Digit Span Recall Research Articles

Identifying Links Between Latent Memory and Speech Recognition Factors.

The link between memory ability and speech recognition accuracy is often examined by correlating summary measures of performance across various tasks, but interpretation of such correlations critically depends on assumptions about how these measures map onto underlying factors of interest. The present work presents an alternative approach, wherein latent factor models are fit to trial-level data from multiple tasks to directly test hypotheses about the underlying structure of memory and the extent to which latent memory factors are associated with individual differences in speech recognition accuracy. Latent factor models with different numbers of factors were fit to the data and compared to one another to select the structures which best explained vocoded sentence recognition in a two-talker masker across a range of target-to-masker ratios, performance on three memory tasks, and the link between sentence recognition and memory. Young adults with normal hearing (N = 52 for the memory tasks, of which 21 participants also completed the sentence recognition task) completed three memory tasks and one sentence recognition task: reading span, auditory digit span, visual free recall of words, and recognition of 16-channel vocoded Perceptually Robust English Sentence Test Open-set sentences in the presence of a two-talker masker at target-to-masker ratios between +10 and 0 dB. Correlations between summary measures of memory task performance and sentence recognition accuracy were calculated for comparison to prior work, and latent factor models were fit to trial-level data and compared against one another to identify the number of latent factors which best explains the data. Models with one or two latent factors were fit to the sentence recognition data and models with one, two, or three latent factors were fit to the memory task data. Based on findings with these models, full models that linked one speech factor to one, two, or three memory factors were fit to the full data set. Models were compared via Expected Log pointwise Predictive Density and post hoc inspection of model parameters. Summary measures were positively correlated across memory tasks and sentence recognition. Latent factor models revealed that sentence recognition accuracy was best explained by a single factor that varied across participants. Memory task performance was best explained by two latent factors, of which one was generally associated with performance on all three tasks and the other was specific to digit span recall accuracy at lists of six digits or more. When these models were combined, the general memory factor was closely related to the sentence recognition factor, whereas the factor specific to digit span had no apparent association with sentence recognition. Comparison of latent factor models enables testing hypotheses about the underlying structure linking cognition and speech recognition. This approach showed that multiple memory tasks assess a common latent factor that is related to individual differences in sentence recognition, although performance on some tasks was associated with multiple factors. Thus, while these tasks provide some convergent assessment of common latent factors, caution is needed when interpreting what they tell us about speech recognition.

Frequency and Risk Factors of Acute Kidney Injury During Diabetic Ketoacidosis in Children and Association With Neurocognitive Outcomes

Acute kidney injury (AKI) occurs commonly during diabetic ketoacidosis (DKA) in children, but the underlying mechanisms and associations are unclear. To investigate risk factors for AKI and its association with neurocognitive outcomes in pediatric DKA. This cohort study was a secondary analysis of data from the Pediatric Emergency Care Applied Research Network Fluid Therapies Under Investigation in DKA Study, a prospective, multicenter, randomized clinical trial comparing fluid protocols for pediatric DKA in 13 US hospitals. Included DKA episodes occurred among children age younger than 18 years with blood glucose 300 mg/dL or greater and venous pH less than 7.25 or serum bicarbonate level less than 15 mEq/L. DKA requiring intravenous insulin therapy. AKI occurrence and stage were assessed using serum creatinine measurements using Kidney Disease: Improving Global Outcomes criteria. DKA episodes with and without AKI were compared using univariable and multivariable methods, exploring associated factors. Among 1359 DKA episodes (mean [SD] patient age, 11.6 [4.1] years; 727 [53.5%] girls; 651 patients [47.9%] with new-onset diabetes), AKI occurred in 584 episodes (43%; 95% CI, 40%-46%). A total of 252 AKI events (43%; 95% CI, 39%-47%) were stage 2 or 3. Multivariable analyses identified older age (adjusted odds ratio [AOR] per 1 year, 1.05; 95% CI, 1.00-1.09; P = .03), higher initial serum urea nitrogen (AOR per 1 mg/dL increase, 1.14; 95% CI, 1.11-1.18; P < .001), higher heart rate (AOR for 1-SD increase in z-score, 1.20; 95% CI, 1.09-1.32; P < .001), higher glucose-corrected sodium (AOR per 1 mEq/L increase, 1.03; 95% CI, 1.00-1.06; P = .001) and glucose concentrations (AOR per 100 mg/dL increase, 1.19; 95% CI, 1.07-1.32; P = .001), and lower pH (AOR per 0.1 increase, 0.63; 95% CI, 0.51-0.78; P < .001) as variables associated with AKI. Children with AKI, compared with those without, had lower scores on tests of short-term memory during DKA (mean [SD] digit span recall: 6.8 [2.4] vs 7.6 [2.2]; P = .02) and lower mean (SD) IQ scores 3 to 6 months after recovery from DKA (100.0 [12.2] vs 103.5 [13.2]; P = .005). Differences persisted after adjusting for DKA severity and demographic factors, including socioeconomic status. These findings suggest that AKI may occur more frequently in children with greater acidosis and circulatory volume depletion during DKA and may be part of a pattern of multiple organ injury involving the kidneys and brain.

