P300 Latency Correlates with Digit Span

P300 latency from a simple auditory discrimination counting task was obtained along with a digit span memory task for a large group of neurologically normal subjects. Moderate significant negative correlations between the peak latency of the P3a and P3b subcomponents and total memory score were found, although no relationship was observed for other waveform component latencies and memory score. The data suggest that the P300 component of the event-related brain potential may index individual variations in memory ability.     

成人数字、词语和视空间工作记忆广度的发展特征及影响因素

目的:考察成人(18~49岁)数字、词语和视空间工作记忆广度发展变化的趋势及其影响因素。方法:采用多维记忆评估量表中的3个工作记忆广度分测验对280名正常成人进行测查,并收集一般资料。结果:成人的数字、词语和视空间广度成绩随年龄的增长均呈下降趋势(F=2.96~6.87,P<0.01);出现随龄衰减现象的先后顺序依次为视空间广度、词语广度和数字广度;在记忆广度总成绩和大多数分测验成绩上男女无显著差异,仅在30-34岁年龄组,男性视空间广度位置的成绩好于女性(11.02±3.17/8.67±3.18,t=2.15,P<0.05)。逐步回归分析结果显示,教育是成人数字、词语和视空间广度的保护因素(Beta值=0.546,0.445,0.423;P<0.01)。结论:成人阶段数字、词语和视空间工作记忆广度的发展变化基本上趋于一致,并且受教育程度能对不同的工作记忆广度起促进作用。     

The Roles of Verbal Short-Term Memory and Working Memory in the Acquisition of Grammar by Children With Williams Syndrome

The roles of verbal short-term and working memory were examined in a sample of children with Williams syndrome (mean chronological age 10 years, 2 months) and a sample of grammar-matched children who are developing normally. Forward digit span, nonword repetition, and backward span were all found to be correlated with receptive grammatical ability in the sample of children with Williams syndrome, but not in the sample of children who are developing normally. The relation between working memory, as measured by backward digit span, and grammatical ability was found to be significantly stronger in children with Williams syndrome than in the control group. This finding highlights the possibility that children with Williams syndrome may rely on their working memory to a greater extent than children who are developing normally to learn grammar. Hierarchical regression analyses indicated receptive vocabulary may mediate the relations among forward digit span, backward digit span, and grammatical ability for the children with Williams syndrome. Phonological short-term memory, however, contributed independently to grammatical ability even after receptive vocabulary was taken into account.     

The roles of verbal short-term memory and working memory in the acquisition of grammar by children with Williams syndrome

The roles of verbal short-term and working memory were examined in a sample of children with Williams syndrome (mean chronological age 10 years, 2 months) and a sample of grammar-matched children who are developing normally. Forward digit span, nonword repetition, and backward span were all found to be correlated with receptive grammatical ability in the sample of children with Williams syndrome, but not in the sample of children who are developing normally. The relation between working memory, as measured by backward digit span, and grammatical ability was found to be significantly stronger in children with Williams syndrome than in the control group. This finding highlights the possibility that children with Williams syndrome may rely on their working memory to a greater extent than children who are developing normally to learn grammar. Hierarchical regression analyses indicated receptive vocabulary may mediate the relations among forward digit span, backward digit span, and grammatical ability for the children with Williams syndrome. Phonological short-term memory, however, contributed independently to grammatical ability even after receptive vocabulary was taken into account.     

The Roles of Verbal Short-Term Memory and Working Memory in the Acquisition of Grammar by Children With Williams Syndrome

The roles of verbal short-term and working memory were examined in a sample of children with Williams syndrome (mean chronological age 10 years, 2 months) and a sample of grammar-matched children who are developing normally. Forward digit span, nonword repetition, and backward span were all found to be correlated with receptive grammatical ability in the sample of children with Williams syndrome, but not in the sample of children who are developing normally. The relation between working memory, as measured by backward digit span, and grammatical ability was found to be significantly stronger in children with Williams syndrome than in the control group. This finding highlights the possibility that children with Williams syndrome may rely on their working memory to a greater extent than children who are developing normally to learn grammar. Hierarchical regression analyses indicated receptive vocabulary may mediate the relations among forward digit span, backward digit span, and grammatical ability for the children with Williams syndrome. Phonological short-term memory, however, contributed independently to grammatical ability even after receptive vocabulary was taken into account.     

