown in several functional magnetic resonance studies on memory, unlike that of the dorsolateral PFC, is not causally engaged to a useful degree in memory encoding and retrieval of visual scenes. The parietal activations accompanying the memorization processes could reflect the engagement of a widespread brain attentional network, in which interference on a single 'node' is insufficient for an overt disruption of memory performance.

Polymerization reaction in restricted space of layered double hydroxides (LDHs)

This paper reported the preparation of styrene sulfonate intercalated layered double hydroxides (LDHs) material, SS-LDHs by coprecipitation method, followed byin-situ polymerization of the monomers in the interlayer space of LDHs. The polymerization reaction was monitored by UV and NMR. It is confirmed that when the reaction occurred at 100°C for 24 h, part of monomers did not react. When the reaction was carried out at 150°C., the polymerization of the intercalated monomers is complete to afford the polymer intercalated product PSS-LDHs. During the polymerization process, the layered structure remains well. At the same time the gallery height increases with the lengthening of reaction time. This is preliminarily because that the PSS becomes more swelling with the amount of water it absorbs due to its hygroscopicity property.

Influence of Sleep Deprivation and Auditory Intensity on Reaction Time and Response Force

Arousal and activation are two variables supposed to underlie change in response force. This study was undertaken to explain these roles, specifically, for strong auditory stimuli and sleep deficit. Loud auditory stimuli can evoke phasic overarousal whereas sleep deficit leads to general underarousal. Moreover, Van der Molen and Keuss (1979, 1981) showed that paradoxically long reaction times occurred with extremely strong auditory stimuli when the task was difficult, e.g., choice reaction or Simon paradigm. It was argued that this paradoxical behavior related to reaction time is due to active disconnecting of the coupling between arousal and activation to prevent false responses. If so, we predicted that for extremely loud stimuli and for difficult tasks, the lengthening of reaction time should be associated with reduction of response force. The effects of loudness and sleep deficit on response time and force were investigated in three different tasks: simple response, choice response, and Simon paradigm. According to our expectation, we found a detrimental effect of sleep deficit on reaction time and on response force. In contrast to Van der Molen and Keuss, we found no increase in reaction time for loud stimuli (up to 110 dB) even on the Simon task.

In briefs

A recent Transport Research Laboratory study (commissioned by Direct Line Insurance) into the use of mobile phones while driving, produced stark results. When talking on a hand-held mobile phone in a driving simulator, drivers’ reaction times were, on average, 50% slower than normal, and 30% slower than when driving at the UK legal alcohol limit. In reacting to a stop signal when driving at 70 mph, these lengthened reaction times meant drivers talking on a hand-held mobile travelled an average 46 ft further than normal before coming to a halt. Those talking on a ‘hands-free’ kit, or driving ‘drunk’ travelled 26 ft and 12 ft further, respectively. Unsurprisingly perhaps, sending text-messages was the most distracting activity of all. These findings should add further weight to calls for a specific law banning the use of mobile phones whilst driving. CBJ

INFLUENCE OF SLEEP DEPRIVATION AND AUDITORY INTENSITY ON REACTION TIME AND RESPONSE FORCE

Arousal and activation are two variables supposed to underlie change in response force. This study was undertaken to explain these roles, specifically, for strong auditory stimuli and sleep deficit. Loud auditory stimuli can evoke phasic over-arousal whereas sleep deficit leads to general underarousal. Moreover, Van der Molen and Keuss. (1979, 1981) showed that paradoxically long reaction times occurred with extremely strong auditory stimuli when the task was difficult, e.g., choice reaction or Simon paradigm. It was argued that this paradoxical behavior related to reaction time is due to active disconnecting of the coupling between arousal and activation to prevent false responses. If so, we predicted that for extremely loud stimuli and for difficult tasks, the lengthening of reaction time should be associated with reduction of response force. The effects of loudness and sleep deficit on response time and force were investigated in three different tasks: simple response, choice response, and Simon paradigm. According to our expectation, we found a detrimental effect of sleep deficit on reaction time and on response force. In contrast to Van der Molen and Keuss, we found no increase in reaction time for loud stimuli (up to 110 dB) even on the Simon task.