Catherine Ludwig

Adult age differences in the Color Stroop Test: A comparison between an Item-by-item and a Blocked version

The Color Stroop Test is consensually considered as a task to assess the efficiency of inhibitory mechanisms. If the Stroop interference effect is largely undisputed, it is also acknowledged that the size of this effect varies as a function of various task manipulations, such as the task format. The aim of the present study was to compare the size of adult age-related differences in inhibition as assessed by two different versions of the Color Stroop Test: a standard Blocked paper-and-pencil version and a computerized Item-by-item one. Results showed pronounced age-related differences in the interference effect in the Blocked version, but not in the Item-by-item one. These findings are discussed in terms of the characteristics of the tasks. The choice of the appropriate version with respect to clinical aims is also addressed.

Age differences and divided attention: is there a general deficit?

It was the goal of this study to determine whether there were age differences specifically associated with the ability to simultaneously execute two tasks, and whether cognitive costs correlated across different situations. Eighty-one young and 86 older adults underwent nine tasks, administered both in single and in dual conditions. Results showed large age differences in raw performances in all conditions. However, a larger cognitive cost in the older adults sample, as assessed by an Age 2 Condition interaction, was observed only for four out of the nine tasks. Furthermore, age effects were greatly diminished once performance in the single tasks was controlled for. Correlations between the dual tasks, or between the cognitive cost scores, were very low once age was partialled out. Results do not support the notion of general coordination costs and speak against a generalized increase in divided attention costs with advancing age.

Individual differences in cognitive plasticity: an investigation of training curves in younger and older adults

To date, cognitive intervention research has provided mixed but nevertheless promising evidence with respect to the effects of cognitive training on untrained tasks (transfer). However, the mechanisms behind learning, training effects and their predictors are not fully understood. Moreover, individual differences, which may constitute an important factor impacting training outcome, are usually neglected. We suggest investigating individual training performance across training sessions in order to gain finer-grained knowledge of training gains, on the one hand, and assessing the potential impact of predictors such as age and fluid intelligence on learning rate, on the other hand. To this aim, we propose to model individual learning curves to examine the intra-individual change in training as well as inter-individual differences in intra-individual change. We recommend introducing a latent growth curve model (LGCM) analysis, a method frequently applied to learning data but rarely used in cognitive training research. Such advanced analyses of the training phase allow identifying factors to be respected when designing effective tailor-made training interventions. To illustrate the proposed approach, a LGCM analysis using data of a 10-day working memory training study in younger and older adults is reported.

Brain energy metabolism in Alzheimer’s disease: 99mTc-HMPAO SPECT imaging during verbal fluency and role of astrocytes in the cellular mechanism of 99mTc-HMPAO retention ☆

