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Reaction Time (reaction + time)
Kinds of Reaction Time Terms modified by Reaction Time Selected AbstractsGUSTATORY REACTION TIME AND TIME INTENSITY MEASUREMENTS OF TREHALOSE AND SUCROSE SOLUTIONS AND THEIR MIXTURESJOURNAL OF SENSORY STUDIES, Issue 2 2009MARA VIRGINIA GALMARINI ABSTRACT Dynamic sweetness perception of commercial food grade trehalose, sucrose solutions and their mixtures were studied for a wide range of concentrations. For gustatory reaction time (GRT), concentrations ranged from 2.3 to 13.8% for sucrose and up to 23.0% for trehalose. For time intensity (T-I) sucrose or trehalose solutions (concentration range 2.3,36.8%) and their combinations (23.0 and 36.8% total solids) were analyzed. Trehalose had bigger GRT along the studied range. Both sugars presented similar values for persistence and times of plateau and to maximum intensity, while a significant difference was observed in intensity and GRT at equal concentrations. Trehalose had longer persistence than sucrose in equi -sweet solutions. Overall sweetness profile of some sucrose solutions (i.e., 29.9% sucrose solution and 0.6 sucrose/trehalose ratio mixture at 36.8% total solids) were perceived as similar to mixtures of sucrose/trehalose or single trehalose solutions, which suggests the possibility of sugar replacement without completely modifying sweetness perception. PRACTICAL APPLICATIONS It has been suggested that trehalose may be a potential substitute for sucrose and other sugars used in food formulation because, although its chemical structure is very similar to that of sucrose, it is more stable at low pH and high temperatures. It is not involved in caramelization and does not participate in Maillard reaction with amino acids/proteins. In order to fully establish the potential of trehalose as a functional replacement of sucrose we have determined the sweetness dynamic profile (gustatory reaction time and time-intensity curves) of trehalose solutions and sucrose/trehalose solutions; this aspect is needed for adequately replacing (partially or totally) sucrose in food systems. [source] PREDICTING INJURY FROM FALLS IN OLDER ADULTS: COMPARISON OF VOLUNTARY STEP REACTION TIMES IN INJURED AND NONINJURED FALLERS,A PROSPECTIVE STUDYJOURNAL OF AMERICAN GERIATRICS SOCIETY, Issue 4 2009Itshak Melzer PhD No abstract is available for this article. [source] A COMPUTERIZED SYSTEM FOR CONTROLLING AND MEASURING GUSTATORY REACTION TIMESJOURNAL OF SENSORY STUDIES, Issue 4 2000MIGUELINA GUIRAO ABSTRACT Reaction Time (RT) procedures are widely used in cognitive and behavioral experiments. In the sensory realm RT has been traditionally applied to measure visual, auditory or motor responses. The application of the RT method to gustatory stimuli has proved to be difficult. Attempts to develop automatic control techniques have been restrained by difficulties related to the control of variables, e.g. physiochemical characteristics of chemical solutions and the procedure for stimulus presentation. In this report we describe a computer based system that was designed to measure the reaction time to taste solutions dropped on the tongue. The equipment consists of a pumping system, an interface between the computer and the pumping system, the software required to control the interface and to measure reaction time, and a push button to detect the subject's response. The system can be used as a tool for both research and evaluation tests. [source] Comparing effects of methylphenidate, sertraline and placebo on neuropsychiatric sequelae in patients with traumatic brain injuryHUMAN PSYCHOPHARMACOLOGY: CLINICAL AND EXPERIMENTAL, Issue 2 2005Hoon Lee Abstract Background This study aimed to investigate the effects of methylphenidate and sertraline compared with placebo on various neuropsychiatric sequelae associated with traumatic brain injury (TBI). Methods This was a 4 week, double-blind, parallel-group trial. Thirty patients with mild to moderate degrees of TBI were randomly allocated to one of three treatment groups (n,=,10 in each group) with matching age, gender and education, i.e. methylphenidate (starting at 5,mg/day and increasing to 20,mg/day in a week), sertraline (starting at 25,mg/day and increasing to 100,mg/day in a week) or placebo. At the baseline and at the 4 week endpoint, the following assessments were administered: subjective (Beck Depression Inventory) and objective (Hamilton Depression Rating Scale) measures of depression; Rivermead Postconcussion Symptoms Questionnaire for postconcussional symptoms; SmithKline Beecham Quality of Life Scale for quality of life; seven performance tests (Critical Flicker Fusion, Choice Reaction Time, Continuous Tracking, Mental Arithmetic, Short-Term memory, Digit Symbol Substitution and Mini-Mental State Examination); subjective measures of sleep (Leeds Sleep Evaluation Questionnaire) and daytime sleepiness (Epworth Sleepiness Scale). All adverse events during the study period were recorded and their relationships to the drugs were assessed. Results Neuropsychiatric sequelae seemed to take a natural recovery course in patients with traumatic brain injury. Methylphenidate had significant effects on depressive symptoms compared with the placebo, without hindering the natural recovery process of cognitive function. Although sertraline also had significant effects on depressive symptoms compared with the placebo, it did not improve many tests on cognitive performances. Daytime sleepiness was reduced by methylphenidate, while it was not by sertraline. Conclusions Methylphenidate and sertraline had similar effects on