Bilingual deep dysphasia

We report B.R.B., a bilingual Turkish-English speaker with deep dysphasia. B.R.B. shows the typical pattern of semantic errors in repetition with effects of lexicality and imageability on performance in both languages. The question we asked is whether language type (Turkish or English) or language status--that is, first acquired (L1) or second acquired (L2)--has a greater impact on performance. Results showed that repetition in L1 (Turkish) was better than that in L2 (English). We also observed effects of language status on oral reading, writing to dictation, and naming (spoken and written) with greater impairment to repetition than other tasks in both languages. An additional finding was that spoken-word translation in both directions was worse than written-word translation, and word class had an effect on translation from L1 to L2. We argue that interactive activation models of deep dysphasia could explain deep dysphasia in bilingual speakers and interactions between task and language, if the weighted connections that support language processing in L2 are assumed to be weaker, thus causing rapid phonological decay to have more impact on task performance in L2. Implications of the results for models of bilingual language processing are also considered.     

Short-term memory,working memory,and syntactic comprehension in aphasia

Sixty-one people with aphasia were tested on 10 tests of short-term memory (STM) and for the ability to use syntactic structure to determine the meanings of 11 types of sentences in three tasks—object manipulation, picture matching, and picture matching with self-paced listening. Multilevel models showed relationships between measures of the ability to retain and manipulate item and order information in STM and accuracy and reaction time (RT), and a greater relationship between these STM measures and accuracy and RT for several more complex sentence types in individual tasks. There were no effects of measures of STM that reflect the use of phonological codes or rehearsal on comprehension. There was only one effect of STM measures on self-paced listening times. There were double dissociations between performance on STM and individual comprehension tasks, indicating that normal STM is not necessary to perform normally on these tasks. The results are most easily related to the view that STM plays a facilitatory role in supporting the use of the products of the comprehension process to accomplish operations related to tasks.     

The contribution of sleep to improvements in working memory scanning speed: a study of prolonged sleep restriction

Working memory scanning and motor response speeds were assessed in chronically sleep restricted participants using the Sternberg item recognition paradigm (SIRP). Twenty-two healthy volunteers (ages 21-30) living in a controlled hospital environment were allowed either 4h of sleep opportunity (50% of habitual sleep) or 8h of sleep opportunity (100% of habitual sleep) for 12 days. Working memory scanning efficiency (time taken to access an item in working memory) was tested for the first 9 days of sleep restriction and improved over time in participants permitted an 8h sleep period, but did not change significantly in participants permitted a 4h sleep period. Speed of motor response (reaction time independent of cognitive processing) did not change significantly in either group. These results indicate that the efficiency of working memory scanning can improve with repeated practice given sufficient sleep, and that prolonged sleep restriction to 50% of habitual sleep prevents this improvement.     

阅读障碍儿童视觉记忆研究

目的 :研究阅读障碍儿童视觉短时和工作记忆能力特点。方法 :采用on -line的实验方法 ,比较小学三年级阅读障碍儿童和正常儿童对简单材料和复杂材料的视觉短时和工作记忆能力。结果 :(1 )在视觉短时记忆能力上 ,阅读障碍儿童与正常儿童不存在显著差异 ;(2 )在视觉工作记忆能力上 ,无论是对简单的视觉材料还是复杂的视觉材料 ,阅读障碍儿童都显著落后于正常儿童 ,工作记忆存在一定的落后。结论 :阅读障碍儿童视觉记忆落后主要存在于工作记忆环节     

Short-Term Memory During Stage-2 Sleep

A recently-proposed model of dream recall phenomena (Koulack & Goodenough, 1976) assumes a short-term memory store which functions during sleep, and from which either dreams or externally-delivered stimuli can be retrieved if the subject is awakened during the life of the short-term trace. To test this assumption, two experiments were designed to examine short-term memory for auditory stimuli over intervals of uninterrupted stage-2 sleep. A random series of single-digit numbers was presented at the rate of one every 30 sec throughout the night, at an intensity slightly above normal conversational levels. Subjects habituated to the sound and did not awaken spontaneously. Experimental awakenings took place either at 1 sec (Experiment 1) or at 1, 5, or 10 sec (Experiment 2) after selected target stimuli, and the subjects were asked to recall which number they had heard. Significant recall was obtained over intervals of up to 10 sec, and the likelihood of recall was inversely related to reaction times to the awakening stimulus. Repeating the target numbers at 30-sec intervals increased EEG alpha activity and K-complex amplitude, suggesting that some form of trace persists for at least 30 sec.     