The central hypothesis of the study which has been carried out as part of the NRP38 program, is that perturbations of brain energy metabolism are critically involved in the neurodegeneration occurring in Alzheimers disease (AD) and that they may correlate with early cognitive dysfunctioning. In the present multidisciplinary study we set out to monitor brain energy metabolism using FDG-PET and HMPAO-SPECT imaging in a cohort of individuals over 65 years of age, drawn from the general population. HMPAO-SPECT imaging, which is a simpler and more widely accessible imaging procedure than FDG-PET, was performed under basal conditions and during the performance of a cognitive task (verbal fluency test). Three groups were studied. Two groups (groups I and II) included individuals age 65 or more, with no cognitive impairment and carrying an APOE4 positive or APOE4 negative phenotype, respectively; a third group (group III) included patients with clinical signs of AD. Each subject entering the study underwent an FDG-PET, an HMPAO-SPECT and an extensive battery of neuropsychological tests which assess various aspects of cognitive functioning, with a strong emphasis on working memory, divided attention and executive functions. A total of 101 participants were submitted to brain imaging and neuropsychological testing. Among these, 60 participants received the same set of imaging and neuropsychological tasks 24-36 months after the first set (phase II). In this article, we present a preliminary analysis performed on ten subjects from groups I and II and nine subjects from group III: activation (verbal fluency task) induced a specific pattern of increase in HMPAO retention (including BA 9/10, BA 18 bilaterally and right BA 17). In contrast to controls, in nine AD subjects no significant differences in HMPAO retention were observed when comparing activation and basal conditions. The cellular and molecular mechanisms that underlie the retention of HMPAO, the tracer used for single photon emission computed tomography (SPECT) imaging, has been studied in vitro in purified preparations of neurons and astrocytes with the aim of investigating the contribution of different cell types to hexamethyl-propyleneamineoxime labeled with technetium-99m (99mTc-HMPAO) retention in vitro. Results show that 99mTc-HMPAO retention predominates in astrocytes over neurons by a factor of approximately 2.5. Diethyl maleate, ethacrynic acid and buthionine sulfoximine, three agents which significantly reduce glutathione levels, also decreased 99mTc-HMPAO retention in both astrocytes and in neurons. Decrease did not always correlate with glutathione levels however, thus suggesting that other factors could be involved. The data presented indicate that astrocytes might constitute a prominent site of 99mTc-HMPAO retention and most likely contribute significantly to the SPECT signal. In addition, they also suggest that specific alterations in glial cell metabolism could explain flow-independent changes in 99mTc-HMPAO retention in the brain as observed by SPECT in certain pathologies (including Alzheimers disease). In particular, these observations suggest a key role of astrocytes in the signal detected with the imaging procedure, which is altered in the Alzheimers cohort subjected to the verbal fluency activation task.

Negative neurofunctional effects of frequency, depth and environment in recreational scuba diving: the Geneva “memory dive” study

Objectives: To explore relationships between scuba diving activity, brain, and behaviour, and more specifically between global cerebral blood flow (CBF) or cognitive performance and total, annual, or last 6 months’ frequencies, for standard dives or dives performed below 40 m, in cold water or warm sea geographical environments. Methods: A prospective cohort study was used to examine divers from diving clubs around Lac Léman and Geneva University Hospital. The subjects were 215 healthy recreational divers (diving with self-contained underwater breathing apparatus). Main outcome measures were: measurement of global CBF by 133Xe SPECT (single photon emission computed tomography); psychometric and neuropsychological tests to assess perceptual-motor abilities, spatial discrimination, attentional resources, executive functioning, and memory; evaluation of scuba diving activity by questionnaire focusing on number and maximum depth of dives and geographical site of the diving activity (cold water v warm water); and body composition analyses (BMI). Results: (1) A negative influence of depth of dives on CBF and its combined effect with BMI and age was found. (2) A specific diving environment (more than 80% of dives in lakes) had a negative effect on CBF. (3) Depth and number of dives had a negative influence on cognitive performance (speed, flexibility and inhibition processing in attentional tasks). (4) A negative effect of a specific diving environment on cognitive performance (flexibility and inhibition components) was found. Conclusions: Scuba diving may have long-term negative neurofunctional effects when performed in extreme conditions, namely cold water, with more than 100 dives per year, and maximal depth below 40 m.

EEG alpha activity reflects motor preparation rather than the mode of action selection

Alpha-band activity (8–13 Hz) is not only suppressed by sensory stimulation and movements, but also modulated by attention, working memory and mental tasks, and could be sensitive to higher motor control functions. The aim of the present study was to examine alpha oscillatory activity during the preparation of simple left or right finger movements, contrasting the external and internal mode of action selection. Three preparation conditions were examined using a precueing paradigm with S1 as the preparatory and S2 as the imperative cue: Full, laterality instructed by S1; Free, laterality freely selected and None, laterality instructed by S2. Time-frequency (TF) analysis was performed in the alpha frequency range during the S1–S2 interval, and alpha motor-related amplitude asymmetries (MRAA) were also calculated. The significant MRAA during the Full and Free conditions indicated effective external and internal motor response preparation. In the absence of specific motor preparation (None), a posterior alpha event-related desynchronization (ERD) dominated, reflecting the main engagement of attentional resources. In Full and Free motor preparation, posterior alpha ERD was accompanied by a midparietal alpha event-related synchronization (ERS), suggesting a concomitant inhibition of task-irrelevant visual activity. In both Full and Free motor preparation, analysis of alpha power according to MRAA amplitude revealed two types of functional activation patterns: (1) a motor alpha pattern, with predominantly midparietal alpha ERS and large MRAA corresponding to lateralized motor activation/visual inhibition and (2) an attentional alpha pattern, with dominating right posterior alpha ERD and small MRAA reflecting visuospatial attention. The present results suggest that alpha oscillatory patterns do not resolve the selection mode of action, but rather distinguish separate functional strategies of motor preparation.