depressive symptoms. However, methylphenidate seemed to be more beneficial in improving cognitive function and maintaining daytime alertness. Methylphenidate also offered a better tolerability than sertraline. Copyright © 2005 John Wiley & Sons, Ltd. [source] Differentiating Type A behaviour and hyperactivity using observed motivation during a reaction time taskINFANT AND CHILD DEVELOPMENT, Issue 2 2003Lilianne Nyberg Abstract In light of the previously found overlap between Type A behaviour as measured by the Matthews Youth Test for Health (MYTH) and hyperactivity scales, the overall aim of this study was to clarify the standing of MYTH-defined Type A behaviour relative to hyperactivity and Attention-Deficit/Hyperactivity Disorder (ADHD), using observed task motivation and performance on a choice reaction-time task, the Complex Reaction Time (CRT) measure. This study included 21 boys exhibiting Type A behaviour, 22 ADHD boys, 20 non-clinically hyperactive boys, and 20 non-hyperactive boys, between the ages of 6 and 13 years. It was proposed that a differentiation of constructs would be possible using observed task motivation if the MYTH were a discriminantly valid measure of Type A behaviour. Results showed that the MYTH-defined Type A group differed from the clinically diagnosed ADHD group, although it was markedly similar to the non-clinical hyperactive group, displaying comparable CRT performance and low level of task motivation. Type A behaviour correlated to CRT performance and task motivation in a way which was conceptually more indicative of hyperactivity than of Type A behaviour, which questions the validity of the MYTH as a measure of the Type A construct. The MYTH Impatience subscale was found to be particularly impure with regard to hyperactivity. Copyright © 2003 John Wiley & Sons, Ltd. [source] Choice Reaction Time and cognitive dysfunction following cardiac surgeryACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 9 2009J. Steinmetz No abstract is available for this article. [source] Implicit memory is independent from IQ and age but not from etiology: evidence from Down and Williams syndromesJOURNAL OF INTELLECTUAL DISABILITY RESEARCH, Issue 12 2007S. Vicari Abstract Background In the last few years, experimental data have been reported on differences in implicit memory processes of genetically distinct groups of individuals with Intellectual Disability (ID). These evidences are relevant for the more general debate on supposed asynchrony of cognitive maturation in children with abnormal brain development. This study, comparing implicit memory processes in individuals with Williams syndrome (WS) and Down syndrome (DS), was planned to verify the ,etiological specificity' hypotheses pertaining to the skill learning abilities of individuals with ID. Method A modified version of Nissen and Bullemer's (1987) Serial Reaction Time (SRT) task was used. The performances of three group were evaluated. The first group consisted of thirty-two people with WS (18 males and 14 females). The second group was comprised of twenty-six individuals with DS (14 males and 12 females). The two groups of individuals with ID were selected so that the groups were comparable as for mental age and chronological age. The third group consisted of forty-nine typically developed children with a mental age similar to that of the groups with WS and DS. Results The two groups of individuals with ID demonstrated different patterns of procedural learning. WS individuals revealed poor implicit learning of the temporal sequence of events characterizing the ordered blocks in the SRT task. Indeed, differently from normal controls, WS participants showed no reaction time (RT) speeding through ordered blocks. Most importantly, the rebound effect, which so dramatically affected normal children's RTs passing from the last ordered to the last block, had only a marginal influence on WS children's RTs. Differently from the WS group, the rate of procedural learning of the participants with DS was comparable to that of their controls. Indeed, DS and typically developed individuals showed parallel RT variations in the series of ordered blocks and, more importantly, passing from the last ordered to the last block. Therefore, a substantial preservation of skill learning abilities in this genetic syndrome is confirmed. Conclusions The results of the present study document that procedural learning in individuals with ID depends on the aetiology of the syndrome, thus supporting the etiological specificity account of their cognitive development. These results are relevant for our knowledge about the qualitative aspects and the underlying neurobiological substrate of the anomalous cognitive development in mentally retarded people. [source] A COMPUTERIZED SYSTEM FOR CONTROLLING AND MEASURING GUSTATORY REACTION TIMESJOURNAL OF SENSORY STUDIES, Issue 4 2000MIGUELINA GUIRAO ABSTRACT Reaction Time (RT) procedures are widely used in cognitive and behavioral experiments. In the sensory realm RT has been traditionally applied to measure visual, auditory or motor responses. The application of the RT method to gustatory stimuli has proved to be difficult. Attempts to develop automatic control techniques have been restrained by difficulties related to the control of variables, e.g. physiochemical characteristics of chemical solutions and the procedure for stimulus presentation. In this report we describe a computer based system that was designed to measure the reaction time to taste solutions dropped on the tongue. The equipment consists of a pumping system, an interface between the computer and the pumping