Maintenance of tactile short-term memory for locations is mediated by spatial attention

According to the attention-based rehearsal hypothesis, maintenance of spatial information is mediated by covert orienting towards memorized locations. In a somatosensory memory task, participants simultaneously received bilateral pairs of mechanical sample pulses. For each hand, sample stimuli were randomly assigned to one of three locations (fingers). A subsequent visual retro-cue determined whether the left or right hand sample was to be memorized. The retro-cue elicited lateralized activity reflecting the location of the relevant sample stimulus. Sensory processing during the retention period was probed by task-irrelevant pulses randomized to locations at the cued and uncued hand. The somatosensory N140 was enhanced for probes delivered to the cued hand, relative to uncued. Probes presented shortly after the retro-cue showed greatest attentional modulations. This suggests that transient contributions from retrospective selection overlapped with the sustained effect of attention-based rehearsal. In conclusion, focal attention shifts within tactile mnemonic content occurred after retro-cues and guided sensory processing during retention.     

Imitation of novel and well-known actions

Four experiments were carried out using the action span paradigm. In experiment 1 we found that well-learnt, meaningful (MF) actions were imitated better than novel, meaningless (ML) actions. In experiments 2 and 3, during the encoding of MF and ML actions, participants were required to carry out different suppression tasks. In experiment 2 we replicated the advantage of MF actions over ML actions and also found that the motor suppression shortened the action span more than the other forms of suppressions (spatial and articulatory). Action encoding and motor suppression tapping the same subsystem, temporarily holding the motor information, could explain the reduced motor span obtained in experiment 2. Two alternative explanations that could have accounted for this effect were ruled out in experiments 3 and 4. In experiment 3 we verified whether the reduction of the action span was produced by the different combination of the articulatory suppression with motor suppression or with the spatial suppression. In experiment 4, we demonstrated that the reduction was not due to the motor suppression being more difficult than the other types of suppression. The critical finding that the spans of well-learnt, MF actions are longer than those of novel, ML actions observed in experiments 1 and 2 was interpreted in terms of different processing routes engaged in the imitation of these two types of actions. MF actions can be imitated along both a semantic, indirect route and a direct route leading from the visual analysis of the action to the motor system. In contrast, the imitation of ML actions is accomplished along the direct route only.     

学习障碍儿童记忆的比较研究 Ⅰ.学习障碍儿童的短时记忆和工作记忆

目的：考查学习障碍儿童的短时记忆和工作记忆及各型学习障碍儿童短时记忆特征，比较短时记忆和工作记忆对学习的相对贡献。方法：根据儿童的学科成绩、智力水平、教师对学习能力的评定，结合临床观察，从三所小学１５６４名学生中筛查出学习障碍儿童９７人（男７１人，女２６人），正常学习儿童６３人（男３６，女２７人），并根据主要困难所在把学习障碍儿童分为三组：语文障碍（３１人）、数学障碍（２１人）和混合型障碍（４５人）。对每个入组儿童作个别记忆测查，内容包括短时记忆（数字、汉词和符号）和工作记忆（数字、汉词、符号、故事）。结果：混合型障碍的短时记忆和工作记忆均低于对照组，语文障碍对言语材料的短时记忆和工作记忆中的故事理解低于对照组，数学障碍仅言语材料的短时记忆低于对照组；三型学习障碍之间仅在数字广度和故事Ⅱ阅读理解二项任务上有差异；短时记忆和工作记忆与学习成绩均有中度相关，工作记忆与数学成绩的相关更高。结论：学习障碍儿童存在共同的短时记忆和工作记忆缺陷，但缺陷程度有差异，这种缺陷可能与言语编码缺陷或记忆系统本身功能障碍有关。     

Genetic Covariance Structure of Reading,Intelligence and Memory in Children

This study investigates the genetic relationship among reading performance, IQ, verbal and visuospatial working memory (WM) and short-term memory (STM) in a sample of 112, 9-year-old twin pairs and their older siblings. The relationship between reading performance and the other traits was explained by a common genetic factor for reading performance, IQ, WM and STM and a genetic factor that only influenced reading performance and verbal memory. Genetic variation explained 83% of the variation in reading performance; most of this genetic variance was explained by variation in IQ and memory performance. We hypothesize, based on these results, that children with reading problems possibly can be divided into three groups: (1) children low in IQ and with reading problems; (2) children with average IQ but a STM deficit and with reading problems; (3) children with low IQ and STM deficits; this group may experience more reading problems than the other two. Edited by Chandra Reynolds.     

