Nathalie Fournet

Working memory functioning in medicated Parkinson's disease patients and the effect of withdrawal of dopaminergic medication

Cognitive impairments in Parkinsons disease (PD) could be explained by a central executive (CE) deficit in A. D. Baddeleys (1986) working memory model. To test this hypothesis, verbal, spatial, and double span tasks were given to 12 medicated PD patients and control participants, with varying recall delays. The double span task was assigned to explore the coordinating and integrating function of the CE, and lengthening the recall delay was expected to implicate more attentional resources. PD patients had lower spans relative to controls in all tasks. However, the more specific implication of the CE was difficult to prove. One reason could be that PD patients were on dopaminergic treatment when tested. To control this effect, 12 PD patients on and off medication were studied in a second experiment using the same tasks. PD patients off medication had lower spans only in the double task; this result underlines the role of dopamine on working memory processes.

Working memory in medicated patients with Parkinson's disease: the central executive seems to work.

OBJECTIVE--To determine whether a deficit of the central executive can explain the attentional deficits of patients with Parkinsons disease. METHODS--Fifteen patients with idiopathic Parkinsons disease and 15 controls were given a dual task paradigm minimising motor demands and combining verbal, visual, or spatial span with two conditions of articulatory suppression. RESULTS--Although the spans were systematically lower in medicated parkinsonian patients than in controls, suggesting a decrease of central processing resources, there was no direct evidence for a deficit of the central executive. CONCLUSIONS--A deficit of the central executive either is not an inevitable feature of the disease, or is dependent on the nature of task (visuomotor v cognitive), or is corrected by dopaminergic medication.

Functional MRI evidence for the decline of word retrieval and generation during normal aging

This fMRI study aimed to explore the effect of normal aging on word retrieval and generation. The question addressed is whether lexical production decline is determined by a direct mechanism, which concerns the language operations or is rather indirectly induced by a decline of executive functions. Indeed, the main hypothesis was that normal aging does not induce loss of lexical knowledge, but there is only a general slowdown in retrieval mechanisms involved in lexical processing, due to possible decline of the executive functions. We used three tasks (verbal fluency, object naming, and semantic categorization). Two groups of participants were tested (Young, Y and Aged, A), without cognitive and psychiatric impairment and showing similar levels of vocabulary. Neuropsychological testing revealed that older participants had lower executive function scores, longer processing speeds, and tended to have lower verbal fluency scores. Additionally, older participants showed higher scores for verbal automatisms and overlearned information. In terms of behavioral data, older participants performed as accurate as younger adults, but they were significantly slower for the semantic categorization and were less fluent for verbal fluency task. Functional MRI analyses suggested that older adults did not simply activate fewer brain regions involved in word production, but they actually showed an atypical pattern of activation. Significant correlations between the BOLD (Blood Oxygen Level Dependent) signal of aging-related (A > Y) regions and cognitive scores suggested that this atypical pattern of the activation may reveal several compensatory mechanisms (a) to overcome the slowdown in retrieval, due to the decline of executive functions and processing speed and (b) to inhibit verbal automatic processes. The BOLD signal measured in some other aging-dependent regions did not correlate with the behavioral and neuropsychological scores, and the overactivation of these uncorrelated regions would simply reveal dedifferentiation that occurs with aging. Altogether, our results suggest that normal aging is associated with a more difficult access to lexico-semantic operations and representations by a slowdown in executive functions, without any conceptual loss.

Phonological similarity in free and serial recall: The effect of increasing retention intervals

The phonological similarity effect (or acoustic confusion effect) consists of poor serial recall performance for lists composed of similar‐sounding words compared to lists of dissimilar‐sounding items. Building on the work of Nairne and Kelley (1999), the extent to which this classical verbal short‐term memory effect changes over the course of a retention interval was investigated. The impact of the phonological similarity on memory performance over time was compared in three paradigms: order reconstruction, serial recall, and free recall. Participants were presented with two blocks of 15 lists composed of five monosyllabic words, one block containing phonologically similar words and the other phonologically distinct words. Recall occurred either after 2, 8, or 24 seconds retention interval filled with a digit shadowing task. Our results confirmed and extended those of Nairne and Kelley. In order reconstruction and serial recall tasks, a classical phonological similarity effect (i.e., decrement in perform...

Evaluating short-term and working memory in older adults: French normative data

Short-term and working memory (WM) capacities are subject to change with ageing, both in normal older adults and in patients with degenerative or non-degenerative neurological disease. Few normative data are available for comparisons of short-term and WM capacities in the verbal, spatial and visual domains. To provide researchers and clinicians with a set of standardised tasks that assess short-term and WM using verbal and visuospatial materials, and to present normative data for that set of tasks. The present study compiled normative French data for three short-term memory tasks (verbal, visual and spatial simple span tasks) and two WM tasks (verbal and spatial complex span tasks) obtained from 445 healthy older adults aged between 55 and 85 years. Our data reveal main effects of age, education level and gender on older adults’ short-term and WM performances. Equation-based normalisation can therefore be used to take these factors into account. The results provide a set of cut-off scores for five standardised tasks that can be used to determine the presence of short-term or WM impairment in older adults.

