Spatial exploration and navigation in Down syndrome and Williams syndrome.

We know little about the ability to explore and navigate large-scale space for people with intellectual disability (ID). In this cross-syndrome study, individuals with Down syndrome (DS), individuals with Williams syndrome (WS) and typically developing children (TD; aged 5-11 years) explored virtual environments with the goal of learning where everything was within the environment (Experiment 1) or to find six stars (Experiment 2). There was little difference between the WS and DS groups when the goal was simply to learn about the environment with no specific destination to be reached (Experiment 1); both groups performed at a level akin to a subset of TD children of a similar level of non-verbal ability. The difference became evident when the goal of the task was to locate targets in the environment (Experiment 2). The DS group showed the weakest performance, performing at or below the level of a subset of TD children at a similar level of non-verbal ability, whilst the WS group performed at the level of the TD subset group. The DS, WS and TD group also demonstrated different patterns of exploration behavior. Exploration behaviour in DS was weak and did not improve across trials. In WS, exploration behavior changed across trials but was atypical (the number of revisits increased with repeated trials). Moreover, transdiagnostic individual difference analysis (Latent Profile Analysis) revealed five profiles of exploration and navigation variables, none of which were uniquely specific to DS or to WS. Only the most extreme profile of very poor navigators was specific to participants with DS and WS. Interestingly, all other profiles contained at least one individual with DS and at least one individual with WS. This highlights the importance of investigating heterogeneity in the performance of individuals with intellectual disability and the usefulness of a data-driven transdiagnostic approach to identifying behavioral profiles.

Description of Routes in People With Intellectual Disability.

The ability to describe routes was assessed in participants with intellectual disability (ID) and participants without ID matched on chronological age (CA) or on mental age (MA). In two experiments, participants learned a route through a virtual environment until they reached a learning criterion. They were then asked to externalize their spatial knowledge in a verbal description task, a landmark recognition task, or a map completion task. Results revealed that participants with ID mainly described the route as a succession of actions ("turn left"), and participants in the CA group prescribed actions referring to a landmark ("turn left at the swing"). Yet, results from the other tasks showed that people with ID had good landmark knowledge of the environment.

The development of route learning in Down syndrome, Williams syndrome and typical development: investigations with virtual environments.

The ability to navigate new environments has a significant impact on the daily life and independence of people with learning difficulties. The aims of this study were to investigate the development of route learning in Down syndrome (N = 50), Williams syndrome (N = 19), and typically developing children between 5 and 11 years old (N = 108); to investigate use of landmarks; and to relate cognitive functions to route-learning ability in these groups. Overall, measures of attention and long-term memory were strongly associated with route learning, even once non-verbal ability was controlled for. All of the groups, including 5- to 6-year-old TD children, demonstrated the ability to make use of all landmark types to aid route learning; those near junctions, those further from junctions, and also distant landmarks (e.g. church spire, radio mast). Individuals with WS performed better than a matched subset of TD children on more difficult routes; we suggest that this is supported by relatively strong visual feature recognition in the disorder. Participants with DS who had relatively high levels of non-verbal ability performed at a similar level to TD participants.

Route knowledge and configural knowledge in typical and atypical development: a comparison of sparse and rich environments.

BACKGROUND: Individuals with Down syndrome (DS) and individuals with Williams syndrome (WS) have poor navigation skills, which impact their potential to become independent. Two aspects of navigation were investigated in these groups, using virtual environments (VE): route knowledge (the ability to learn the way from A to B by following a fixed sequence of turns) and configural knowledge (knowledge of the spatial relationships between places within an environment). METHODS: Typically developing (TD) children aged 5 to 11 years (N = 93), individuals with DS (N = 29) and individuals with WS (N = 20) were presented with a sparse and a rich VE grid maze. Within each maze, participants were asked to learn a route from A to B and a route from A to C before being asked to find a novel shortcut from B to C. RESULTS: Performance was broadly similar across sparse and rich mazes. The majority of participants were able to learn novel routes, with poorest performance in the DS group, but the ability to find a shortcut, our measure of configural knowledge, was limited for all three groups. That is, 59 % TD participants successfully found a shortcut, compared to 10 % participants with DS and 35 % participants with WS. Differences in the underlying mechanisms associated with route knowledge and configural knowledge and in the developmental trajectories of performance across groups were observed. Only the TD participants walked a shorter distance in the last shortcut trial compared to the first, indicative of increased configural knowledge across trials. The DS group often used an alternative strategy to get from B to C, summing the two taught routes together. CONCLUSIONS: Our findings demonstrate impaired configural knowledge in DS and in WS, with the strongest deficit in DS. This suggests that these groups rely on a rigid route knowledge based method for navigating and as a result are likely to get lost easily. Route knowledge was also impaired in both DS and WS groups and was related to different underlying processes across all three groups. These are discussed with reference to limitations in attention and/or visuo-spatial processing in the atypical groups.