Dopaminergic gene methylation is associated with cognitive performance in a childhood monozygotic twin study

ABSTRACTIndividual differences in cognitive function are due to a combination of heritable and non-heritable factors. A large body of evidence from clinical, cognitive, and pharmacological neuroscience implicates dopaminergic gene variants as modulators of cognitive functions. Neuroepigenetic studies demonstrate environmental factors also influence complex phenotypes by affecting gene expression regulation. To evaluate the mechanism of environmental influence on cognitive abilities, we examined if epigenetic regulation of dopaminergic genes plays a role in cognition. Using a DNA methylation profiling microarray, we used a monozygotic (MZ) twin difference design to evaluate if co-twin differences in methylation of CpG sites near six dopaminergic genes predicted differences in response inhibition and memory performance. Studying MZ twins allows us to assess if environmentally driven differences in methylation affect differences in phenotype while controlling for the influence of genotype and shared family environment. Response inhibition was assessed with the flanker task and short-term and working memory were assessed with digit span recall. We found MZ co-twin differences in DRD4 gene methylation predicted differences in short-term memory. MZ differences in COMT, DBH, DAT1, DRD1, and DRD2 gene methylation predicted differences in response inhibition. Taken together, findings suggest methylation status of dopaminergic genes may influence cognitive functions in a dissociable manner. Our results highlight the importance of the epigenome and environment, over and above the influence of genotype, in supporting complex cognitive functions.

Saccade frequency response to visual cues during gait in Parkinson's disease: the selective role of attention.

Gait impairment is a core feature of Parkinson's disease (PD) with implications for falls risk. Visual cues improve gait in PD, but the underlying mechanisms are unclear. Evidence suggests that attention and vision play an important role; however, the relative contribution from each is unclear. Measurement of visual exploration (specifically saccade frequency) during gait allows for real-time measurement of attention and vision. Understanding how visual cues influence visual exploration may allow inferences of the underlying mechanisms to response which could help to develop effective therapeutics. This study aimed to examine saccade frequency during gait in response to a visual cue in PD and older adults and investigate the roles of attention and vision in visual cue response in PD. A mobile eye-tracker measured saccade frequency during gait in 55 people with PD and 32 age-matched controls. Participants walked in a straight line with and without a visual cue (50cm transverse lines) presented under single task and dual-task (concurrent digit span recall). Saccade frequency was reduced when walking in PD compared to controls; however, visual cues ameliorated saccadic deficit. Visual cues significantly increased saccade frequency in both PD and controls under both single task and dual-task. Attention rather than visual function was central to saccade frequency and gait response to visual cues in PD. In conclusion, this study highlights the impact of visual cues on visual exploration when walking and the important role of attention in PD. Understanding these complex features will help inform intervention development.

Pupillary Responses as a Biomarker ofEarly Risk for Alzheimer's Disease.

Task-evoked pupillary responses may be a psychophysiological biomarker of early risk for mild cognitive impairment (MCI) and Alzheimer's disease (AD). Pupil dilation during cognitive tasks reflects cognitive effort until compensatory capacity is surpassed and performance declines are manifest, and reflects activation in the locus coeruleus, where degenerative changes have been found in the earliest stages of AD. We recorded pupillary responses during digit span recall in 918 participants ages 56-66. Despite normal performance, amnestic single-domain MCI (S-MCI) participants showed greater pupil dilation than non-amnestic S-MCI and cognitively normal (CN) participants at lower cognitive loads. Multi-domain MCI (M-MCI) participants failed to modulate effort across cognitive loads and showed poorer performance. Pupillary responses differentiated MCI and CN groups. Amnestic S-MCI participants required compensatory effort to maintain performance, consistent with increased risk for decline. Greater effort in CN individuals might indicate risk for MCI. Results are consistent with dysfunction in locus coeruleus-linked brain systems. This brief task shows promise as a biomarker for early MCI and AD risk prediction.