Short duration of retroactive facilitation of social recognition in rats

Adult rats spent less time investigating the same juvenile during a second dyadic encounter session. This decrease served as an index for social recognition. Social recognition was not influenced by isolating the juveniles for 7 days prior to experimentation. Retroactive facilitation of social recognition was observed when the two rats were confronted for a longer period of time on a given day by multiple testing. However, this facilitation was not observed after a 24-h interexposure interval between encounter sessions, even when different housing conditions during that time were taken into account, and animals were tested during 5 consecutive days. It is suggested that social recognition may be a form of short-term memory.     

Reduction of ECS produced retrograde amnesia by post-trial introduction of strychnine

Strychnine sulfate was used to reduce the amount of retrograde amnesia induced by electroconvulsive shock (ECS). Male Swiss-Webster mice were trained on the step-down passive avoidance task, given ECS and then injected intraperitoneally with either 0.1 mg/kg strychnine or saline. The animals were tested in the apparatus one to twenty-four hours later. Mice given ECS alone displayed partial memory for the training (by responding with longer latencies) if tested within two hours after training, but did not display retention twenty-four hours later. Animals given strychnine following ECS had significantly longer step-down latencies at twenty-four hours than did the saline or no injection controls. Further experiments replicated the basic results, and also showed that strychnine injections delayed two hours after the training trial attenuated ECS-induced retrograde amnesia, but that a three hour injection delay was ineffective. The results were interpreted in terms of changes in short-term and long-term memory.     

Long-term memory is the representational basis for semantic verbal short-term memory

The present study supports activation models of verbal short-term memory that include a semantic contribution to the retention process. Event-related brain potentials were used to probe the level of activation of semantic representations of a series of words in a delay interval following their presentation. The levels of activation were compared in two tasks: (1) a short-term memory task that involved a semantic judgment in the recall phase following the delay interval, and (2) a nonmemory control task. The level of semantic activation during the delay interval was higher in the short-term memory task, indicating that enhanced activation of semantic representations is involved in the short-term storage of verbal information. This result implies that activated long-term memory provides a representational basis for semantic verbal short-term memory, and hence supports theories that postulate that short- and long-term stores are not separate.     

Exposure to extremely low-frequency electromagnetic fields improves social recognition in male rats

The effect of exposure to low-frequency electromagnetic fields (ELF EMFs) on social recognition was studied. The test was based upon a comparison between two encounters of an adult rat and a conspecific juvenile, separated by an interexposure interval (IEI). The exposure to ELF EMF of 1 mT intensity during 2 h for 9 days increased the duration of short-term memory of adult male Wistar rats up to 300 min. These data indicate, for the first time, that ELF EMF improves social recognition memory in rats.     

Effects of electrical stimulation of rat limbic system and midbrain reticular formation upon short- and long-term memory

Rats were given electrical stimulation of the midbrain reticular formation, hippocampus or amygdala 4 sec after receiving a footshock contingent upon a barpress response. They were retested for memory of the shock 64 sec or 24 hr after the footshock. The animals that received midbrain reticular formation stimulation showed amnesia at 64-sec retest and memory at 24-hr retest. In contrast, animals that received hippocampal brain stimulation showed memory at 64-sec retest and amnesia at 24-hr retest. Animals that received amygdala brain stimulation showed amnesia at both 64-sec and 24-hr retest. The data support a dual parallel processing model of memory.     

Prefrontal, parietal and basal activation associated with the reordering of a two-element list held in working memory

A functional specialization in the prefrontal cortex along a dorsal-ventral gradient according to the type of processing in working memory, i.e. manipulation vs. maintenance, has been proposed based on previous neuroimaging studies. This seems particularly important for the further understanding of the functional architecture underlying working memory problems in patient populations. The current study examines the prefrontal involvement in the maintenance and manipulation of serial order of elements in working memory, with a task designed to be as simple as possible, to the aim of possible uses in clinical studies. Subjects held two-element ordered lists in memory and were presented with pseudo-random sequences of “reorder” and “maintain” cues. Reorder cues were found to be associated with activation in the dorsal prefrontal cortex, parietal cortex and the basal ganglia. The results show that the simple task was indeed sufficient to evoke the prefrontal activation of interest, add to the information on functional dorsal-ventral specialization in prefrontal cortex and provide support for a prefrontal-parietal monitoring-manipulation network.     

