Redundancy-associated deficit in schizophrenic reaction time performance.

Examined the influence of information redundancy on the reaction-time performance of 3 groups of females: 36 hospitalized schizophrenics defined as process or reactive by the Elgin Prognostic Rating Scale; 18 nonschizophrenic psychiatric-patient controls; and 18 normal hospital staff controls. The influence of information redundancy was assessed by manipulating the degree of regularity in the presentation of preparatory interval (PI) durations. Runs of 2 and 4 identical PIs, defined as low and high redundant sets, respectively, were embedded in an irregular order of trials to test the influence associated with regular presentation. In contrast to previous analyses showing that the irregular vs. regular presentation condition interacts with PI duration, the interaction was found for process patients only. This interaction took the form of a "crossover" in which the regular PI trials yielded worse performance than the irregular trials at long PI durations; the opposite was true for short durations. Redundant PIs tended to show an improved performance immediately and then, for the process group only, a progressive loss on successive trials. An interpretation in light of D. Shakow's (see record 1965-08514-001) "set theory" and an inhibitory process explanation are disucssed. (25 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Time-linked impairment in schizophrenic reaction time performance.

Reports on the disruptive influence of uncertain visual probe stimuli on schizophrenic reaction time performance as a function of both the time since the onset of the probe stimuli and the pathology level of the Ss. Two studies were conducted, using 32 process schizophrenics, 16 reactive schizophrenics, 16 nonschizophrenic patients (alcoholic, immature personality, and depression diagnoses), and 16 normal controls. Mean ages of Ss ranged from 28.2 to 37.1 yrs. Probe trials were imbedded within standard series of regular reaction time trials. Both process and reactive schizophrenics were impaired by this stimulation on trials with only a 1-sec preparatory interval. Process schizophrenics showed impairment at the longest (9-sec) trials following recovery at midrange durations. The midrange recovery and long trial impairment of the process schizophrenics was a pattern strongly related to degree of pathology. The same U-shaped pattern—early and late impairment with intermediate recovery—and a similar relationship of the reaction time pattern to pathology level were found again in a 2nd sample of process schizophrenics who were given less intense visual stimulation on the probe trials. The U-shaped patterns obtained for the process schizophrenics in both studies are thought to reflect inadequate modulation of inhibitory controls. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contextual influences on crossover in the reaction time performance of schizophrenics.

Conducted 3 investigations with a total of 55 female process schizophrenics and 54 normal controls to test the resilience of the crossover phenomenon observed in schizophrenic reaction time performance. The crossover effect portrays an interaction of the predictability (regularity) and the duration of the delay (preparatory interval) factors in the simple reaction time procedure. The effect, believed pathognomonic of schizophrenic reaction time performance, shows performance on regular trials to be faster than irregularly presented trials at short duration, but the regular presentation of trials is slower at longer duration preparatory intervals. The present studies tested an interpretation that the difference between the regular and irregular trials with long preparatory intervals might be dependent on the influence of certain contextual influences operating within the arrangement of trials. Findings show that the contextual factors studied did not account for this difference. Neither eliminating the presence of shorter trials preceding the irregular test trials nor loading the series with short duration trials substantially influenced the extent to which the long regular trials were slower than the long irregular trials. As observed before, the crossover characterized the process schizophrenic group and was not characteristic of the reactive schizophrenic or normal control groups. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On the relation of mean reaction time and intraindividual reaction time variability.

Researchers often statistically control for means when examining individual or age-associated differences in variances, assuming that the relation between the 2 is linear and invariant within and across individuals and age groups. We tested this assumption in the domain of working memory by applying variance-heterogeneity multilevel models to reaction times in the n-back task. Data are from the COGITO study, which comprises 101 younger and 103 older adults assessed in over 100 daily sessions. We found that relations between means and variances vary reliably across age groups and individuals, thereby contradicting the invariant linearity assumption. We argue that statistical control approaches need to be replaced by theoretical models that simultaneously estimate central tendency and dispersion of latencies and accuracies and illustrate this claim by applying the diffusion model to the same data. Finally, we note that differences in reliability between estimates for means and variances need to be considered when comparing their unique contributions to developmental outcomes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Relation between latency and redundancy-associated deficit in schizophrenic reaction time performance.