The Workload Curve: Subjective Mental Workload.

In this paper I begin looking for evidence of a subjective workload curve. Results from subjective mental workload assessments are often interpreted linearly. However, I hypothesized that ratings of subjective mental workload increase nonlinearly with unitary increases in working memory load. Two studies were conducted. In the first, the participant provided ratings of the mental difficulty of a series of digit span recall tasks. In the second study, participants provided ratings of mental difficulty associated with recall of visual patterns. The results of the second study were then examined using a mathematical model of working memory. An S curve, predicted a priori, was found in the results of both the digit span and visual pattern studies. A mathematical model showed a tight fit between workload ratings and levels of working memory activation. This effort provides good initial evidence for the existence of a workload curve. The results support further study in applied settings and other facets of workload (e.g., temporal workload). Measures of subjective workload are used across a wide variety of domains and applications. These results bear on their interpretation, particularly as they relate to workload thresholds.

The nature of dual-task interference during gait in incident Parkinson’s disease

Dual-task interference during gait is a common phenomenon in older adults and people with Parkinson’s disease (PD). Dual-task performance is driven by cognitive processes involving executive function, attention and working memory which underpin resource capacity and allocation. The underlying processes that contribute to dual-task interference are poorly understood, and confounded by methodological differences. The aim of this study was to explore the nature of dual-task interference in PD with respect to age-matched controls. We examined 121 people with early PD and 189 controls and controlled for baseline task demand on both tasks allowing between-group differences to be attributed to dual-task interference rather than differences in baseline performance. We also compared a wide range of gait characteristics to evaluate the pattern of interference. Participants walked for two minutes at a preferred pace under single- and dual-task (test of working memory capacity−digit span recall) conditions. In a subgroup task demand was increased (digit span+1) (n=55 control, n=44 PD) to assess the influence of resource capacity. Finally the association between dual-task interference with motor and cognitive characteristics was examined to evaluate resource capacity and allocation. PD and controls responded similarly to the dual-task for all gait characteristics except for step width and step width variability and this was the same when task demand increased (dual+1). Control participants took wider steps (p=0.006) and step width variability increased significantly for controls (p=0.001) but not PD. Interference was specific to the gait characteristic rather than a global pattern of impairment. Digit span error rates were not significantly different between groups during dual-task performance. There were no significant correlations with dual-task interference and global cognition, motor deficit, and executive function for either group. Effects of dual-tasks on gait performance are twofold and specific to the gait characteristic. They reflect an age-related reduction in gait performance (especially forward progression) in PD and controls possibly due to reduced resource capacity; and secondly, show postural stability during walking in early PD is disproportionately affected highlighting a PD-specific dual-task co-ordination deficit. Further work is required to identify the cognitive, executive and motor correlates of dual-task interference from which inferences about underlying cognitive processes can be made. These findings inform an understanding of dual-task impairment in early PD and suggest that management should target postural control under dual-task conditions from the early stages.

The Signs of a Savant: Language against the Odds (review)

