Focused attention deficits in patients with Alzheimer's disease and mild cognitive impairment

Reaction time (RT) tasks take various forms, and can assess psychomotor speed, (i.e., simple reaction time task), and focused attention (i.e., choice reaction time (CRT) task). If cues are provided before stimulus presentation (i.e., cued choice reaction time (CCRT) task), then a cueing effect can also be assessed. A limited number of studies have addressed the nature of focused attention impairments in Alzheimer's disease (AD). Additionally, it is unknown whether similar impairments occur in Mild Cognitive Impairment (MCI). The current study used three RT tasks to address the nature of focused attention impairments in AD and MCI subjects. The results suggest that there were significant CRT and CCRT differences in AD subjects when compared to NECs. Furthermore, slowed RTs were also present in the MCI group, which provides evidence for impaired focussed attention and the inability to benefit from a cue in both the MCI and AD groups. The implications of the impairments related to the MCI group could potentially prove useful in early diagnosis of cognitive impairments in the elderly.     

Response speed, contingent negative variation and P300 in Alzheimer’s disease and MCI

Background

Decreased speed of information processing is a hallmark of Alzheimer’s disease (AD) and mild cognitive impairment (MCI). Recent studies suggest that response speed (RS) measures are very sensitive indicators of changes in longitudinal follow-up studies. Insight into the psycho-physiological underpinnings of slowed RS can be provided by measuring the associated event-related potentials (ERP).

Aims

The current study aims to investigate the relation between RS and its psycho-physiological correlates in AD and MCI.

Methods

Fifteen psychoactive drug-naïve AD patients, 20 MCI patients and twenty age-matched, healthy control subjects participated. Response speed was measured during a simple (SRT) and choice reaction time task (CRT). An oddball and contingent negative variation (CNV) paradigm were used to elicit ERP. To evaluate test-retest reliability (TRR), subjects underwent a similar assessment one week after the first.

Results

The SRT and CRT distinguished the patient groups significantly. The P300 amplitude and latency also distinguished the groups and showed a significant correlation with response speed. The CNV amplitude did not reveal a significant difference between groups and also showed a low TRR.The TRR of the SRT, CRT and P300 amplitude and latency in general was moderate to high.The current study suggests that response speed measures on a behavioural and psycho-physiological level deserve attention as a possible marker in the diagnosis and follow-up of AD.     

Visuo-spatial working memory span: a sensitive measure of cognitive deficits in children with ADHD.

Working memory (WM) has been hypothesised to be impaired in attention-deficit/hyperactivity disorder (ADHD). However, there are few studies reported on tests measuring visuo-spatial WM (VSWM) in ADHD. Some of these studies used paradigms including episodic memory, others only used low memory loads. In the present study we used a VSWM test that has not been used previously in ADHD research. The sensitivity of the VSWM test and a choice reaction time (CRT) test was evaluated in a pilot study by comparing them to two commonly used tests in ADHD-research; the Continuous Performance Test (CPT) and a Go/no-go test, in children with and without ADHD. The groups differed significantly in performance on the VSWM test (P < .01) and CRT (P < .05) but not on the CPT (P > .1) or on the Go/no-go test (P > .1). The results from the VSWM and CRT tests were replicated in a larger sample of participants (80 boys; 27 boys with ADHD and 53 controls, mean age 11.4 years). The difference between the groups was significant for both the VSWM test (P < .01) and the CRT test (P < .01). The effect size (ES) of the VSWM test was 1.34. There was a significant age-by-group interaction on the VSWM test, with larger group differences for the older children (P < .01). Our results show that the VSWM test is a sensitive measure of cognitive deficits in ADHD and it supports the hypothesis that deficits in VSWM is a major component of ADHD.     

Interval length and time-use by children with AD/HD: a comparison of four models

Predictions made by 4 competing models of time use by children with AD/HD were tested using a computerized version of the Matching Familiar Figures Test in 2 studies. In Study 1 teacher-identified AD/HD children (N = 10) and non-AD/HD controls (N = 10) completed the task under 3 different trial duration conditions (5, 10, and 15 s). In Study 2 the same task was completed by a group of children with a diagnosis of Hyperkinetic Disorder (N = 12) and controls (N = 12). In both studies AD/HD children performed poorly on trials of both 5- and 15-s duration but as well as controls on the 10-s trials. This quadratic function provided support for the State Regulation Deficit model of time use in AD/HD. The value of tailoring the temporal features of learning contexts to the conceptual style of AD/HD children is discussed.     