system, the software required to control the interface and to measure reaction time, and a push button to detect the subject's response. The system can be used as a tool for both research and evaluation tests. [source] An in vivo Study of the Relationship between Craving and Reaction Time during Alcohol Detoxification Using the Ecological Momentary AssessmentALCOHOLISM, Issue 12 2005M Lukasiewicz Abstract: Background: To study cognitive interference associated with craving for alcohol, the Ecological Momentary Assessment (EMA) method was used to measure the relationship between craving and reaction time. A secondary aim was the study of the predictive factors for craving during alcohol detoxification. The EMA enables both repeated measures of craving in a natural setting and the recording of reaction time without the patient being aware of this. Methods: Craving for alcohol, reaction time, sadness and anxiety were recorded 8 to 12 times a day, over three weeks of detoxification in 14 alcoholics (n= 1767 measures), on an electronic diary issuing random prompts. Mixed models were used for statistical analysis (,= 5%, 1-,= 88%). Results: Reaction time was significantly increased in univariate analysis when a craving episode occurred but this difference did not persist after multivariate analysis. Craving episodes were more frequent and intense than previously reported. Predictive factors of craving during detoxification were: age, gender, sadness, anxiety and the number of previous detoxifications. Antidepressants, anticraving medications but not benzodiazepines were negatively associated to craving. [source] Variation of Cell Voltage with Reaction Time in Electrochemical Synthesis Process of Sodium DichromateCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 4 2006C. W. Li Abstract To address the problems existing in the traditional production technique of sodium dichromate, a new green technology of producing sodium dichromate with an electrochemical synthesis method was studied. Using a self-made electrosynthesis reactor of pure titanium and stainless steel, with a multiple-unit metal oxides combination anode, a cathode of stainless steel, and a reinforcing combination cation exchange membrane with perfluorosulfonic and perfluorocarboxylic polymers, experiments were carried out on the direct electrochemical synthesis of sodium dichromate from sodium chromate. From the experimental results and electrochemical reaction principles, it was shown that the electrochemical synthesis reaction process of sodium dichromate may be quantitatively determined from the variation of the cell voltage measured macroscopically with reaction time. Cell voltages were experimentally measured at different initial sodium chromate concentrations in the anolyte, and the dependence of the cell voltage on reaction time was discussed. The mathematical model of the variation of cell voltage with reaction time and the change rate equation of cell voltage were established, and satisfactorily formulated the change law of cell voltage in the electrochemical synthesis process of sodium dichromate. [source] The strength of anticipatory spatial biasing predicts target discrimination at attended locations: a high-density EEG studyEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2009Simon P. Kelly Abstract Cueing relevant spatial locations in advance of a visual target results in modulated processing of that target as a consequence of anticipatory attentional deployment, the neural signatures of which remain to be fully elucidated. A set of electrophysiological processes has been established as candidate markers of the invocation and maintenance of attentional bias in humans. These include spatially-selective event-related potential (ERP) components over the lateral parietal (around 200,300 ms post-cue), frontal (300,500 ms) and ventral visual (> 500 ms) cortex, as well as oscillatory amplitude changes in the alpha band (8,14 Hz). Here, we interrogated the roles played by these anticipatory processes in attentional orienting by testing for links with subsequent behavioral performance. We found that both target discriminability (d') and reaction times were significantly predicted on a trial-by-trial basis by lateralization of alpha-band amplitude in the 500 ms preceding the target, with improved speed and accuracy resulting from a greater relative decrease in alpha over the contralateral visual cortex. Reaction time was also predicted by a late posterior contralateral positivity in the broad-band ERP in the same time period, but this did not influence d'. In a further analysis we sought to identify the control signals involved in generating the anticipatory bias, by testing earlier broad-band ERP amplitude for covariation with alpha lateralization. We found that stronger alpha biasing was associated with a greater bilateral frontal positivity at ,390 ms but not with differential amplitude across hemispheres in any time period. Thus, during the establishment of an anticipatory spatial bias, while the expected target location is strongly encoded in lateralized activity in parietal and frontal areas, a distinct non-spatial control process seems to regulate the strength of the bias. [source] An in vivo Study of the Relationship between Craving and Reaction Time during Alcohol Detoxification Using the Ecological Momentary AssessmentALCOHOLISM, Issue 12 2005M Lukasiewicz Abstract: Background: To study cognitive interference associated with craving for alcohol, the Ecological Momentary Assessment (EMA) method was used to measure the relationship between craving and reaction time. A secondary aim