Evaluated the independence of 2 well-established measures of information-processing difficulties in process schizophrenics, namely, reaction time measures of latency and redundancy-associated deficit. Training exercises were designed to improve the speed of reaction time performance in 16 male Ss (average age 32.5 yrs). These exercises were successful in reducing latency over the course of training and from pre- to posttraining assessments to levels falling around the range of performance expected of normals. Redundancy-associated deficit, however, did not change from pre- to postassessment, indicating that this index is not a simple reflection of latency and is not responsive to training procedures involving positive motivation. Intercorrelations of the 2 indexes also showed that these measures were independent, at least within the process end of the schizophrenic spectrum. Furthermore, the 2 measures correlated with different types of S factors. Latency measures correlated with measures of chronicity, and the redundancy-deficit measure was correlated with prognosis. Findings help to clarify the utility of reaction time indexes as markers of various aspects of schizophrenic pathology. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effect of divided attention on probe reaction time in multiple-task performance.

Examined information processing demands in 5 experiments in which a total of 72 candidates who were being processed for aircrew selection and pilot training performed a serial addition, pursuit tracking, or probe reaction time (PRT) task separately and in dual- and triple-task combinations. The experiments manipulated the assigned priority and the capacity requirements of the serial addition and tracking tasks. PRT is usually assumed to reflect spare processing capacity in dual-task studies and to increase with greater processing demands. Since PRT did not increase between dual- and triple-task conditions, results of the present studies suggest that PRT could be measuring spare capacity, which remained relatively constant as processing demands increased. Analogous data were reported by C. D. Wickens (see record 1976-09005-001) for a triple-task situation. These observations would not have been predicted by available models of divided-attention performance. (French summary) (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Slowed reaction time during a continuous performance test in children with Tourette''s syndrome

The HRP-1 cell line is derived from normal rat placenta and appears morphologically similar to and retains characteristic expression of cellular markers of labyrinthine trophoblast cells. In this study, monolayers of HRP-1 cells grown on permeable supports were evaluated as a potential in vitro system to study trophoblast transport and metabolism. The cell line was shown to express and retain functional activity of the predominant placental cytochrome P450 isozyme, CYP1A1. Additionally, the HRP-1 cells retain functional activity of angiotensin I converting enzyme and carboxypeptidase N-like enzyme, peptidases characteristic of the trophoblast. The permeation of several hydrophilic, inert markers across the HRP-1 monolayers was observed to be dependent on effective molecular size and to be passive in nature. Functional asymmetry of the HRP-1 cells was illustrated by the predominant permeation of linoleic acid in the apical-to-basolateral direction across the monolayers. Transferrin passage across HRP-1 monolayers was concentration-dependent, was bidirectional, and could be inhibited by unlabeled transferrin, features typical of the trophoblast transport system for transferrin. Collectively, these properties suggest that the HRP-1 cell line may provide a useful tool for evaluating some of the permeability and metabolic properties of the trophoblast.     

Comparative effects of different test day challenges on performance in the 5-choice serial reaction time task.

The 5-choice serial reaction time task (5-CSRTT) is a valuable cognitive test that permits the simultaneous assessment of several different cognitive modalities, including attention, impulse control, processing speed, and cognitive flexibility. Increasing task difficulty on test days through various challenges can further enhance the versatility of this test by selectively enhancing the cognitive load on different aspects of the task. Systematic comparisons of the effects of different test day challenges on 5-CSRTT performance are essential to verify how these challenges affect different task measures and which manipulations are best suited for future studies of different aspects of cognition. We trained Wistar rats in the 5-CSRTT under standard conditions, then challenged them on the test days by (1) decreasing the duration of the stimulus to be detected, (2) increasing the time interval between trials (intertrial interval, ITI), (3) randomly varying the ITI, or (4) adding a flashing light distractor. All test day challenges produced distinct profiles of performance disruption that reflected differential effects on different cognitive modalities. Decreased stimulus duration selectively impaired attentional performance, while increased ITI increased impulsive-like premature responses and decreased trials completed. Variable ITI induced only mild, nonsignificant disruptions in response inhibition and processing speed, while the flashing light distractor produced comprehensive impairment affecting multiple aspects of 5-CSRTT performance, including disrupted attention and increased premature and timeout responses. This improved understanding of the effects of different test day challenges in the 5-CSRTT will allow researchers to use these manipulations of a valuable cognitive test to their full potential. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Response force and reaction time in a simple reaction task under time pressure

The aim of this study was to examine the effect of effort on timing and force of simple reactions. To do this, we performed an experiment, arranged like a video-game, in which these variables were measured under different time-pressure conditions. In accordance with our expectations reaction time was shorter and force amplitude larger when the time for responses was limited. These findings are discussed within the framework of Sanders' (1983) model of stress.     