Evidence for an Error Monitoring Deficit in Attention Deficit Hyperactivity Disorder

We studied error monitoring in ADHD and control children in a task requiring inhibition of a motor response. The extent of slowing following successful (stopped) and failed (nonstopped) inhibition was compared across groups. We also measured the time required to inhibit a response (stop signal reaction time, SSRT). Compared to controls, ADHD participants slowed less following nonstopped responses. Slowing did not vary with comorbid reading, oppositional, conduct or anxiety disorder, sex or ADHD subtype. Slowing after nonstopped responses was marginally, although significantly correlated with total ADHD symptoms and with age. ADHD participants had significantly longer SSRT than controls, but SSRT was not significantly correlated with slowing. The apparent deficit in error monitoring in ADHD and its independence from the inhibition deficit observed in ADHD has implications for executive control models of ADHD, performance problems associated with the disorder and for component theories of executive control.     

Visuo-Spatial Working Memory Span: A Sensitive Measure of Cognitive Deficits in Children With ADHD

Working memory (WM) has been hypothesised to be impaired in attention-deficit/hyperactivity disorder (ADHD). However, there are few studies reported on tests measuring visuo-spatial WM (VSWM) in ADHD. Some of these studies used paradigms including episodic memory, others only used low memory loads. In the present study we used a VSWM test that has not been used previously in ADHD research. The sensitivity of the VSWM test and a choice reaction time (CRT) test was evaluated in a pilot study by comparing them to two commonly used tests in ADHD-research; the Continuous Performance Test (CPT) and a Go/no-go test, in children with and without ADHD. The groups differed significantly in performance on the VSWM test (P<.01) and CRT (P<.05) but not on the CPT (P>.1) or on the Go/no-go test (P>.1). The results from the VSWM and CRT tests were replicated in a larger sample of participants (80 boys; 27 boys with ADHD and 53 controls, mean age 11.4 years). The difference between the groups was significant for both the VSWM test (P<.01) and the CRT test (P<.01). The effect size (ES) of the VSWM test was 1.34. There was a significant age-by-group interaction on the VSWM test, with larger group differences for the older children (P<.01). Our results show that the VSWM test is a sensitive measure of cognitive deficits in ADHD and it supports the hypothesis that deficits in VSWM is a major component of ADHD.     

On the relation between stimulus intensity and processing time: Piéron’s law and choice reaction time

Piéron (1914, 1920, 1952) demonstrated that simple reaction time (SRT) decays as a hyperbolic function of luminance in detection tasks. However, whether such a relationship holds equally for choice reaction time (CRT) has been questioned (Luce, 1986; Nissen, 1977), at least when the task is not brightness discrimination. In two SRT and three CRT experiments, we investigated the function that relates reaction time (RT) to stimulus intensity for five levels of luminance covering the entire mesopic range. The psychophysical experiments consisted of simple detection, two-alternative forced choice (2 AFC) with spatial uncertainty, 2 AFC with semantic categorization, and 2 AFC with orientation discrimination. The results of the experiments showed that mean RT increases with task complexity. However, the exponents of the functions relating RT to stimulus intensity were found to be similar in the different experiments. This finding indicates that Piéron’s law holds for CRT as well as for SRT. It describes RT as a power function of stimulus intensity, with similar exponents, regardless of the complexity of the task.     

Response-selection processes in paranoid and nonparanoid schizophrenia

Previous research (Marshall, 1973) has shown that the most pronounced component of deficit on a choice reaction time task among a mixed schizophrenic sample involved response-selection processes. Other evidence has indicated that paranoids may be more deficient in this respect than nonparanoids. Hence, it was hypothesized that the former subgroup of schizophrenics would display response-selection deficit while the latter subgroup would display either less or no deficit. Response-selection processes were re-examined using the CRT paradigm with comparisons carried out among paranoid and nonparanoid schizophrenics and a group of nonschizophrenic controls. Results indicated that only the paranoid schizophrenics displayed abnormally retarded response-selection operations, the nonparanoid schizophrenics being nonsignificantly discriminable from the controls. It was suggested that past evidence of CRT response-selection deficit among mixed schizophrenics might have been attributable primarily to the performance of the paranoids, whose performance appears to be adversely affected by an increase in the number of dimensions relevant to response selection.     