Alpha‐band desynchronization reflects memory‐specific processes during visual change detection

Recent work investigating physiological mechanisms of working memory (WM) has revealed that modulation of alpha and beta frequency bands within the EEG plays a key role in WM storage. However, the nature of that role is unclear. In the present study, we examined event‐related desynchronization of alpha and beta (α/β‐ERD) elicited by visual tasks with and without a memory component to measure the impact of a WM demand on this electrophysiological marker. We recorded EEG from 60 healthy participants while they completed three variants on a typical change detection task: one in which participants passively viewed the sample array, passive (WM?); one in which participants viewed and attended the sample array in search of a target color but did not memorize the colors, active (WM?); and one in which participants encoded, attended to, and memorized the sample array, active (WM+). Replicating previous findings, we found that active (WM+) elicited robust α/β‐ERD in frontal and posterior electrode clusters and that α‐ERD was significantly associated with WM capacity. By contrast, α/β‐ERD was significantly smaller in the passive (WM?) and active (WM?) tasks, which did not consistently differ from one another. Furthermore, no such relationship was observed between WM capacity and desynchronization in the passive (WM?) or active (WM?) tasks. Taken together, these results suggest that α‐ERD during memory formation reflects a memory‐specific process such as consolidation or maintenance, rather than serving a generalized role in perceptual gating or engagement of attention.     

Age-Associated Memory Changes in Adults With Williams Syndrome

Age-associated changes on measures of episodic and working memory were examined in 15 adults with Williams Syndrome (WS; M age = 48.3 years, SD = 14.7; M IQ = 62.9, SD = 8.5) and their performance was compared to that of 33 adults with mental retardation (MR) with unspecified etiologies (M age = 54.2 years, SD = 8.9; M IQ = 61.7, SD = 6.5). Among the group with WS, older adults were significantly poorer than younger adults on the free recall task, a measure of episodic memory. Although this finding is consistent with normal aging, it occurred at a chronologically early age in adults with WS and was not found in their peers with unspecified MR. Although both groups showed small declines with age on a backward digit span task, a measure of working memory, for the group with WS the rate of decline on backward digit span was slower as compared to their performance on the free recall task. The findings from this study indicate a chronologically early and precipitous age-associated decrease in long-term, episodic memory in adults with WS.     

Isolating the neural mechanisms of age-related changes in human working memory

Working memory (WM), the process by which information is coded into memory, actively maintained and subsequently retrieved, declines with age. To test the hypothesis that age-related changes in prefrontal cortex (PFC) may mediate this WM decline, we used functional MRI to investigate age differences in PFC activity during separate WM task components (encoding, maintenance, retrieval). We found greater PFC activity in younger than older adults only in dorsolateral PFC during memory retrieval. Fast younger subjects showed less dorsolateral PFC activation during retrieval than slow younger subjects, whereas older adults showed the opposite pattern. Thus age-related changes in dorsolateral PFC and not ventrolateral PFC account for WM decline with normal aging.     

Age-associated memory changes in adults with williams syndrome

Age-associated changes on measures of episodic and working memory were examined in 15 adults with Williams Syndrome (WS; M age = 48.3 years, SD = 14.7; M IQ = 62.9, SD = 8.5) and their performance was compared to that of 33 adults with mental retardation (MR) with unspecified etiologies (M age = 54.2 years, SD = 8.9; M IQ = 61.7, SD = 6.5). Among the group with WS, older adults were significantly poorer than younger adults on the free recall task, a measure of episodic memory. Although this finding is consistent with normal aging, it occurred at a chronologically early age in adults with WS and was not found in their peers with unspecified MR. Although both groups showed small declines with age on a backward digit span task, a measure of working memory, for the group with WS the rate of decline on backward digit span was slower as compared to their performance on the free recall task. The findings from this study indicate a chronologically early and precipitous age-associated decrease in long-term, episodic memory in adults with WS.     