Learning disabled and normal college students' performance on reaction time and speeded classification tasks.

Examined the efficiency with which 24 learning-disabled (LD [mean Wechsler Adult Intelligence Scale—Revised Full-Scale IQ 105.04]) and 24 non-learning-disabled (NLD) college students performed basic cognitive-processing tasks. A simple visual reaction time (RT) and 3 speeded classification tasks were used. Results indicate that the LD Ss were slower and more variable on the speeded classification tasks than were the NLD Ss; however, the 2 groups did not differ on the simple visual RT task. Findings suggest that the deficits in higher cognitive processing found in younger LD children persist into early adulthood. It is argued that this failure to automatize very basic subskills may relate to central nervous system (CNS) dysfunction among the LD. (34 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Timing and reaction time.

Because reaction time (RT) tasks are generally repetitive and temporally regular, participants may use timing strategies that affect response speed and accuracy. This hypothesis was tested in 3 serial choice RT experiments in which participants were presented with stimuli that sometimes arrived earlier or later than normal. RTs increased and errors decreased when stimuli came earlier than normal, and RTs decreased and errors increased when stimuli came later than normal. The results were consistent with an elaboration of R. Ratcliff's diffusion model (R. Ratcliff, 1978; R. Ratcliff & J. N. Rouder, 1998; R. Ratcliff, T. Van Zandt, & G. McKoon, 1999), supplemented by a hypothesis developed by D. Laming (1979a, l979b), according to which participants initiate stimulus sampling before the onset of the stimulus at a time governed by an internal timekeeper. The success of this model suggests that timing is used in the service of decision making. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Selective hyperthermia and reaction time

Two reaction time studies are reported in which subjects responded under conditions of selective hyperthermia. Wearing a helmet prototype, the cortical surface of the subject was thermally stressed to a level 1.11 degrees C over baseline as measured by a thermocouple placed against the tympanic membrane. In a simple choice RT task, both reaction time and response variability were decreased compared to performance in either a control or placebo condition. Latency in Neisser's visual scanning task was also shortened under conditions of this thermal stress localized in the cortical region. In both cases, there was no observed decrement in accuracy or level of performance. Enhanced human performance resulting from the maintenance of cortical temperature above the normal diurnal range is implied.     

Stage analysis of reaction time.

Stage analysis of reaction time includes the decomposition of reaction time into stages and the analysis of processing within those stages. This report reviews the analytic methodology employed in stage analysis and includes suggested improvements in this methodology. The major topics covered are the construction of models of the stage, the combination of stage models into a model of the complete reaction process, the use of process models in the decomposition of reaction time, and the use of stage models in the analysis of component stages. The methods of analysis presented are applicable to a wide range of reaction processes, including processes in which the execution of stages is not strictly serial, or in which the stage times are interdependent. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Paradoxical effects in the reaction time of schizophrenics.

"A reaction-time experiment was carried out, using lights of different intensities, to test Pavlov's suggestion that paradoxical effects are commonly found in schizophrenics. It was predicted that whereas normal persons tend to respond more quickly to more intense stimuli, schizophrenics respond more slowly to such 'ultramarginal' stimuli than to lights of weaker intensity. In 22 out of 24 chronic, nonparanoid schizophrenics, RTs to the brighter stimuli were longer than those to weaker stimuli in a first testing session but not in a second. Convalescent, shore-stay schizophrenics and normal controls showed no paradoxical effects. A tentative hypothesis to explain why the chronic patients did not show paradoxical effects on retest is proposed." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Vocal and manual reaction time estimates of interhemispheric transmission time.