Additive factors analysis of reaction time with alphanumericals and line orientations as stimuli

Most additive factors method (AFM) analyses of choice reaction time (CRT) have used alphanumerics whereas tests of single process models have often used line length or line orientation. The suggestion is raised that commonly observed additive effects of variables on CRT might not apply to stimuli of the latter category. This would mean a severe limitation of the AFM in that the stage structure of choice reactions would be stimulus specific. The issue is addressed in two experiments. The first showed additive effects of stimulus quality and stimulus-response compatiblility for both alphanumerics and line orientations as stimuli. The second showed that for both stimulus categories the effect of stimulus quality was fully reflected in visual fixation time. Together the results argue against a single central process and favour a stage model of CRT.     

Driving skills of young adults with developmental coordination disorder: Maintaining control and avoiding hazards

In this study we assess for the first time the driving skills of young adults with developmental coordination disorder (DCD). We use a virtual city and a driving simulator to examine steering control, speed regulation and the responses to pedestrians on the road. Participants were adolescents and young adults who had been diagnosed with the disorder as children. For most participants the symptoms were maintained (DCD group) but for others they had largely dissipated (AD group). We also invited typically developing (control) participants matched in age, gender, and driving experience to the DCD and AD participants. Compared to their matched controls, the DCD group showed difficulties in steering when turning bends but not when driving along straight roads. Although the average speed of the DCD group was similar to their controls this may have been too fast for them to steer effectively around the bends. The DCD group also took 50% more time to react to pedestrians who walked towards their path. We found no such differences between the AD and their matched controls. We discuss the results in terms of visual information processing and suggest further applied and fundamental research on this topic.     

Relations between information processing and intelligence in elderly adults

Measures of verbal intelligence and abstract reasoning were taken on a group of 31 college-aged and 32 elderly adults, together with mental-processing rates associated with choice reaction time, primary memory scanning, and lexical decoding. Group means showed that both verbal IQ and lexical decoding were intact in the elderly subjects, a relationship in keeping with theorizing of Hunt (1978). In contrast, there were large declines in both Ravens scores and a variety of CRT measures, in keeping with theorizing of Jensen (1980). The group results were upheld at the level of individual subjects in the verbal domain, but in the case of CRT, only intercept values, not slopes, correlated with abstract reasoning. Memory-scanning rates were unrelated to intelligence measures.     

Redundancy phenomena are affected by response requirements

Results are reported for two go/no-go reaction time (RT) experiments, in which the redundant targets advantage was investigated. These experiments were replications of two earlier choice reaction time (CRT) experiments, in which letter stimuli were used. Important differences between the go/no-go RT experiments and the CRT experiments were obtained. Equal and significant redundancy advantages were obtained whether redundant targets were compared with a single target presented with a noise letter or without noise. In the CRT experiments, the advantage was not obtained in the comparison with a single target presented alone. Noise letters did not slow the RTs to single targets with which they were presented as was the case with CRT. Since the differing results of the two procedures depend on the response requirements, explanation of differing CRT data in terms of perceptual or attentional concepts is probably inappropriate. The presence and absence of response competition in the two situations may be the best interpretation. The results tend to support a conclusion of the parallel processing of two letter stimuli separated spatially by as much as 3 degrees.     

主观记忆减退老年人情节记忆的行为表现及其脑机制

情节记忆是个体对特定时间,特定地点所经历的特定事件的记忆.主观报告情节记忆下降是主观记忆减退老年人最典型的表现.与健康对照组老年人相比, 主观记忆减退老年人情节记忆下降的速率更快, 罹患老年性痴呆的风险更高, 但其情节记忆加工的脑机制尚不明确.前人研究提示, 主观记忆减退老年人在外在记忆行为尚未出现损伤的情况下, 其大脑情节记忆相关脑区的神经活动已经出现异常.探究主观记忆减退的记忆神经环路关键节点和路径的异常, 揭示神经环路在老年痴呆发生发展中的变化规律, 对深入理解老年痴呆的发病机制有重要的科学意义.同时, 主观记忆减退老年人作为特殊的记忆损伤群体, 对其神经环路的深入探究, 也必将为揭示人类记忆的神经机制做出独特的贡献.     

Distributed planning of movement sequences

Three experiments are reported that examine whether fast finger-tapping sequences are entirely planned before execution starts (advance planning), or if they can be started while planning is still under way (distributed planning). Subjects performed finger tapping sequences of three to eight taps at a high rate, under both simple and 2-choice reaction time (RT) conditions. The sequences differed in the location of an accentuated element within them. The RT to choose between sequences with different accent locations progressively decreased as an inverse function of the time-distance between the initial tap and the first point at which the alternative sequences differed. The shortening in choice reaction time (CRT) was never accompanied by noticeable changes in the inter-response times or force patterns of the tapping sequences. The RT to initiate sequences with accent location known beforehand (SRT condition) showed, in two of three experiments, a weak decreasing trend as the accentuated tap shifted away from the beginning of the sequence. The SRT results suggest a possible predominance of advance planning when the same sequence is repeated over a series of trials. The CRT results are taken as evidence that planning of the sequence beyond the unpredictable tap could be distributed before and after sequence initiation. Several factors are discussed that may influence the balance between planning in advance of, and planning in parallel with, sequence execution.     