Assessing apathy in everyday clinical practice with the short-form Lille Apathy Rating Scale.

BACKGROUND: Apathy is an invalidating behavioral disorder that must always be screened for and assessed in patients with Parkinson's disease (PD). The Lille Apathy Rating Scale (LARS) has been validated in several different contexts, but the lengthy administration time means that it is mostly recommended for research use. The aim of the present study was to validate a short form of the LARS for use in everyday practice. METHODS: In total, 416 patients with PD and 56 healthy controls participated in the study. Apathy, depression, motor symptoms, and overall cognitive efficiency were assessed. The most discriminant items of the LARS for apathy detection were selected using multiple indicators. RESULTS: A subset of 12 items (constituting the short-form LARS) showed the best convergence. Concurrent and criterion-related validity, internal consistency, test-retest reliability, and inter-rater reliability were very good. CONCLUSIONS: The short-form LARS is a reliable, practical, patient interview-based instrument for assessing apathy in everyday clinical practice.

Wayfinding behaviour in Down syndrome: a study with virtual environments.

The aim of this study was to assess wayfinding abilities in individuals with Down syndrome (DS). The ability to learn routes though a virtual environment (VE) and to make a novel shortcut between two locations was assessed in individuals with DS (N=10) and control participants individually matched on mental age (MA) or chronological age (CA). The results showed that most of the participants with DS were able to learn routes through the VE, even though they needed more trials than the CA controls to reach the learning criterion. However, they did not show flexible wayfinding behaviour because they were unable to find a shortcut between two known locations (unlike the CA controls). The results suggest that most individuals with DS can acquire knowledge about specific routes, but are unable to integrate that knowledge into a configurational understanding of the environment.

Short-term memory, executive control, and children's route learning.

The aim of this study was to investigate route-learning ability in 67 children aged 5 to 11years and to relate route-learning performance to the components of Baddeley's model of working memory. Children carried out tasks that included measures of verbal and visuospatial short-term memory and executive control and also measures of verbal and visuospatial long-term memory; the route-learning task was conducted using a maze in a virtual environment. In contrast to previous research, correlations were found between both visuospatial and verbal memory tasks-the Corsi task, short-term pattern span, digit span, and visuospatial long-term memory-and route-learning performance. However, further analyses indicated that these relationships were mediated by executive control demands that were common to the tasks, with long-term memory explaining additional unique variance in route learning.

Route learning and shortcut performance in adults with intellectual disability: a study with virtual environments.

The ability to learn routes though a virtual environment (VE) and to make a novel shortcut between two locations was assessed in 18 adults with intellectual disability and 18 adults without intellectual disability matched on chronological age. Participants explored two routes (A ⇔ B and A ⇔ C) until they reached a learning criterion. Then, they were placed at B and were asked to find the shortest way to C (B ⇔ C, five trials). Participants in both groups could learn the routes, but most of the participants with intellectual disability could not find the shortest route between B and C. However, the results also revealed important individual differences within the intellectual disability group, with some participants exhibiting more efficient wayfinding behaviour than others. Individuals with intellectual disability may differ in the kind of spatial knowledge they extract from the environment and/or in the strategy they use to learn routes.

Apathy may herald cognitive decline and dementia in Parkinson's disease.