Assessment of everyday executive functioning in children with frontal or temporal epilepsies

Executive functions are particularly vulnerable in case of brain disruption during childhood, when the brain is not fully mature. Some studies showed impairments of executive functions in children with epilepsy, but only a few of them investigated the impact of executive dysfunctions on daily life. The aim of this study was to understand the everyday executive functioning of children with epilepsy both at home and in school. We administered the Behavior Rating Inventory of Executive Function to parents and teachers of 53 children (7-16 years of age) with structural epilepsies or epilepsies of unknown cause of temporal lobe (n=25) or frontal lobe (n=28). The results indicated a global executive impairment in the whole group of patients, compared with normative data, with no difference between the group with temporal lobe epilepsy (TLE) and that with frontal lobe epilepsy (FLE), except for monitor domain, which seemed more frequently impaired in the group with FLE. Congruence between parent and teacher ratings was found. The frequency of seizures was not related to executive dysfunction, whereas the number of antiepileptic drugs tended to positively correlate with working memory impairment. Onset of epilepsy at a younger age was also related to more executive difficulties but only according to teacher ratings. Lastly, duration of epilepsy was strongly associated with executive deficits reported in the context of school. Our results support the executive dysfunction hypothesis in daily life of children with structural focal epilepsy or focal epilepsy of unknown cause and are consistent with the early brain vulnerability hypothesis currently prevalent in the context of child neuropsychology. The BRIEF appears to be a clinically useful tool for assessing executive function impairment in this clinical population.

The phonological loop in medicated patients with Parkinson's disease: presence of phonological similarity and word length effects.

OBJECTIVE: To test the verbal subsystem of Baddeleys working memory model (the phonological loop) in patients with Parkinsons disease. METHODS: Fifteen patients with idiopathic Parkinsons disease and 15 controls were tested with a span paradigm to assess the effects reflecting the functioning of the phonological loop: the phonological similarity effect (in verbal and visual presentation), and the word length effect (in visual presentation). RESULTS AND CONCLUSIONS: The patients did not show any dysfunction of the phonological loop, reflected by the presence of phonological similarity and word length effects, but had lower spans than controls. The implications of these results for the working memory model are discussed.

Multigroup confirmatory factor analysis and structural invariance with age of the Behavior Rating Inventory of Executive Function (BRIEF)--French version.

The parent and teacher forms of the French version of the Behavioral Rating Inventory of Executive Function (BRIEF) were used to evaluate executive function in everyday life in a large sample of healthy children (N = 951) aged between 5 and 18. Several psychometric methods were applied, with a view to providing clinicians with tools for score interpretation. The parent and teacher forms of the BRIEF were acceptably reliable. Demographic variables (such as age and gender) were found to influence the BRIEF scores. Confirmatory factor analysis was then used to test five competing models of the BRIEFs latent structure. Two of these models (a three-factor model and a two-factor model, both based on a nine-scale structure) had a good fit. However, structural invariance with age was only obtained with the two-factor model. The French version of the BRIEF provides a useful measure of everyday executive function and can be recommended for use in clinical research and practice.

Ecological approach of executive functions using the Behavioural Assessment of the Dysexecutive Syndrome for Children (BADS-C): Developmental and validity study

Introduction. Ecological assessment of executive functions (EF) with tasks simulating everyday-life difficulties in children remains poorly developed. The Behavioural Assessment of the Dysexecutive Syndrome for Children (BADS-C) is one of the rare tools proposed in this perspective, for which developmental and convergent validity are, however, rather limited. The objectives of this study were to explore EF development using the BADS-C, while considering the effect of gender and parental education as well as controversial relationships between intelligence and EF. We also aimed to examine to what extent the BADS-C could reflect EF of children in everyday life, as reported by their parents on questionnaires. Method. A group of 120 healthy children aged from 7 to 12 years was recruited. Their executive performance was examined by means of the BADS-C, and their intellectual efficiency was tested with the Wechsler intelligence scales. Rating of EF in everyday life was simultaneously carried out by children’s parents, using two questionnaires: the Dysexecutive Questionnaire for Children (DEX-C) of the BADS-C and the Behavior Rating Inventory of Executive Function (BRIEF). Results. Results showed a significant effect of age on BADS-C subtests, with inconsistencies from one subtest to another. Gender effect on EF performance was nonsignificant. Weak correlations were found between EF scores and parental education or intelligence quotient. Lastly, while the two questionnaires of everyday-life EF were strongly correlated with each other, their links with BADS-C subtests scores were weak. Conclusions. This study shows differentiated developmental curves on BADS-C, reflecting a variable implication of executive resources according to subtests. The limited relations between BADS-C performance and sociodemographic variables or IQ could be due to the fact that executive difficulties are moderate in healthy children at this age. Moreover, the capacity of the BADS-C to reflect EF as perceived by the child’s relatives in everyday life remains questionable.

Behavioral evidence for a differential modulation of semantic processing and lexical production by aging: a full linear mixed-effects modeling approach.

ABSTRACT The effect of normal aging on lexical production and semantic processing was evaluated in 72 healthy participants. Four tasks were used, picture naming (PN), picture categorization (PC), numerical judgment (NJ), and color judgment (CJ). The dependence of reaction time (RT) and correct responses with age was accounted by mixed-effects models. Participants underwent neuropsychological testing for verbal, executive, and memory functions. The RTs increase significantly with age for all tasks. After parceling out the non-specific cognitive decline, as reflected by the NJ task, the RT for the PN task decreases with age. Behavioral data were interpreted in relation with neuropsychological scores. Our results suggest that (a) naming becomes more automatic and semantic processing slightly more difficult with age, and (b) a non-specific general slowdown of cognitive processing occurs with age. Lexical production remained unaltered, based on compensatory automatic processes. This study also suggests a possible slowdown of semantic processing, even in normal aging.