Memory in learning disabled children: Digit span and the Rey auditory verbal learning test

Scores on the Rey Auditory Verbal Learning Test (RAVLT) were compared to WISC-R digit span results in a sample of 153 learning disabled students. With statistical controls for age and IQ, regression analyses indicated no significant relationships between the RAVLT and longest forward span, longest backward span and total digit span raw score. Factor analysis of the RAVLT variables, forward span, backward span and total digit span raw score yielded three factors that were interpreted to represent a long term memory factor, a short-term memory factor with high coding demands and a short-term memory factor with low coding demands. Conclusions were made regarding the inadequacy of using only digit span when making diagnostic statements about the auditory memory functioning of learning disabled students.     

Effects of 42 hr of total sleep deprivation on component processes of verbal working memory

The current investigation examined changes in working memory (WM) component processes following total sleep deprivation (TSD) in a sample of healthy young persons. Forty subjects were administered a verbal form of a continuous recognition test (CRT) before and after 42 hr of TSD. Parameters of a computational model of the CRT reflecting attention, WM span, and rate of episodic memory encoding were estimated for each individual. Subjects made more errors on the test following sleep deprivation. Analysis of model parameters revealed statistically independent declines in both the attention and WM span parameters, with a larger effect observed for the decline in WM span. Examination of individual profiles suggested that the effects of TSD on verbal WM component processes vary from person to person. Declines in global verbal WM functioning appear to be primarily driven by reduced WM span and attention; however, these effects may be individual-specific. Further applications of the computational model for examining WM component processes with sleep deprivation and other clinical populations are discussed.     

Are Smarter Brains Running Faster? Heritability of Alpha Peak Frequency, IQ, and Their Interrelation

It has often been proposed that faster central nervous system (CNS) processing amounts to a smarter brain. One way to index speed of CNS processing is through the assessment of brain oscillations via electroencephalogram (EEG) recordings. The dominant frequency (peak frequency) with which neuronal feedback loops in an adult human brain oscillate in a relaxed state is around 10 cycles/sec, but large individual differences exist in peak frequencies. Earlier studies have found high peak frequencies to be associated with higher intelligence. In the present study, data from 271 extended twin families (688 participants) were collected as part of a large, ongoing project on the genetics of adult brain function and cognition. IQ was assessed with the Dutch version of the Wechsler Adult Intelligence Scale (WAIS-IIIR), from which four dimensions were calculated (verbal comprehension, working memory, perceptual organization, and processing speed). Individual peak frequencies were picked according to the method described by Klimesch (1999) and averaged 9.9 Hz (SD 1.01). Structural equation modeling indicated that both peak frequency and the dimensions of IQ were highly heritable (range, 66% to 83%). A large part of the genetic variance in alpha peak frequency as well as in working memory and processing speed was due to nonadditive factors. There was no evidence of a genetic correlation between alpha peak frequency and any of the four WAIS dimensions: Smarter brains do not seem to run faster.     

Memory span development in Down's syndrome,severely subnormal and normal subjects

The development of digit span was studied in relation to mental age in two large groups of severely subnormal (SSN) individuals, one diagnosed as suffering from Down's syndrome and the other of mixed aetiology, and a group of normal subjects matched for mental age. Digit span in the Down's syndrome and SSN mixed aetiology groups was generally lower than that expected on the basis of mental age. A cross-sectional and longitudinal study showed a failure of development of digit span in both SSN groups which resulted in an increasing lag between digit span and mental age as mental age increased. Some possible explanations for the lack of short-term memory development in Down's syndrome and other SSN subjects are discussed, together with the possible implications of this for other aspects of cognitive development.     