was the study of the predictive factors for craving during alcohol detoxification. The EMA enables both repeated measures of craving in a natural setting and the recording of reaction time without the patient being aware of this. Methods: Craving for alcohol, reaction time, sadness and anxiety were recorded 8 to 12 times a day, over three weeks of detoxification in 14 alcoholics (n= 1767 measures), on an electronic diary issuing random prompts. Mixed models were used for statistical analysis (,= 5%, 1-,= 88%). Results: Reaction time was significantly increased in univariate analysis when a craving episode occurred but this difference did not persist after multivariate analysis. Craving episodes were more frequent and intense than previously reported. Predictive factors of craving during detoxification were: age, gender, sadness, anxiety and the number of previous detoxifications. Antidepressants, anticraving medications but not benzodiazepines were negatively associated to craving. [source] Optimisation of kojic acid monolaurate synthesis with lipase PS from Pseudomonas cepaciaJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 6 2002Chee-Shan Chen Abstract To improve the instability of kojic acid in food and cosmetic use, the esterification of kojic acid catalysed by lipase from Pseudomonas cepacia (Amano PS) to synthesise kojic acid monolaurate (KAML) was investigated in this study. Response surface methodology (RSM) with a five-level/five-factor central composite rotatable design (CCRD) was employed to evaluate the effects of synthesis parameters such as reaction time (8,24,h), temperature (35 55,°C), enzyme amount (10,50%), substrate molar ratio of lauric acid to kojic acid (1:1,3:1) and added water content (0,20%) on the percentage molar conversion to KAML by direct esterification. Reaction time and added water content were the most important variables, while substrate molar ratio had less effect on percentage molar conversion. Based on canonical analysis and ridge maximum analysis, optimal synthesis conditions were reaction time 19,h, temperature 44,°C, enzyme amount 38%, substrate molar ratio 2:1 and added water content 10%. The predicted value was 85% and the actual experimental value 82% molar conversion. © 2002 Society of Chemical Industry [source] Dual task interference in psychogenic tremorMOVEMENT DISORDERS, Issue 14 2007Hatice Kumru MD Abstract Psychogenic tremor (PT) is visually indistinguishable from voluntarily mimicked tremor. Healthy volunteers have difficulties with carrying out simultaneously two tasks due to the phenomenon known as dual task interference. Therefore, performing voluntary rhythmic movements would be a burden for carrying out fast ballistic movements with the contralateral hand. We hypothesized that, similarly to healthy volunteers performing rhythmic movements, patients with PT should show the effects of dual task interference, and this may distinguish them from patients with other types of tremor. We studied 6 patients with PT, 9 with Parkinson's disease (PD) and predominantly unilateral tremor, 11 with essential tremor (ET), and 10 normal volunteers (NV) mimicking tremor. They were requested to perform a unilateral simple reaction time task (SRT) to a visual imperative signal in two different conditions: at rest (rSRT) and during contralateral hand tremor (tSRT). Reaction time was significantly longer in tSRT than in rSRT in PT and in NV groups (P < 0.01 for both groups). However, no significant differences were observed between rSRT and tSRT in PD and ET. The delay of unilateral tSRT with respect to rSRT suggests an effect of tremorlike oscillatory movements on reaction time that is consistent with the concept of dual-task interference in NV or PT patients but not in PD or ET. These observations may be useful in the evaluation of psychogenic movement disorders. © 2007 Movement Disorder Society [source] Reaction time is not impaired by stimulation of the ventral-intermediate nucleus of the thalamus (Vim) in patients with tremorMOVEMENT DISORDERS, Issue 3 2002Didier Flament PhD Abstract We studied the effect of high-frequency electrical stimulation of the ventral-intermediate nucleus of the thalamus (Vim) in four patients implanted with chronic stimulators to determine whether this procedure adversely affects reaction time to a proprioceptive stimulus. Two patients had undergone this surgery for treatment of tremor resulting from Parkinson's disease insufficiently responsive to levodopa therapy and two patients for treatment of essential tremor. Reaction times to auditory, visual, cutaneous, and proprioceptive stimuli were tested in a simple motor task requiring flexion of the elbow joint to a visual target in response to each stimulus. Reaction times were tested postoperatively with and without the stimulator turned on. We found that reaction time for all stimulus modalities was not increased when the stimulator was turned on; in fact, reaction times were, on average, slightly shorter during stimulation, but this difference was not statistically significant. We conclude that transmission of somatosensory inputs, necessary for initiating voluntary movement, from the periphery to the cortex is not significantly impaired by stimulation of the ventral-intermediate nucleus of the thalamus in patients with pathological tremor. © 2002 Movement Disorder Society [source] Binocular interaction and performance of visual tasksOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 2 2004Maria S. Justo Abstract Binocular vision implies the fusion of the right and left retinal images to perceive a single image. For this, interocular