The Signs of a Savant: Language against the Odds, by Neil Smith, IanthiTsimpli, Gary Morgan, and Bencie Woll (Cambridge: Cambridge University Press, 2011, 219 pp., ISBN 978-0-52185-227-2)THIS BOOK PRESENTS a case study of a middle-aged man named Christopher, an autistic savant who demonstrates an incredible ability to master multiple languages despite a below-average general IQ.The crux of this new book centers on a crucial question: How will an autistic man with a gift for languages and severe apraxia perform when taught signed language? As the study unfolds, we gain valuable insight into the modularity of the mind, particularly the cognitive and linguistic structures, which are intertwined.Based on nearly twenty years of empirical observations and psychometric tests of the subject's abilities, the first chapter introduces us to Christopher, whose early diagnosis revealed developmental difficulties that would produce delays in speech fluency and motor coordination. Christopher exhibited an extremely low nonverbal performance, with artistic IQ ability in the 40-60 range. However, his linguistic IQ in English - 120 - stands in stark contrast. Moreover, his severe apraxia results in poor performance in the copying of nonrepresentational gestures. Although he was able to recognize conventional gestures (e.g., brushing teeth), he was not able to make the appropriate movements when prompted. Such severe motor limitations in the face of his savant linguistic abilities have led the authors to investigate how Christopher will perform when given an opportunity to learn British Sign Language (BSL). After laying out important theoretical assumptions based on Chomskyan linguistics, modularity, and Baddeley's memory model, the chapter ends with well-specified predictions about how Christopher will perform in BSL. The authors predicted that Christopher's limited cognitive ability to tie iconic signs to their referents would hamper his acquisition of lexical signs. He was also expected to perform better on the comprehension of lexical signs and grammatical devices than with facial expressions and sign production due to his inability to maintain eye contact with the signer, his apraxia, and his linguistic savant abilities.The second chapter provides a comprehensive overview of the linguistic structure of BSL, covering the gamut of phonological, morphosyntactic, and facial elements of signed languages, as well as giving examples of signs that might be problematic for someone who avoids social eye contact (e.g., boss and god are distinguished only by direction of eyegaze) . The chapter tackles most of the critical literature on sign modality, iconicity sign language acquisition, and sign topography. Aside from a few references to Christopher's performance in digit-span recall using signed stimuli, the entire chapter appears to stand independently of the study of Christopher's foray into signed language learning.The third chapter, the methods section, details the training and data-collection phase of Christopher's signed language learning experience. Two hours a month of sign language learning for twelve months may not be an adequate training period for most learners, but it was more than twice the amount of time Christopher needed to master his other spoken languages. His training included morphosyntactic structures of signed languages such as topic markers, aspect morphology, nonmanual markers, verb locative agreement, and narratives involving multiple characters. Then he was tested at five different intervals for his comprehension and production of lexical signs and manual grammatical devices, as well as his performance on facial markers. To compare Christopher's BSL learning to normal second language learning of BSL, forty hearing volunteers were recruited to learn BSL using the same curriculum as Christopher's, albeit in onehour sessions over a twelve-week period.Chapter 4 evaluates Christopher's lexical and syntactic development and that of the comparison group. …

Neurocognitive Deficits Associated With the Hepatitis C Virus Among Incarcerated Men

The purpose of this preliminary study was to examine cognitive functioning in inmates with the hepatitis C virus (HCV) and to investigate relationships among performance on the Repeatable Battery for the Assessment of Neuropsychological Status-Form A (RBANS; Randolph, 1998). Data from 43 HCV+ inmates were reviewed retrospectively and compared with a sample of HCV– inmates. Significant differences were found on two of five indices (Attention: U = 537.5, p = .003; r = –.32; Total: U = 643.0, p = .048; r = –.22) and four subtests: Coding (U = 326.0, p <.001, r = –.53), Digit Span (U = 634.0, p = .038, r = –.22), Story Memory (U = 625.5, p = .032, r = –.24), and Story Recall (U = 548.5, p = .004, r = –.31), with the HCV group scoring lower on all significant measures. In this study the RBANS proved to be an efficient measure with clinical utility among an HCV population. Within this incarcerated population patterns of performance were “typical” of current literature, with impaired attention appearing earlier in the disease process, and the study invites further exploration into proposed cognitive deficits among this population where HCV is highly prevalent.

Computerized analysis of error patterns in digit span recall

We analyzed error patterns during digit span (DS) testing in four experiments. In Experiment 1, error patterns analyzed from a community sample of 427 subjects revealed strong primacy and recency effects. Subjects with shorter DSs showed an increased incidence of transposition errors in comparison with other error types and a greater incidence of multiple errors on incorrect trials. Experiment 2 investigated 46 young subjects in three test sessions. The results replicated those of Experiment 1 and demonstrated that error patterns of individual subjects were consistent across repeated test administrations. Experiment 3 investigated 40 subjects from Experiment 2 who feigned symptoms of traumatic brain injury (TBI) with 80% of malingering subjects producing digit spans in the abnormal range. A digit span malingering index (DSMI) was developed to detect atypical error patterns in malingering subjects. Overall, 59% of malingering subjects with abnormal digit spans showed DSMIs in the abnormal range and DSMI values correlated significantly with the magnitude of malingering. Experiment 4 compared 29 patients with TBI with a new group of 38 control subjects. The TBI group showed significant reductions in digit span. Overall, 32% of the TBI patients showed DS abnormalities and 11% showed abnormal DSMIs. Computerized error-pattern analysis improves the sensitivity of DS assessment and can assist in the detection of malingering.