Verbal working memory‐related neural network communication in schizophrenia

Impaired working memory (WM) in schizophrenia is associated with reduced hemodynamic and electromagnetic activity and altered network connectivity within and between memory‐associated neural networks. The present study sought to determine whether schizophrenia involves disruption of a frontal‐parietal network normally supporting WM and/or involvement of another brain network. Nineteen schizophrenia patients (SZ) and 19 healthy comparison subjects (HC) participated in a cued visual‐verbal Sternberg task while dense‐array EEG was recorded. A pair of item arrays each consisting of 2–4 consonants was presented bilaterally for 200 ms with a prior cue signaling the hemifield of the task‐relevant WM set. A central probe letter 2,000 ms later prompted a choice reaction time decision about match/mismatch with the target WM set. Group and WM load effects on time domain and time‐frequency domain 11–15 Hz alpha power were assessed for the cue‐to‐probe time window, and posterior 11–15 Hz alpha power and frontal 4–8 Hz theta power were assessed during the retention period. Directional connectivity was estimated via Granger causality, evaluating group differences in communication. SZ showed slower responding, lower accuracy, smaller overall time‐domain alpha power increase, and less load‐dependent alpha power increase. Midline frontal theta power increases did not vary by group or load. Network communication in SZ was characterized by temporal‐to‐posterior information flow, in contrast to bidirectional temporal‐posterior communication in HC. Results indicate aberrant WM network activity supporting WM in SZ that might facilitate normal load‐dependent and only marginally less accurate task performance, despite generally slower responding.     

Catechol O-methyl transferase and dopamine D2 receptor gene polymorphisms: evidence of positive heterosis and gene-gene interaction on working memory functioning

The COMT Val(108/158)Met polymorphism has been extensively studied in relation to individual differences in working memory (WM) performance. The present study tested the association of the COMT Val(108/158)Met polymorphism with WM performance in two independent family-based Dutch samples: 371 children (mean age 12.4 years) and 391 adults (mean age 36.2 years). A significant association was found between the COMT polymorphism and WM scores in the combined adult and young cohorts. The association reflected positive heterosis such that the Met/Met and Val/Val homozygotes did not perform as well as the Met/Val heterozygotes on the WM tasks. A secondary analysis was conducted in which a DRD2-tagging SNP (rs2075654) was tested for an interactive effect with the COMT polymorphism on WM performance. A significant interactive effect of the DRD2 and COMT genes was found such that heterosis was present only in the DRD2 genotype that has been linked to lower receptor density. Our results support previous findings that WM performance needs an optimal level of dopamine signaling within the PFC. This optimum level depends on enzymatic activity controlling dopamine level as well as dopamine receptor sensitivity, both of which may differ as a function of age and genotype. We conclude that the effects of a single polymorphism in a dopaminergic gene on a well-defined cognitive trait may easily remain hidden if the interaction with age and other genes in the pathway are not taken into account.     

The relationship between P3 and neuropsychological function in an adult life span sample

The relationship of P3 to age and neuropsychological performance was investigated in a sample of 71 well-functioning adults ranging in age from 21.8 to 94.7 years. ERPs were recorded while the participants performed an auditory two-stimuli oddball task in which the rare tones were to be counted. The Wechsler Abbreviated Scale of Intelligence (WASI) and the digit span subtest from the Wechsler Adult Intelligence Scale-R (WAIS-R) were administered. Regression analyses showed significant, linear effects of age on P3 latency and amplitude. Significant relationships between P3 and neuropsychological measures were found, in that P3 latency correlated moderately in predictable ways with scores on matrices, block design, and digit span. Overall, these relationships are best characterized by a linear function, but a non-linear component is involved in the relationship between P3 latency and fluid tests. Finally, a linear relationship between ERP components and age was found, while a curvilinear relationship was found between age and block design and matrices, respectively. There appears to be either partially different functions or structures underlying performance on these tests, the P3 component and performance on neuropsychological tests, or one must assume some variant of a multiplicative, as opposed to an additive, model of cognition.     