Examines research designed to estimate interhemispheric transmission time (IHTT) by measuring vocal and manual RTs to laterally presented unpatterned visual stimuli. The variability reported with these measures suggests that they are invalid, although this variability may reflect differences in the procedures used. When RT procedures are differentiated on the basis of task demands, the appropriate parametric analyses are shown to have been done using simple manual RT procedures to demonstrate that they provide reliable and valid estimates of IHTT. In contrast, research using vocal or more complex manual RT procedures is not considered sufficiently comprehensive to allow determination of the reliability or validity of the measures involved. It is suggested that unresolved issues can be addressed using combined behavioral and event-related potential analyses. (69 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Foreperiod and simple reaction time.

Reviews studies of simple visual and auditory reaction processes published since W. H. Teicher (1954), with emphasis on the preparatory phase of these processes, particularly the foreperiod (FP). The 1st section consists of the analysis of actual FP variables; duration, regularity, range, distribution, and preceding FPs. The 2nd section deals with factors affecting the relation between FP and reaction time (RT): (a) the modality, intensity, probability, and duration of the warning signal and reaction stimulus (RS) and (b) the speed–accuracy trade-off. It is suggested that the S's expectancy (momentary probability of the immediate delivery of the RS) is the most important determinant of the preparation to respond to the RS at any moment during a trial and, hence, of RT. Many factors exert their influence on preparation through their effect on expectancy. Other factors have a direct influence on preparation: short-term exhaustion and fatigue, immediate arousal evoked by intense auditory stimuli, the S's stimulus criterion, the speed–accuracy trade-off, and fluctuation in motor preparedness owing to inaccuracies in the control of motor preparation. (4? p ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Heart-rate effects on human reaction time

Intra-subject rs between auditory RT and heart rate for 100 males (Mage = 55 yr.) showed RT to be independent of heart rate determined from single bears. rs were of negligible magnitude though more than a chance number were significant.     

Doubly dissociable effects of median- and dorsal-raphé lesions on the performance of the five-choice serial reaction time test of attention in rats

Six experiments examined the effects of selective median (MRN)- and dorsal (DRN)-raphé nucleus lesions on the performance of the five-choice serial reaction time task. In this test rats are required to localize brief visual stimuli presented randomly in one of five locations in approximately 30 min sessions of 100 trials. Both accuracy and latency to respond are measured, as well as the incidence of premature and perseverative responding. Selective 5-HT lesions were induced by intra-raphé infusions of 5,7-dihydroxytryptamine following pretreatment with both a noradrenergic and a dopaminergic re-uptake inhibitor. Analysis of tissue monoamine content demonstrated that the MRN lesion profoundly depleted hippocampal 5-HT (by about 90%) without affecting noradrenaline and dopamine, whereas the DRN lesion primarily depleted (by about 80%) nucleus accumbens and caudate-putamen 5-HT. Rats with 5-HT lesions of the MRN performed the task with a similar degree of accuracy to that exhibited by sham-operated controls. Although the MRN lesion did not affect the latency to respond correctly to the visual targets the lesioned animals collected the food reward significantly faster than the controls. A transient increase in the number of premature responses also resulted from this lesion. In contrast the DRN lesion produced a transient but significant increase in the accuracy of performance, and increased both the speed and the probability of responding. The similarity of the effects following global forebrain 5-HT depletion and the selective DRN lesion suggests that the 5-HT projections of the DRN rather than the MRN may play an important role in impulsive behaviour following 5-HT depletion.     

Lesions of the medial and lateral striatum in the rat produce differential deficits in attentional performance.

Excitotoxic lesions of the medial frontal cortex and anterior cingulate cortex in rats have been shown to produce dissociable impairments on a reaction time visual attention (5-choice) task. Because these cortical areas project to the medial striatal region, the authors predicted similar deficits after lesions of this striatal area compared with the lateral area. Compared with sham-operated controls, rats with quinolinic acid-induced medial striatal lesions showed all the behavioral changes associated with medial frontal cortex and anterior cingulate cortex lesions. In contrast, lateral striatal lesions produced profound disturbances in the performance of the task. Control tests showed little evidence of gross deficits in either group of rats in terms of motivation, locomotor function, or Pavlovian appetitive conditioning. These data suggest that the medial and lateral striatum have contrasting roles in the control of instrumental responding related to the primary sources of their cortical innervation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)