Simulating episodic memory deficits in semantic dementia with the TraceLink model

Although semantic dementia is primarily characterised by deficits in semantic memory, episodic memory is also impaired. Patients show poor recall of old autobiographical and semantic memories, with better retrieval of recent experiences; they can form new memories, and normal performance on pictorial recognition memory has been demonstrated. As these abnormalities in episodic memory are virtually a mirror image of those seen in the amnesic syndromes, semantic dementia poses a challenge to extant models of remote memory and amnesia. Here, we show that one such model, TraceLink, can reproduce some of the principal findings on episodic memory in semantic dementia. A loss of nodes and connections within the trace system, which can be identified with the temporal neocortical memory storage sites implicated in semantic dementia, simulates without further assumptions the findings reported above.     

高考数学试卷多维项目反应理论的分析及应用

高考数学学科试卷的试题综合性较强,一道试题通常考查多种能力属性,而基于单维性假设下的经典测量理论和传统的项目反应理论无法完成该种情形下试卷测量性能分析和考生作答表现分析.本文以MIRT理论为基础,使用CONQUEST软件为工具进行分析,可以获得试卷内部不同能力维度之间的相关以及考生不同维度的能力参数,为提升命题质量和改进教学提供了依据,表明MIRT具有很好的应用前景.由于MIRT理论的复杂性以至于目前分析软件的不足制约其进一步的深入应用,这是今后应该深入研究的问题.     

A Bayesian psychophysical model for angular variables

Bayesian theories of perception provide a link between observed response distributions and theoretical constructs from Bayesian decision theory. Using Bayesian psychophysics we derive response distributions for two cases, one based on a normal distribution and one on a von Mises distribution for angular variables. Interestingly, where the theoretical response distribution is always unimodal in the case of normal distributions, it can become bimodal in the angular setting in the case when prior and likelihood are about equally strong.     

Impulsive Responses In Children with Conduct Disorder and Borderline Intellectual Functioning

The study is designed to investigate response inhibition in children with conduct disorder and borderline intellectual functioning. To this end, children are compared to a normal peer control group using the Alertness test. The test has two conditions. In one condition, children are instructed to push a response button after a visual “go” signal is presented on the screen. In a second condition the “go” signal is preceded by an auditory signal, telling the child that a target stimulus will occur soon. Compared to the control group, the group carrying the dual diagnosis made many preliminary responses (responses before the presentation of the “go” signal), especially in the condition with an auditory signal. This impulsive response style was controlled for attention deficit/hyperactivity disorder characteristics of the children.     

Cognitive Control in Children with ADHD-C: How efficient are they?

The literature on children with attention deficit/hyperactivity disorder, combined type (ADHD-C), is currently inconclusive as to the nature of deficits in two forms of cognitive control — interference control and response selection (Nigg, 2006 Nigg, J. T. 2006. What Causes ADHD? Understanding what goes wrong and why, New York: The Guildford Press.  [Google Scholar]). This paper examined the performance of children with ADHD-C on interference control and response selection conflict tasks that required both speed and accuracy. The data was analyzed utilizing a new efficiency method to more effectively analyze overall responses. Both interference control and response selection conditions were combined within tasks allowing for a closer comparison of how children with ADHD-C perform on these specific types of cognitive control. Computerized tasks were administered to 62 boys, ages 7 to 12 (31 controls, 31 ADHD-C). Results revealed deficits in efficient performance for children with ADHD-C on interference control tasks and response selection tasks hypothesized to involve high cognitive control demand. These results highlight the utility of analyzing efficiency data to identify deficits in performance for children with ADHD-C and to foster an increased understanding of cognitive control functioning in this clinical population.     

Circuits and circumstances: the neurobiological consequences of early relationship experiences and how they shape later behaviour

The last decade has seen a vast increase in knowledge of how the human brain develops. It has been demonstrated that both the establishment of synaptic connections between neurones and the programming of neurochemical responses that have an effect on the whole body are dependent on experience. The most sensitive period for brain growth, the time of optimal plasticity, is over the first two or three years of life. If the baby's neurological development is threatened by abuse or neglect, which includes excessive attachment disruption, the damage may set its stamp on the rest of life.     

Response inhibition and avoidance of virtual obstacles during gait in healthy young and older adults

Adjustments of preplanned steps are essential for fall avoidance and require response inhibition. Still, inhibition is rarely tested under conditions resembling daily living. We evaluated the ability of young and older adults to modify ongoing walking movements using a novel precision step inhibition (PSI) task combined with an auditory Stroop task.Healthy young (YA, n = 12) and older (OA, n = 12) adults performed the PSI task at 4 individualized difficulty levels, as a single and dual task (DT). Subjects walked on a treadmill by stepping on virtual stepping stones, unless these changed color during approach, forcing the subjects to avoid them. OA made more failures (40%) on the PSI task than YA (16%), but DT did not affect their performance. In combination with increased rates of omitted Stroop task responses, this indicates a “posture first” strategy. Yet, adding obstacles to the PSI task significantly deteriorated Stroop performance in both groups (the average Stroop composite score decreased by 13% in YA and 27% in OA). Largest deficit of OA was observed in rates of incorrect responses to incongruent Stroop stimuli (OA 35% and YA 12%), which require response inhibition. We concluded that the performance of OA suffered specifically when response inhibition was required.     

Preparing fingers within and between hands: Examining the maximal preparation benefit in older age

Previous research has demonstrated an age-related deficit in the preparation of finger responses. A key question is whether the age-related deficit reflects differences in speed of preparation or differences in the maximal preparation benefit that can be attained given sufficiently long preparation intervals. The present study examined this issue by asking a group of younger and older adults to perform the finger-cueing task with four, relatively long, preparation intervals that varied randomly across trials. Reaction time results demonstrated that older adults were deficient in preparing two fingers on two hands at the two shortest preparation intervals, but not at the two longest ones. This outcome suggests that, with randomised preparation intervals, older adults require more time than younger adults to achieve the maximal level of between-hands preparation.     

Conflict adaptation is reflected by response interference

The conflict monitoring theory suggests that the occurrence of conflict in previous trials leads to a reduction in interference in current trials through conflict adaption. The present study included two experiments that used a colour-based flanker task and a Stroop task in combination with a 2:1 stimulus-to-response mapping manipulation and a crossing of transition types (Previous trial type×Current trial type) with stimuli to investigate conflict adaption in relation to stimulus and response interference. The results demonstrate that response interference, but not stimulus interference, was reduced following both stimuli and response conflicts in previous trials. In contrast to some recent evidence, we conclude that conflict adaptation is limited to response interference.     

Response preparation with anticues in children and adults

We examined the ability of children (mean age: 10.4 years) and adults (mean age: 20.7 years) to prepare finger keypress responses in an anticue paradigm by presenting left and right spatial cues, which specified right and left hand finger responses, respectively. Four time intervals separated cue onset from target onset: 200 ms, 600 ms, 1000 ms, and 2000 ms. Results showed that, overall, children responded slower and less accurately than did adults; nevertheless they were equally effective in using anticue information to reduce reaction time with preparation intervals of 600 ms and longer. This outcome is discussed in terms of a slow, voluntary, top-down executive process that redirects motor preparation from the ipsi- to the contralateral hand. The absence of an age effect suggests an early maturation of the underlying neural mechanisms.