Distributed Planning of Movement Sequences

Three experiments are reported that examine whether fast finger-tapping sequences are entirely planned before execution starts (advance planning), or if they can be started while planning is still under way (distributed planning). Subjects performed finger tapping sequences of three to eight taps at a high rate, under both simple and 2-choice reaction time (RT) conditions. The sequences differed in the location of an accentuated element within them. The RT to choose between sequences with different accent locations progressively decreased as an inverse function of the time-distance between the initial tap and the first point at which the alternative sequences differed. The shortening in choice reaction time (CRT) was never accompanied by noticeable changes in the inter-response times or force patterns of the tapping sequences. The RT to initiate sequences with accent location known beforehand (SRT condition) showed, in two of three experiments, a weak decreasing trend as the accentuated tap shifted away from the beginning of the sequence. The SRT results suggest a possible predominance of advance planning when the same sequence is repeated over a series of trials. The CRT results are taken as evidence that planning of the sequence beyond the unpredictable tap could be distributed before and after sequence initiation. Several factors are discussed that may influence the balance between planning in advance of, and planning in parallel with, sequence execution.     

事故多发驾驶员与安全驾驶员反应时的比较研究

本文对18名事故多发卡车驾驶员和18名安全卡车驾驶员的视觉、听觉简单反应时、选择反应时以及决策时间进行了比较研究.结果表明事故多发组卡车驾驶员的视觉、听觉简单反应时比安全组卡车驾驶员长,但差异不显著;事故多发组卡车驾驶员的视觉、听觉选择反应时与决策时间都比安全组卡车驾驶员长,且差异显著.本研究结果为我国深入开展驾驶员的选拔、培训与驾驶适应性检测提供理论依据与技术支持.     

What makes targets redundant?

Two letter-classification experiments that investigated target-redundancy effects on reaction time (RT) were conducted. Both experiments were replicated with choice reaction time (CRT) and go/no-go (GNG) procedures. In each experiment, there were two single-target conditions, one with a noise letter and one without. In one experiment, the letter classes were two letters that could be of either case. In the second experiment, each class consisted of two different capital letters. In both experiments, there were two redundant-targets conditions, one with identical targets and one with the different members of a class. In both of the GNG experiments, redundancy gains were obtained comparing the different-targets condition with the no-noise, single-target condition. Redundant stimuli are ones that lead to the same response. Visually different stimuli may be processed in parallel and jointly activate a response. GNG procedures are more sensitive than CRT in the investigation of redundancy effects.     

Validity Evidence for a Croatian Version of the Conditional Reasoning Test for Aggression

The Conditional Reasoning Test for Aggression (CRT‐A) is based on the idea that aggressive individuals use motive‐based cognitive biases to see their behavior as reasonable and that those biases can be measured with inductive reasoning tasks. Although the initial validation efforts for the CRT‐A in the United States have been reasonably successful, there has been no attempt to determine if the evidence of validity and reliability generalizes to other cultural contexts. In this paper, we describe four studies designed to systematically accumulate validity evidence for the CRT‐A using Croatian participants. Our analyses revealed that the Croatian adaptation of the CRT‐A yielded psychometric characteristics that were similar to those obtained on the US samples (Study 1). CRT‐A scores that predicted counterproductive work behaviors occurrence beyond self‐reported personality (Study 2) were independent from general mental ability as measured with an abstract reasoning test (Study 3), and not susceptible to faking (Study 4).     

What makes targets redundant?

Two letter-classification experiments that investigated target-redundancy effects on reaction time (RT) were conducted. Both experiments were replicated with choice reaction time (CRT) and go/no-go (GNG) procedures. In each experiment, there were two single-target conditions, one with a noise letter and one without. In one experiment, the letter classes were two letters that could be of either case. In the second experiment, each class consisted of two different capital letters. In both experiments, there were two redundant-targets conditions, one with identical targets and one with the different members of a class. In both of the GNG experiments, redundancy gains were obtained comparing the different-targets condition with the no-noise, single-target condition. Redundant stimuli are ones that lead to the same response. Visually different stimuli may be processed in parallel and jointly activate a response. GNG procedures are more sensitive than CRT in the investigation of redundancy effects.