interaction is required. We measured the reaction times to carry out a visual fixation task in order to determine whether binocular interaction influences performance. Several combinations of test and distraction stimuli were monocularly and binocularly presented to one monkey and three human subjects. The overall median reaction times were 340 ms for the animal and 308, 342 and 381 for human subjects 1, 2 and 3 respectively. Reaction time was shorter when the test stimulus was presented binocularly. Moreover, we observed that the presence of a distraction stimulus increased the reaction time and that a correlated distraction stimulus had a greater influence on this increase than an uncorrelated distraction stimulus. These findings indicate that with binocular vision a more rapid performance of a visual task occurs. [source] Planning of rapid aiming movements and the contingent negative variation: Are movement duration and extent specified independently?PSYCHOPHYSIOLOGY, Issue 3 2009Hartmut Leuthold Abstract In the present study we investigated motor programming constraints implied by the Generalized Motor Program (GMP) view. A response precuing task was used in which participants performed aiming movements of either short or long duration to either a near or a far target position. Precues provided either no advance information or partial information about extent or duration or fully specified the aiming movement. Reaction time (RT) decreased and late Contingent Negative Variation (CNV) amplitude increased with the amount of advance information. In contrast to predictions of the GMP view, the extent precue led to faster responses and larger CNV amplitude than the duration precue. We conclude that late CNV amplitude reflects independent parameter specification processes at an abstract level at which GMP's motor programming constraints do not apply. [source] Reaction time does not predict surgical skillBRITISH JOURNAL OF SURGERY (NOW INCLUDES EUROPEAN JOURNAL OF SURGERY), Issue 10 2003J. Shah Fast is not always best [source] Chemical Recycling and Kinetics of Aqueous Alkaline Depolymerization of Poly(Butylene Terephthalate) WasteCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 7 2004A.S. Goje Abstract Depolymerization reactions of poly(butylene terephthalate) (PBT) waste in aqueous sodium hydroxide solution were carried out in a batch reactor at 80,140,°C at atmospheric pressure by varying PBT particle size in the range of 50,512.5,,m. Reaction time was also varied from 10,110,min to understand the influence of PBT particle size and reaction time on the batch reactor performance. Agitator speed, particle size of PBT and reaction time required were optimized. Disodium terephthalate (salt) and 1,4-butanediol (BD) remain in the liquid phase. BD was recovered by the salting-out method. Disodium terephthalate was separated by acidification to obtain solid terephthalic acid (TPA). The produced monomeric products (TPA and BD) and PBT were analyzed. The yields of TPA and BD were in agreement with PBT conversion. The depolymerization reaction rate was first order to PBT concentration as well as first order to sodium hydroxide concentration. The acid value of TPA changes with the reaction time as well as particle size of PBT. This indicates that PBT molecules get fragmented and hydrolyze simultaneously with aqueous sodium hydroxide to produce BD and disodium terephthalate. Activation energy, Arrhenius constant, equilibrium constant, Gibbs free energy, enthalpy and entropy were determined. The dependence of the hydrolysis rate constant on reaction temperature was correlated by the Arrhenius plot, which shows an activation energy of 25,kJ/mol and an Arrhenius constant of 438,L/min/cm2. [source] Reaction time during semi-automated kinetic perimetry (SKP) in patients with advanced visual field lossACTA OPHTHALMOLOGICA, Issue 1 2010Katarzyna Nowomiejska Abstract. Purpose:, This study aimed to evaluate reaction time (RT) in patients with advanced visual field (VF) loss using semi-automated kinetic perimetry (SKP). Methods:, Seventy-eight patients with advanced VF loss caused by glaucoma (31) or retinitis pigmentosa (19), homonymous VF loss caused by post-chiasmal lesions (18) and unilateral anterior ischaemic optic neuropathy (AION) (10) were examined with SKP (Octopus 101 perimeter). One eye in each patient was enrolled. Additionally, VFs in the 10 healthy fellow eyes of the patients with AION were compared with those in the 10 affected eyes. Reaction time was assessed during the SKP session by presenting kinetic stimuli (III4e) with constant angular velocities of 3 °/second moving linearly along so-called ,RT vectors' at four different locations inside the III4e isoptre. Each stimulus presentation was repeated four times in randomized order. Results:, The geometric mean RT was 794 ms (95% reference interval [RI] 391,1615 ms) in patients with glaucoma, 702 ms (95% RI 306,1608 ms) in patients with retinitis pigmentosa and 675 ms (95% RI 312,1460 ms) in patients with hemianopia. Increases in RT for every 1 ° of eccentricity were 1%, 0.9% and 0.4%, respectively. The geometric mean RT in the 10 patients with unilateral optic neuropathy was 644 ms in affected eyes and 435 ms in unaffected eyes, reflecting an increase of 51% (95% confidence interval 42,62%). Conclusions:, We found substantial inter-subject variability in RT in patients with advanced VF loss. It is possible to correct the position of the isoptres by assessing individual RT. There were no relevant differences in RT between the disease groups. Reaction time increases with eccentricity. In monocular disease (AION), RT is prolonged, compared with in healthy fellow eyes. However, in clinical routine the RT-related displacement of isoptres is negligible in the vast majority of cases. [source] Impaired selection of relevant positive information in depressionDEPRESSION AND ANXIETY, Issue 5 2009Sara M. Levens Ph.D. Abstract Background: A hallmark characteristic of depression is the inability to regulate the effect of emotional material on cognition. Previous research has demonstrated that depressed individuals are less able than are nondepressed persons to expel irrelevant negative information from working memory (WM), thereby exacerbating the effects of negative content on cognition. The primary goal of this study was to examine whether depressed individuals are also impaired at selecting relevant positive content in the context of representations competing for resources in WM; such an impairment would limit depressed persons' ability to use positive material to ameliorate the cognitive effects of negative information. Methods: We administered a Recency-probes task with neutral, positive, and negative words to 20 currently depressed and 22 never-depressed participants. This task assesses the selection of relevant content in WM by inducing interference between current and prior representations of a stimulus in WM. Reaction times to interference and noninterference trials were compared across valence and group to assess how effectively depressed individuals select task-relevant emotional content to resolve interference. Results: Compared to never-depressed controls, depressed individuals were impaired in selecting task-relevant positive stimuli; the performance of the two groups was comparable for selecting task-relevant neutral and negative stimuli. Conclusions: Findings indicate that a valence-specific deficit in WM may contribute to the inability of depressed individuals to regulate emotion, and provide empirical support for formulations that implicate positive insensitivity in the maintenance of depression. Depression and Anxiety, 2009. Published 2009 Wiley-Liss, Inc. [source] Eye remember you two: gaze direction modulates face recognition in a developmental studyDEVELOPMENTAL SCIENCE, Issue 5 2006Alastair D. Smith The effects of gaze direction on memory for faces were studied in children from three different age groups (6,7, 8,9, and 10,11 years old) using a computerized version of a task devised by Hood, Macrae, Cole-Davies and Dias (2003). Participants were presented with a sequence of faces in an encoding phase, and were then required to judge which faces they had previously encountered in a surprise two-alternative forced-choice recognition test. In one condition, stimulus eye gaze was either direct or deviated at the viewing phase, and eyes were closed at the test phase. In another condition, stimulus eyes were closed at the viewing phase, with either direct or deviated gaze at the test phase. Modulation of gaze direction affected hit rates, with participants demonstrating greater accuracy for direct gaze targets compared to deviated gaze targets in both conditions. Reaction times (RT) to correctly recognized stimuli were faster for direct gaze stimuli at the viewing phase, but not at the test phase. The age group of participants differentially affected these measures: there was a greater hit rate advantage for direct gaze stimuli in older children, although RTs were less affected by age. These findings suggest that while the facilitation of face recognition by gaze direction is robust across encoding and recognition stages, the efficiency of the process is affected by the stage at which gaze is modulated. [source] Motor processes in children's imagery: the case of mental rotation of handsDEVELOPMENTAL SCIENCE, Issue 5 2005Marion Funk In a mental rotation task, children 5 and 6 years of age and adults had to decide as quickly as possible if a photograph of a hand showed a left or a right limb. The visually presented hands were left and right hands in palm or in back view, presented in four different angles of rotation. Participants had to give their responses with their own hands either in a regular, palms-down posture or in an inverted, palms-up posture. For both children and adults, variation of the posture of their own hand had a significant effect. Reaction times were longer the more awkward it was to bring their own hand into the position shown in the stimulus photograph. These results, together with other converging evidence, strongly suggest that young children's kinetic imagery is guided by motor processes, even more so than adults'. [source] Sensitivity to visual and auditory stimuli in children with developmental dyslexiaDYSLEXIA, Issue 2 2008Bernardine King Abstract This study considered the extent to which 23 children with dyslexia differed from 23 reading age (RA) and 23 chronological age (CA) matched controls in their ability to make temporal judgements about auditory and visual sequences of stimuli, and in the speed of their reactions to the onsets and offsets of visual and auditory stimuli. The children with dyslexia were slower (p,=,0.039) than the CA controls in their reactions to non-verbal auditory onsets (tones), were less able to recognize the first stimulus of a sequence of tones (p,=,0.022), and were less accurate in identifying the initial phoneme of a sequence of three (p,<,0.001). These characteristics may be manifestations of an impaired temporal processing system for rapid auditory stimuli. CA controls responded more quickly to tone onsets than to tone offsets (p,=,0.025), but the dyslexic and RA groups showed no significant difference (p,>,0.05) in their reaction times to onsets and offsets of these non-verbal auditory stimuli. Dyslexic readers showed impairment compared with CA controls in responding to the last of a sequence of three non-verbal visual stimuli (shapes), p,=,0.02. Reaction times in the visual and auditory onset and offset tasks were richly intercorrelated in the control groups, but the dyslexic group did not show as many significant correlations in reaction times between the auditory and visual domains, or between the onset and offset RTs within each modality. These results suggest that there may be a less integrated cross-modal and intra-modal temporal system in children with dyslexia than in controls. In many of the measures in this study, the performance of the dyslexic group resembled that of the RA control group but differed from CA controls, which implies a developmental delay. The possibility that such a cognitive delay may be related to an underlying neurological disorder is discussed. Copyright © 2007 John Wiley & Sons, Ltd. [source] Involvement of the human frontal eye field and multiple parietal areas in covert visual selection during conjunction searchEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 9 2000Tobias Donner Abstract Searching for a target object in a cluttered visual scene requires active visual attention if the target differs from distractors not by elementary visual features but rather by a feature conjunction. We used functional magnetic resonance imaging (fMRI) in human subjects to investigate the functional neuroanatomy of attentional mechanisms employed during conjunction search. In the experimental condition, subjects searched for a target defined by a conjunction of colour and orientation. In the baseline condition, subjects searched for a uniquely coloured target, regardless of its orientation. Eye movement recordings outside the scanner verified subjects' ability to maintain fixation during search. Reaction times indicated that the experimental condition was attentionally more demanding than the baseline condition. Differential activations between conditions were therefore ascribed to top-down modulation of neural activity. The frontal eye field, the ventral precentral sulcus and the following posterior parietal regions were consistently activated: (i) the postcentral sulcus; (ii) the posterior; and (iii) the anterior part of the intraparietal sulcus; and (iv) the junction of the intraparietal with the transverse occipital sulcus. Parietal regions were spatially distinct and displayed differential amplitudes of signal increase with a maximal amplitude in the posterior intraparietal sulcus. Less consistent activation was found in the lateral fusiform gyrus. These results suggest an involvement of the human frontal eye field in covert visual selection of potential targets during search. These results also provide evidence for a subdivision of posterior parietal cortex in multiple areas participating in covert visual selection, with a major contribution of the posterior intraparietal sulcus. [source] Covariations among fMRI, skin conductance, and behavioral data during processing of concealed informationHUMAN BRAIN MAPPING, Issue 12 2007Matthias Gamer Abstract Imaging techniques have been used to elucidate the neural correlates that underlie deception. The scientifically best understood paradigm for the detection of deception, however, the guilty knowledge test (GKT), was rarely used in imaging studies. By transferring a GKT-paradigm to a functional magnetic resonance imaging (fMRI) study, while additionally quantifying reaction times and skin conductance responses (SCRs), this study aimed at identifying the neural correlates of the behavioral and electrodermal response pattern typically found in GKT examinations. Prior to MR scanning, subjects viewed two specific items (probes) and were instructed to hide their knowledge of these. Two other specific items were designated as targets and required a different behavioral response during the experiment and eight items served as irrelevant stimuli. Reaction times and SCR amplitudes differed significantly between all three item types. The neuroimaging data revealed that right inferior frontal and mid-cingulate regions were more active for probe and target trials compared to irrelevants. Moreover, the differential activation in the right inferior frontal region was modulated by stimulus conflicts. These results were interpreted as an increased top-down influence on the stimulus-response-mapping for concealed and task-relevant items. Additionally, the influence of working memory and retrieval processes on this activation pattern is discussed. Using parametric analyses, reaction times and SCR amplitudes were found to be linearly related to activity in the cerebellum, the right inferior frontal cortex, and the supplementary motor area. This result provides a first link between behavioral measures, sympathetic arousal, and neural activation patterns during a GKT examination. Hum Brain Mapp 2007. © 2007 Wiley-Liss, Inc. [source] Shift of attention in depth in a semi-realistic settingJAPANESE PSYCHOLOGICAL RESEARCH, Issue 3 2002Toshiaki Miura Abstract: This research was based on previous research on the useful field of view in real driving, however shift of attention was examined in depth by the use of an improved tunnel simulator. Despite of the importance of this area of research, nothing like this has been performed previously. The subjects' task was judgment of the relative distance of targets (farther, nearer, or the same), in comparison with a fixation point. Reaction times were measured. There