The Influence of Time of Testing on Interference, Working Memory, Processing Speed, and Vocabulary: Age Differences in Adulthood

This research examines the effect of time of testing on adult age differences in resistance to interference, working memory, processing speed, and vocabulary. Results show that time of testing modulates age-related differences only in the ability to resist automatic and prepotent responses. Older adults tested in the afternoon were more susceptible to interference than young adults tested at the same time of the day, and than their peers tested in the morning. In contrast, age-related differences in working memory, processing speed, and vocabulary were not modulated by time of the day. Our findings suggest that age-related modulation of performance as a function of the time of the day is specific to resistance to interference.

The effect of age and individual differences in attentional control: A sample case using the Hayling test

Individual differences in working memory (WM) have been shown to reflect the ability to control attention in order to prevent interference. This study examines the role of WM capacity in resisting interference in the Hayling task, in samples of younger and older adults. In each age group, high and low WM span individuals had to complete high-cloze sentences with either expected words (initiation) or words providing no meaning to the sentences (interference). Results showed increased response times and decreased correct responses in interference, as compared to initiation. As interference increased, older adults demonstrated lower accuracy than younger ones. Further, low spans demonstrated higher interference costs than high spans on accuracy, while the reverse pattern was found for response times. Our findings suggest that both age and individual differences in WM capacity need to be considered to account for differences in the ability to resist to interference.

Early and automatic syntactic processing of person agreement

Mismatch negativity, an index of automatic cerebral activity in response to novel stimuli, was used to determine the onset of morphosyntactic processing in French. Stimuli were four two-word sentences made up of a pronoun (first or second person) and a verb (first or second person). Verb forms differed only in the inflectional suffix, which made the sentences either syntactically correct or incorrect. The mismatch negativity response was found to be modulated by the grammaticality of the agreement relation at 50–140 ms after inflection onset, corroborating the previous finding that morphosyntactic processing occurs early and out of the focus of attention. The role of the pronoun–suffix association probabilities in determining the observed timing of morphosyntactic processing is discussed.

Dépister la dénutrition chez la personne âgée bénéficiant de soins à domicile : une évaluation de la précision diagnostique des indicateurs issus du Resident Assessment Instrument - Home Care adapté pour la Suisse

INTRODUCTION in homecare practice, nurses are central actors for the screening of individuals at risks of undernutrition. CONTEXT in Switzerland, homecare nurses estimate the nutritional status of care recipients by means of a standardized geriatric assessment done with the RAI-HC. AIMS The aim of the study is to estimate the diagnostic accuracy of the « nutritional status » score, the body mass index and the weight loss documented from the RAI-HC. METHOD a sample of 267 homecare recipients aged 65 was assessed using the RAI-HC and the MNA-SF®. Sensitivity, specificity and area under the curve were estimated for the RAI-HC measures, with the MNA-SF® as the gold standard reference. RESULTS for the scores considered, sensitivity varied between 16.51 % and 68.81 %, specificity between 66.94 % and 99.37 %, and areas under the curve between 0.579 at 0.708. DISCUSSION the diagnostic accuracy of the RAI-HC indicators is not sufficient for an optimal screening of undernutrition in older homecare recipients. CONCLUSION an additional assessment with the MNA-SF® is recommended to optimize the early screening of individuals at risks of undernutrition.