Confrontation of PDP models and dual-route models through the analysis of a case of deep dysphasia

Abstract

A case study is presented of a patient, EA, who demonstrated all the defining features of deep dysphasia. His repetition disorder was associated with surface dyslexia and deep dysgraphia. EA also showed a severely restricted phonological STM. His performance in both picture confrontation naming and writing-to-dictation paralleled his performance in repetition, whereas reading aloud and oral lexical decision were not influenced by the imageability of the word input. Further testing indicated that EA did not have difficulty in either perceiving or semantically processing spoken words. An exhaustive investigation of EA's cognitive functioning was first conducted by reference to Patterson and Shewell's model (1987). Such a triple-route model can account for EA's overall performance by postulating multiple functional lesions. We alternatively show that EA's language profile could be accounted for within a highly interactive model of language processing incorporating most basic principles of connectionist-PDP models. Within this latter framework, deep dysphasia, surface dyslexia, and deep dysgraphia could be interpreted as originating from a single functional deficit. Our analysis further suggests an impact of semantic and orthographic knowledge on phonological processing.     

Alteration of working memory but not in anxiety or stress response in p300/CBP associated factor (PCAF) histone acetylase knockout mice bred on a C57BL/6 background

P300/CBP associated factor (PCAF) acts as an acetyltransferase that acetylates specific lysine residues in histones, thereby remodelling chromatin structure. The possible involvement of PCAF in learning and memory processes or mood disorders was recently assessed by characterizing the behavioural phenotype of PCAF KO mice bred on a CD1 background and revealed short-term memory deficits that evolved with age towards long-term memory alteration and an exaggerated response to stress [10]. PCAF KO mice have been backcrossed on a C57BL/6j strain for 15 generations and we report here the first data regarding their behavioural phenotype. PCAF KO mice bred on a C57 background showed short-term memory deficits in terms of decreased spontaneous alternation and absence of acquisition of a daily changing platform position in the water-maze. Acquisition of a fixed platform location or passive avoidance response was preserved. PCAF KO mice showed no difference with WT C57BL/6j controls in their performances in the forced swimming and light/dark exploration box, suggesting no particular phenotype on anxiety and stress responses. We therefore evidenced marked phenotypic differences in PCAF KO mice depending on the genetic background strain confirming that PCAF histone acetyltransferase is involved lifelong in the chromatin remodelling necessary for memory formation but differentially involved in anxiety and response to stress.     

Selective impairment in visual short-term memory binding

Dissociations within binding in perception have been reported after brain damage. In short-term memory (STM), feature binding and feature processing appear to rely on separate processes. However, dissociations within binding in STM following brain damage have not been reported to date. We report on the case E.S. who, after removal of a left medial sphenoid ridge meningioma, developed a selective impairment of visual STM (VSTM) binding. We found that, despite having normal perceptual binding, E.S. was unable to retain in VSTM features bound into objects while she could retain individual features as well as controls did (Experiments 1–2, 4, and 6). Her verbal STM for bound and single features remains intact (Experiments 3 and 5). E.S.'s performance suggests that STM binding can be dissociated from STM for single features across visual and verbal domains. The results are discussed in the light of current models of STM.     

Visual encoding differentially affects auditory event-related potentials during working memory retrieval

Previous working memory studies using auditory stimuli at both encoding and retrieval show amplitude decreases in event-related potentials (N100 and late positive wave, LPW) at retrieval as a function of memory load. This study tested if these effects are associated with phonological or semantic coding by presenting visual stimuli at encoding and auditory stimuli at retrieval. We hypothesized that event-related potentials associated with phonological but not semantic coding would be affected by modality differences at encoding and retrieval. Memory sets having one, three, or five visual digits were followed by auditory probes that subjects classified as present or absent from the set. Reaction time increased and LPW amplitudes decreased with increases in memory load, but there were no significant effects of memory load on N100 amplitude. Results suggest that with respect to brain activity that covaries with memory load, probe N100 amplitude is associated with phonological coding and LPW amplitude is associated with semantic coding.