were two variables. One was three observing conditions. Subjects moved at apparent speeds of 40 km/h or 80 km/h or were stationary. The second variable was the validity of the precue concerning the location of the appearance of the target relative to the fixation point. There were three conditions, valid, invalid and or neutral. The results clearly showed that reaction times for nearer targets were shorter than those for farther targets in all conditions. This supports a viewer-centered representation of three-dimensional space. Concerning the direction of shift of attention, reaction time for shift of attention from far locations to near locations was shorter than for the opposite. This difference was more remarkable in the moving condition than in the stationary condition. This was called the rubber band metaphor of attention in locomotion (asymmetrical viewer-centered mode of shift of attention in depth). These results are ecologically valid. Possible underlying mechanisms are discussed from the viewpoint of distribution of attention resource. [source] Multitasking: Association Between Poorer Performance and a History of Recurrent FallsJOURNAL OF AMERICAN GERIATRICS SOCIETY, Issue 4 2007Kimberly A. Faulkner PhD OBJECTIVES: To examine the association between poorer performance on concurrent walking and reaction time and recurrent falls. DESIGN: Cross-sectional analysis. SETTING: Community. PARTICIPANTS: Three hundred seventy-seven older community-dwelling adults (mean age±standard deviation 78±3). MEASUREMENTS: Reaction times on push-button and visual-spatial decision tasks were assessed while seated and while walking a 20-m course (straight walk) and a 20-m course with a turn at 10 m (turn walk). Walking times were recorded while walking only and while performing a reaction-time response. Dual-task performance was calculated as the percentage change in task times when done in dual-task versus single-task conditions. A history of recurrent falls (,2 vs ,1 falls) in the prior 12 months was self-reported. Multivariate logistic regression models were used to predict the standardized odds ratios (ORs) of recurrent falls history. The standardized unit for dual-task performance ORs was interquartile range/2. RESULTS: On the push-button task during the turn walk, poorer reaction time response (slower) was associated with 28% lower (P=.04) odds of recurrent fall history. On the visual-spatial task, poorer walking-time response (slower) was associated with 34% (P=.02) and 42% (P=.01) higher odds of recurrent falls history on the straight and turn walks, respectively. CONCLUSION: These findings suggest that walking more slowly in response to a visual-spatial decision task may identify individuals at risk for multiple falls. Prospective studies are needed to confirm the prognostic value of poor walking responses in a dual-task setting for multiple falls. [source] Reaction time is not impaired by stimulation of the ventral-intermediate nucleus of the thalamus (Vim) in patients with tremorMOVEMENT DISORDERS, Issue 3 2002Didier Flament PhD Abstract We studied the effect of high-frequency electrical stimulation of the ventral-intermediate nucleus of the thalamus (Vim) in four patients implanted with chronic stimulators to determine whether this procedure adversely affects reaction time to a proprioceptive stimulus. Two patients had undergone this surgery for treatment of tremor resulting from Parkinson's disease insufficiently responsive to levodopa therapy and two patients for treatment of essential tremor. Reaction times to auditory, visual, cutaneous, and proprioceptive stimuli were tested in a simple motor task requiring flexion of the elbow joint to a visual target in response to each stimulus. Reaction times were tested postoperatively with and without the stimulator turned on. We found that reaction time for all stimulus modalities was not increased when the stimulator was turned on; in fact, reaction times were, on average, slightly shorter during stimulation, but this difference was not statistically significant. We conclude that transmission of somatosensory inputs, necessary for initiating voluntary movement, from the periphery to the cortex is not significantly impaired by stimulation of the ventral-intermediate nucleus of the thalamus in patients with pathological tremor. © 2002 Movement Disorder Society [source] S-cone excitation ratios for reaction times to blue-yellow suprathreshold changes at isoluminanceOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 5 2010José M. Medina Abstract We examined different contrast metrics to scale visual latencies for suprathreshold stimuli modulated along tritan confusion lines. S-cone increments (,blue') and decrements (,yellow') were isolated along two different tritan confusion lines, each one having a different luminance value. Reaction times (RT) were evaluated as a function of the Weber contrast and the S-cone excitation ratio between the test stimulus and the background. RTs were described using a model that generalizes Piéron's law and incorporates the notion of threshold units and power law scaling. Our results show that RTs for S-cone increments and decrements equate better when using the S-cone excitation ratio. However, a single function did not describe all RT data. S-cone RTs are better described by separate functions. We conclude that S-cone increments and decrements do not scale in the same manner. Both Weber contrast and the S-cone excitation ratio are plausible metrics at isoluminance. The implications for the S-cone pathways are discussed. [source] | |||||||||||||||||||||||||||||||||||||||||||