Pupillary Dilation as an Index of Task Demands

To analyze how pupillary responses reflect mental effort and allocation of processing resources under several load conditions, the pupil diameter of 18 participants was recorded during an auditory digit-span recall task under three load conditions: Low (5 digits), Moderate (8 digits), and Overload (11 digits). In previous research, under all load conditions a significant linear enlargement in pupil diameter was observed as each digit was presented. Significant dilations from the end of the presentation phase to the beginning of the recall phase were also observed but only under low and moderate loads. Contrary to previous research, under the Overload condition, no reduction in pupil diameter was observed when resource limits were exceeded; however, a plateau was observed when the ninth digit was presented until the beginning of the recall phase. Overall, pupillometric data seem to indicate that participants may keep processing actively even though resources are exceeded.

Executive control of working memory in schizophrenia

There is considerable evidence that working memory impairment is a common feature of schizophrenia. The present study assessed working memory and executive function in 54 participants with schizophrenia, and a group of 54 normal controls matched to the patients on age, gender and estimated premorbid IQ, using traditional and newer measures of executive function and two dual tasks—Telephone Search with Counting and the Memory Span and Tracking Task. Results indicated that participants with schizophrenia were significantly impaired on all standardised measures of executive function with the exception of a composite measure of the Trail Making Test. Results for the dual task measures demonstrated that while the participants with schizophrenia were unimpaired on immediate digit span recall over a 2-min period, they recalled fewer digit strings and performed more poorly on a tracking task (box-crossing task) compared with controls. In addition, participants with schizophrenia performed more poorly on the tracking task when they were required to simultaneously recall digits strings than when they performed this task alone. Contrary to expectation, results of the telephone search task under dual conditions were not significantly different between groups. These results may reflect the insufficient complexity of the tone-counting task as an interference task. Overall, the present study showed that participants with schizophrenia appear to have a restricted impairment of their working memory system that is evident in tasks in which the visuospatial sketchpad slave system requires central executive control.

Digit span recall error analysis in pediatric cochlear implant users

The errors made by 37 pediatric cochlear implant users and age-matched normal-hearing children during forward and backward digit span recall were analyzed. All children were between 8 and 10 years old. The children who used implants had at least 4.5 years of experience with their device. Error classification was made using four categories: item, order, omission, or combination errors. Recall of digits not presented on a given trial was classified as item errors. The recall of all correct digits in an incorrect order was considered to be an order error. Results from a univariate ANOVA revealed main effects for error type, recall condition, and hearing ability. In addition, the error type by recall condition interaction revealed that order errors increased more in backward digit span recall than any other type of error for both normal-hearing children and children with cochlear implants. The present results are consistent with previous studies, suggesting that the shorter digit spans of children using cochlear implants are not primarily related to perceptual difficulties but appear to reflect memory processing problems related to slower subvocal verbal rehearsal and serial scanning of items in short-term memory.

Speech timing and working memory in profoundly deaf children after cochlear implantation

Thirty-seven profoundly deaf children between 8- and 9-years-old with cochlear implants and a comparison group of normal-hearing children were studied to measure speaking rates, digit spans, and speech timing during digit span recall. The deaf children displayed longer sentence durations and pauses during recall and shorter digit spans compared to the normal-hearing children. Articulation rates, measured from sentence durations, were strongly correlated with immediate memory span in both normal-hearing and deaf children, indicating that both slower subvocal rehearsal and scanning processes may be factors that contribute to the deaf children’s shorter digit spans. These findings demonstrate that subvocal verbal rehearsal speed and memory scanning processes are not only dependent on chronological age as suggested in earlier research by Cowan and colleagues (1998). Instead, in this clinical population the absence of early auditory experience and phonological processing activities before implantation appears to produce measurable effects on the working memory processes that rely on verbal rehearsal and serial scanning of phonological information in short-term memory.

Exploratory-motor task to evaluate right frontal lobe damage

An exploratory-motor (E-M) task was performed by 20 patients with right hemispheric damage and unilateral spatial neglect and by 15 adult controls. None of the subjects in the control group demonstrated E-M neglect, other types of unilateral spatial neglect, or motor impersistence. In the unilateral spatial neglect group, 14 of 20 patients revealed E-M neglect. The presence or absence of E-M neglect related to word fluency, digit span recall (backward), and motor impersistence. In addition, E-M neglect frequency was observed in patients with lesions in the frontal lobe. The frontal lobe may play an important role in the performance of an E-M task. Therefore, we think that E-M task performance is a useful method for evaluating the site of right frontal lobe damage.

