Biomedical subjects

P Kittler

Publications and source records attributed to P Kittler.

4 recordsLinked to original sources

PubMed2006

Verbal intrusions precede memory decline in adults with Down syndrome.

BACKGROUND: Verbal intrusion errors are irrelevant responses made in the course of verbal memory retrieval or language production that have been associated with disruption of executive functions and the prefrontal cortex. They have been observed to occur more frequently both with normal aging and with neurodegenerative diseases such as Alzheimer's disease (AD). The purpose of this study was to longitudinally examine the production of verbal intrusions among middle-aged adults with Down syndrome (DS) and unspecified intellectual disability (ID) to determine whether producing verbal intrusions at one point in time was related to subsequent verbal memory performance. Because of the combination of a relative deficit in verbal working memory (WM), premature aging, and higher risk of AD among adults with DS, it was predicted that they would make more verbal intrusions than adults with unspecified ID. METHODS: Word List recall (WLR), the Selective Reminding Test (SRT), and the Cued Recall Test (CRT), were administered three times at 18-month intervals during a 3-year period. In Analysis 1, aetiology differences in making intrusion errors were examined. Twenty-three adults with unspecified ID in the moderate to mild range [time 1(T1) mean age = 47.2 years] and 42 adults with DS (T1 mean age = 44.3) participated. WLR is a serial WM task beginning at two word sequences and progressively increasing by one word every three trials. WLR intrusions were analysed because they were least likely to include 'educated guesses' because this test is not based on semantic categories. In Analysis 2, we only examined participants with DS. They were divided into two groups, 16 individuals who made at least one intrusion error at T1 (T1 mean age = 45.8) and 26 who did not (T1 mean age = 43.3). Longitudinal performance for these groups was analysed to determine whether the group that intruded at T1 did more poorly on subsequent memory tests. RESULTS: A higher proportion of responses comprised intrusions for the group with DS and a higher percentage of the participants with DS made at least one intrusion error when compared with participants with unspecified ID (74% and 44% respectively). Those participants with DS who made at least one intrusion error at T1 showed a subsequent decline in performance on both WLR and the SRT. CONCLUSIONS: The production of intrusion errors during a verbal WM task is a characteristic of middle-aged adults with DS. This suggests compromised executive function and control of inhibition within the verbal modality for this group. Further, verbal intrusions are a qualitative aspect of verbal processing that merit attention in considering the issue of deficiencies of language and verbal WM abilities among people with DS. Last, and perhaps most importantly, although not definitive diagnostically, an increase in verbal intrusions is a potentially noteworthy signal when evaluating the cognitive health of adults with DS.

Adult↗

PubMed2004

Sex differences in performance over 7 years on the Wechsler Intelligence Scale for Children--Revised among adults with intellectual disability.

BACKGROUND: The aim of this study was to explore changes related to sex differences on the Wechsler Intelligence Scale for Children - Revised (WISC-R) subtest performance over a 7-year interval in middle-aged adults with intellectual disability (ID). Cognitive sex differences have been extensively studied in the general population, but there are few reports concerning individuals with ID. Sex differences are of current relevance to actively debated issues such as cognitive changes during menopause and risk for Alzheimer's disease. Given that hormonal effects on cognition have been observed in the general population, particularly in areas such as visuospatial processing, and individuals with Down's syndrome (DS) have been reported to be hormonally and reproductively atypical, we analysed our data to allow for the possibility of an aetiology-specific profile of sex differences for these adults. METHODS: The WISC-R subtests were administered in a longitudinal study, as part of a more comprehensive test battery, at least twice within 7 years. Participants were 18 females with ID without DS [age at first test time (time 1): mean = 40.5; IQ: mean = 59.3], 10 males with ID without DS (age at time 1: mean = 42.4; IQ: mean = 59.4), 21 females with DS (age at time 1: mean = 37.9; IQ: mean = 51.6), and 21 males with DS (age at time 1: mean = 40.3; IQ: mean = 54.3). All participants were in the mild to moderate range of ID and were displaying no changes suggestive of early dementia. RESULTS: Females, regardless of aetiology of ID, exhibited a robust superiority on the coding subtest, which parallels the widely reported difference among adults in the general population. Additionally, there was a decline in overall performance during the 7-year study interval, particularly on the verbal subscale subtests, but there was no evidence of sex-differentiated decline. There were also marginal sex by aetiology interactions on the object assembly and block design subtests, suggesting that males with unspecified ID might perform better than their female peers, but among adults with DS, females might do better than males. CONCLUSIONS: This study supports the presence of cognitive sex differences in the population with ID as indicated by female superiority on the WISC-R coding subtest. Extending this observation to adults with ID has implications for explanations of female advantage on this task, which now have to account for its presence among individuals with a broader range of intellectual capabilities, more atypical developmental histories and more varied genotypes than previously considered. Trends towards sex by aetiology interactions on the two visuoconstructive subtests, while marginal, were sufficient to warrant continued consideration of the idea of a distinct profile of sex differences for adults with DS and to justify looking at the effects of sex separately within different aetiologies of ID.

Adult↗

PubMed2002

Cued recall in early-stage dementia in adults with Down's syndrome.

BACKGROUND: Memory declines were evaluated with an adaptation of the Cued Recall Test (CRT) in 19 adults with Down's syndrome (DS) with mild or moderate intellectual disability (ID) who were at an early-stage of dementia of the Alzheimer type (DAT), and their performance was compared to peer groups of 75 adults with DS and 66 adults with ID without DS who were not suspected of functional declines. METHOD: The CRT consisted of a training period in which 12 items were presented, four at a time, with each item accompanied by a unique category cue. The testing phase consisted of three trials which generated two measures, a free recall score (FRS; spontaneous recall of the list of 12 items) and a total score (TS; FRS plus items recalled when the category cue was provided). RESULTS: It was found that a cut-off value of < or = 23 on the TS resulted in a sensitivity of 94.7% and a specificity of 93.9% with a positive predictive value of 81.9% when those individuals with DAT were compared to the participants with ID without DS. Eight of these individuals with DAT had relatively poor performance on the CRT compared to their healthy peers at a baseline when they were not suspected of functional declines, suggesting that memory declines can occur several years prior to the identification of DAT. In addition, 17 participants with DS without a diagnosis of DAT met the criterion for the cut-off score. Longitudinal data and converging measures indicated that there was the possibility that 15 of these individuals are in a 'pre-clinical' stage of decline. CONCLUSION: The usefulness of the CRT as a screening test for early memory deficits for this population needs to be confirmed by following these participants for an extended period of time and by studying an independent sample.

Aged↗

PubMed1989

Shifts in hemispheric advantage during familiarization with complex visual patterns.

Twenty females unfamiliar with kanji were given a recognition task involving tachistoscopic presentation of kanji to the right and left visual fields. Repeated exposure to these novel stimuli resulted in significantly increased competence at the task. To analyze different approaches to the task, subjects were divided into an initial left visual field advantage and an initial right visual field advantage group. Over the course of the experiment subjects in the initial left visual field advantage group shifted from a left to a right visual field advantage, showing both a linear trend and a quadratic trend, while the initial right visual field advantage group showed only a quadratic trend. The results are consistent with observations in other novel stimuli situations which have demonstrated a shift in hemispheric advantage from right to left with increased competence and which have demonstrated individual differences in the pattern of shifting hemispheric advantage.

Adult↗