Apathy is usually defined as a lack of motivation. It may occur as part of another disorder (notably depression and dementia) or as an isolated syndrome. In Parkinson's disease (PD), apathy is common and several studies have reported an association between this condition and more severe cognitive symptoms, such as executive dysfunction. However, this association has not been thoroughly investigated. The aim of this study (in nondepressed, nondemented PD patients) was to examine whether or not cognitive decline and/or dementia occurred more frequently in apathetic subjects than in nonapathetic subjects. Forty consecutive PD patients participated in the study (20 with apathy and 20 without). None of the subjects were either demented or depressed at the time of study entry. The patients' cognitive functions were extensively assessed twice: at study entry and after an 18-month follow-up period. At study entry, the apathetic PD patients had significantly lower global cognitive status and executive function scores than the nonapathetic subjects. After a median period of 18 months, the rate of conversion to dementia was found to be significantly higher in the apathetic group than in the nonapathetic group (8 of 20 and 1 of 20, respectively). Even in nondemented patients, the decrease over time in cognitive performance (mainly executive function but also memory impairment) was significantly greater in apathetic subjects than in nonapathetic subjects. These findings suggest that in nondemented, nondepressed PD patients, apathy may be a predictive factor for dementia and cognitive decline over time.

The Lille Apathy Rating Scale: validation of a caregiver-based version.

Apathy is reported in 16.5% to 70% of Parkinson's disease (PD) patients. Our recently developed Lille Apathy Rating Scale (LARS) has been specifically validated for patient-based assessment of apathy in PD. The aim of the present study was to validate a caregiver-based version of the LARS. Sixty consecutive PD patients and their respective caregivers participated in the study. An informant-based version of the LARS (LARS-i) was developed to rate apathy via a caregiver-based structured interview. Apathy was also assessed in a patient-based interview using the LARS and the informant- and clinician-rated versions of the Apathy Evaluation Scale (AES). Cronbach's alpha and standardized alpha coefficients were 0.872 and 0.877, respectively, and the split-half reliability was 0.901 (revealing good internal consistency). The test-retest and inter-rater reliability values were 0.960 and 0.996, respectively. Criterion-related validity (according to an independent, expert diagnosis) was good. Scores on the LARS and the LARS-i were highly correlated. However, apathy was rated significantly more severely by the caregiver than by the patient. This difference was significantly higher for demented than nondemented PD patients. The LARS-i was seen to have excellent psychometric properties and appears to be valid for use in PD with respect to the patient-based LARS and the informant- and clinician-rated versions of the AES.

Characteristics of apathy in Parkinson's disease.

The objective of this study was to use the Lille Apathy Rating Scale to assess apathy in a large population of Parkinson's disease (PD) patients and identify several different apathy profiles. One hundred fifty-nine patients with probable PD and 58 healthy controls participated in the study. Apathy was assessed using the Lille Apathy Rating Scale. Motor, cognitive, and depressive symptoms were rated on standardized scales. Data were analyzed using linear regression and multivariate analyses of variance. Thirty-two percent of the PD patients were classified as apathetic. Apathy was more frequent in patients with dementia. The four apathy dimensions contributed differently to the overall severity of the apathetic condition. Action initiation and intellectual curiosity had a marked influence. Linear regression analysis revealed that the apathy level was mainly determined by cognitive impairment, not associated with the severity of motor symptoms, and only associated with the apathy subcomponent of the Montgomery and Asberg Depression Rating Scale. Apathy is highly prevalent in PD patients. Apathy profiles vary according to the clinical presentation of PD. The high prevalence of apathy in PD suggests the involvement of frontal-subcortical circuits. Although the neurochemical substrate of apathy remains poorly characterized, the strong link between apathy and cognitive impairment observed in several studies suggests the participation of nondopaminergic circuits.

[Development of an experimental methodology: hypotheses and variables]. / Mise en place d'une méthodologie expérimentale: hypotheses et variables.

In this methodological paper, we present the elaboration of the experimental design, central stage of the research cycle. First, we focus on the hypothesis elaboration from the research question. Then, we detail the hypothesis operationalisation by the means of the choice of variables. Finally, the experimental controls and the factorial designs are presented.