Normal variation of P300 in children: age, memory span, and head size

The P300 (P3) event-related brain potential was elicited in a group of 50 children and young adults (4-20 years). A simple auditory task was employed in which subjects indicated with a finger movement when a randomly occurring target tone (high pitch) was presented in a series of standard (low pitch) tones. The probability of the target tone was varied across conditions at 10%, 30%, or 50% to assess possible developmental changes in P300 amplitude. Memory capacity was assessed with forward and reverse digit spans. Circumference of the head also was measured. P300 latency decreased with age, and P300 amplitude tended to become larger with age. Polynomial regression analyses revealed significant quadratic trends in these relationships, with changes leveling off for older subjects. Digit span and head circumference also were related curvilinearly to P300 values. Multiple regression analysis indicated that changes in age and memory span both predicted significant changes in P300 latency and amplitude. Target stimulus probability generally affected all subjects in a similar fashion, although the strength of the correlational relationships tended to decline with increases in probability. Developmental changes for the N1, P2, and N2 components from the standard stimuli also were obtained. The results are discussed in terms of previous P3 findings for children and their implications for future studies.     

Short-term memory in children with sickle cell disease: Executive versus modality-specific processing deficits

Prior research has identified a number of areas of cognitive deficit among children with sickle cell disease (SCD), including decrements in memory span and working memory. The present study examined short-term memory span and working memory performance among children with SCD (n = 25) and demographically matched comparison children (n = 25) using digit span, spatial span, and the self-ordered pointing test. Children with SCD showed difficulties only for digit span-backward. Additional cognitive ability measures administered indicated auditory processing was an area of deficit related to digit span-backward performance. The study suggests that modality specific deficits are one factor in short-term memory span for children with SCD. The cause of this deficit is unclear, but may involve both central and peripheral components of auditory processing.     

White matter microstructure of the cingulum and cerebellar peduncle is related to sustained attention and working memory: A diffusion tensor imaging study

The non-invasive imaging technique of diffusion tensor imaging (DTI) has been used to investigate the microstructural properties of white matter (WM). The present study investigated whether individual differences in the WM structure of normal subjects as measured by fractional anisotropy (FA) values correlate with cognitive performance in terms of sustained attention and working memory. Subjects underwent DTI and performed the Continuous Performance Test (CPT) and N-back task. FA values throughout the brain were correlated with behavioral performance on a voxel-by-voxel basis to investigate relationships between WM microstructure and cognitive function. The discriminability index of CPT correlated positively with FA of the right cingulum. Accuracy of the 2-back task correlated positively with FA in bilateral cerebellar peduncles. WM microstructure of the right cingulum and bilateral cerebellar peduncles appears related to cognitive function such as sustained attention and working memory in the human brain.     

Theta and alpha oscillations during working-memory maintenance predict successful long-term memory encoding

To date, much is known about the neural mechanisms underlying working-memory (WM) maintenance and long-term-memory (LTM) encoding. However, these topics have typically been examined in isolation, and little is known about how these processes might interact. Here, we investigated whether EEG oscillations arising specifically during the delay of a delayed matching-to-sample task reflect successful LTM encoding. Given previous findings of increased alpha and theta power with increasing WM load, together with the assumption that successful memory encoding involves processes that are similar to those that are invoked by increasing WM load, alpha and theta power should be higher for subsequently remembered stimuli. Consistent with this assumption, we found stronger alpha power for subsequently remembered stimuli over occipital-to-parietal scalp sites. Furthermore, stronger theta power was found for subsequently remembered stimuli over parietal-to-central electrodes. These results support the idea that alpha and theta oscillations modulate successful LTM encoding.