Working Memory: Activation Limitations on Retrieval

Two experiments which require subjects to hold a digit span while solving an equation and then recall the digit span are performed. The size of the memory span and the complexity of the equation are manipulated as well as whether the subject is required to substitute items from the digit span for constants in the equation. As either task (digit span recall or equation solving) gets more complex there are performance decrements (accuracy or latency) not only in that task but also in the other task. It is also shown that the majority of the errors are misretrievals. These results are consistent with the proposal that working memory load has its impact on retrieval from memory. These results are fit by the ACT-R theory (Anderson, 1993) which assumes that there is a limit on source activation and that this activation has to be divided between the two tasks. As either task increases in complexity there is less activation for retrieval of information from declarative memory. Subjects’ misretrievals of associatively related information could be predicted by assuming a partial matching process in ACT-R.

Effects of food snacks on cognitive performance in male college students

The effects of food snacks consumed in the late afternoon on cognitive performance in college-aged men were investigated in two experiments. The effects of the snacks were tested in the same subjects after they either consumed or skipped lunch. In the first experiment, the calorie-rich snack was a confectionery product, while in the second experiment, the snack was fruit-flavored yogurt. In both experiments, performance on cognitive tasks following consumption of the calorie-rich snack was compared to performance following consumption of a very low calorie snack (lemon-lime flavored diet soda without caffeine). Four cognitive tasks were employed: digit span recall (forward and backward), arithmetic reasoning, reading, and attention. In both experiments, subjects recalled significantly more digits in the backward digit span test and responded significantly faster in the attention task when they had consumed the calorific snack than when they had consumed the diet soft drink. Additionally, in Experiment 2, subjects solved significantly more arithmetic problems and solved these problems in significantly less time after eating a fruit-flavored yogurt than after consuming the diet soft drink. Results of these experiments suggest that a late afternoon energy-containing snack can have positive effects on cognitive performance on tasks that require sustained attention.

Effects of a transformational mnemonic strategy to facilitate digit span recall by mildly handicapped students.

24 mildly handicapped students were taught two 9-digit numbers in a cross-over design in which number of digits and order of presentation of condition were counterbalanced. In the cluster-rehearsal condition, students were taught the digit series in clusters of three with overt experimenter-led rehearsal. In the mnemonic condition, numbers were transformed into isomorphic pictorial representations of concrete objects and pictured as appearing on the head, hand, and foot of a man, woman, and child, respectively, in each of three pictures. Free and cued recall scores were collected on immediate and three delayed recall intervals, and scored for position, sequence, and span scores. Recall data were obscured by ceiling effects but consistently favored mnemonic instruction. Cued recall scores collapsed across recall intervals statistically favored mnemonic instruction according to nonparametric tests. In addition, as in previous investigations of mnemonic instructions, response latencies were significantly greater under mnemonic instruction. Finally, collapsed item-position scores showed bowed serial-position curves in cluster-rehearsal but not mnemonic conditions. Implications for further research are given.

Development of phonetic memory in disabled and normal readers

The development of phonetic codes in memory of 141 pairs of normal and disabled readers from 7.8 to 16.8 years of age was tested with a task adapted from L. S. Mark, D. Shankweiler, I. Y. Liberman, and C. A. Fowler ( Memory & Cognition, 1977 , 5, 623–629) that measured false-positive errors in recognition memory for foil words which rhymed with words in the memory list versus foil words that did not rhyme. Our younger subjects replicated Mark et al., showing a larger difference between rhyming and nonrhyming false-positive errors for the normal readers. The older disabled readers' phonetic effect was comparable to that of the younger normal readers, suggesting a developmental lag in their use of phonetic coding in memory. Surprisingly, the normal readers' phonetic effect declined with age in the recognition task, but they maintained a significant advantage across age in the auditory WISC-R digit span recall test, and a test of phonological nonword decoding. The normals' decline with age in rhyming confusion may be due to an increase in the precision of their phonetic codes.

Clinical evaluation of dementia in Down's syndrome: a preliminary report.

Down's syndrome residents were found to have significantly greater impairment on measures of orientation, attention span, digit span recall, visual memory, object identification and praxis, and were more likely to have pathological released reflexes than age and IQ matched controls. Neuropsychiatric status tended to worsen with advancing age in Down's syndrome, but not in controls. Forty-five percent of DS individuals age 45 or older had a full syndrome of dementia, compared to only 5% of controls. Although further research is necessary, particularly employing larger samples and more detailed medical screening, these results support the association of dementia Alzheimer type with Down's syndrome.