Assessment of Executive Functions in Prader-Willi Syndrome and Relationship with Intellectual Level

Conceptualization of the term "ecological validity" in neuropsychological research on executive function assessment: a systematic review and call to action

OBJECTIVE

"Ecological validity" (EV) is classically defined as test's ability to predict real-world functioning, either alone or together with test's similarity to real-world tasks. In neuropsychological literature on assessment of executive functions (EF), EV is conceptualized inconsistently, leading to misconceptions about the utility of tests. The goal of this systematic review was to examine how EV is conceptualized in studies of EF tests described as ecologically valid.

METHOD

MEDLINE and PsychINFO Databases were searched. PRISMA guidelines were observed. After applying inclusion and exclusion criteria, this search yielded 90 articles. Deductive content analysis was employed to determine how the term EV was used.

RESULTS

About 1/3 of the studies conceptualized EV as the test's ability to predict functional outcomes, 1/3 as both the ability to predict functional outcome and similarity to real-world tasks, and 1/3 were either unclear about the meaning of the term or relied on notions unrelated to classical definitions (e.g., similarity to real-world tasks alone, association with other tests, or the ability to discriminate between populations).

CONCLUSIONS

Conceptualizations of the term EV in literature on EF assessment vary grossly, subsuming the notions of criterion, construct, and face validity, as well as sensitivity/specificity. Such inconsistency makes it difficult to interpret clinical utility of tests that are described as ecologically valid. We call on the field to require that, at minimum, the term EV be clearly defined in all publications, or replaced with more concrete terminology (e.g., criterion validity).

A pilot rating system to evaluate the quality of goal attainment scales used as outcome measures in rehabilitation

Goal Attainment Scaling (GAS) is a method for writing person-centred approach evaluation scales that can be used as an outcome measure in clinical or research settings in rehabilitation. To be used in a research setting, it requires a high methodological quality approach. The aim of this study was to explore the feasibility and reliability of the GAS quality rating system, to ensure that GAS scales used as outcome measures are valid and reliable. Secondary objectives were: (1) to compare goal attainment scores' reliability according to how many GAS levels are described in the scale; and (2) to explore if GAS scorings are influenced by who scores goal attainment. The GAS scales analysed here were set collaboratively by 57 cognitively impaired adults clients and their occupational therapist. Goals had to be achieved within an inpatient one-month stay, during which clients participated in an intervention aimed at improving planning skills in daily life. The GAS quality rating system proved to be feasible and reliable. Regarding GAS scores, interrater reliability was higher when only three of the five GAS levels were described, i.e., "three milestone GAS" (0.74-0.92), than when all five levels were described (0.5-0.88), especially when scored by the clients (0.5 -0.88).

Associations between executive functions, intelligence and adaptive behaviour in children and adolescents with mild intellectual disability

Background: The purpose of this study was to explore the role of everyday executive functions in relation to intelligence and adaptive behaviour in children and adolescents with mild intellectual disability. Method: A group of children and adolescents, previously diagnosed with mild intellectual disability were assessed according to intelligence, everyday executive functions and adaptive behaviour. The association between everyday executive functions and intelligence was examined, and it was explored whether intelligence or everyday executive functions would best predict adaptive behaviour. Results: Adaptive behaviour was significantly predicted by executive functions, but not by intelligence. Nor was intelligence significantly related to everyday executive functions in this group. Conclusions: Although fundamental in diagnosing intellectual disability, intelligence cannot predict adaptive behaviour. Assessing everyday executive functions and adaptive behaviour, as well as acknowledging the strong association between them, provides valuable information in the process of optimizing developmental support for children and adolescents with mild intellectual disability.

Improvement of Planning Abilities in Adults with Prader-Willi Syndrome: A Randomized Controlled Trial

Prader-Willi Syndrome (PWS) is a neurodevelopmental genetic disorder with executive deficits. Planning is one of the impaired executive functions implied in the regulation of behavior and everyday actions. We aimed to explore the feasibility and the effectiveness of a metacognitive strategy training designed to improve planning in adults with PWS using a double-blind between-group (training versus usual care) randomized controlled trial, with computerized tests and paper-pencil ecological outcome measures targeting planning, other executive functions, and achievement of personalized goal. Results showed better performances in several executive tasks and in achievement of personalized goals after both interventions, but better improvement for the experimental group (n = 27) compared to control (n = 26) only on the task assessing planning abilities. Interviews with occupational therapists demonstrated the feasibility of this training with this population. Despite a small number of sessions, the metacognitive strategy training showed encouraging results on planning abilities of patients.

Study of the deficit in planning abilities of adults with Prader-Willi Syndrome

BACKGROUND

Prader-Willi syndrome (PWS) is a complex developmental genetic disorder associated with intellectual disability and deficits in executive functions which result in disorganisation and poor personal autonomy.

AIMS

This study aimed to determine impairments in planning skills of adults with PWS, in relation with their intellectual disabilities, as well as the influence of food compulsions on their performance.

METHODS AND PROCEDURES

A modified version of the Zoo Map from the Behavioural Assessment of the Dysexecutive Syndrome was used in three groups: a group of adults with PWS in comparison with two groups both matched on chronological age, one with typical development (TD) and one with intellectual disability (ID).

OUTCOMES AND RESULTS

Compared to TD adults, both adults with PWS and ID showed increased planning time and lower raw scores on the planning task. The execution time and the number of errors were higher in the PWS group compared to the comparison groups. All three groups performed worse in the non-food condition only for number of errors and raw score.

CONCLUSIONS AND IMPLICATIONS

Planning abilities were impaired in PWS adults. Results also showed that intellectual level plays a role in participants' performance. These findings are essential to understand the difficulties of people with PWS daily life.

A cross-comparison of cognitive ability across 8 genomic disorders

Genomic disorders result from rearrangement of the human genome. Most genomic disorders are caused by copy number variants (CNV), deletions or duplications of several hundred kilobases. Many CNV loci are associated with autism, schizophrenia, and most commonly, intellectual disability (ID). However, there is little comparison of cognitive ability measures across these CNV disorders. This study aims to understand whether existing data can be leveraged for a cross-comparison of cognitive ability among multiple CNV. We found there is a lack of harmonization among assessment instruments and little standardization for reporting summary data across studies. Despite these limitations, we identified a differential impact of CNV loci on cognitive ability. Our data suggest that future cross-comparisons of CNV disorders will reveal meaningful differences across the phenotypic spectrum, especially if standardized phenotypic assessment is achieved.

Executive Functions and Attention Processes in Adolescents and Young Adults with Intellectual Disability

(1) Background: We made a comprehensive evaluation of executive functions (EFs) and attention processes in a group of adolescents and young adults with mild intellectual disability (ID). (2) Methods: 27 adolescents and young adults (14 females and 13 males) with ID, aged between 15.1 and 23 years (M = 17.4; SD = 2.04), were compared to a control group free of cognitive problems and individually matched for gender and age. (3) Results: As for EFs, individuals with ID were severely impaired on all subtests of the Behavioral Assessment of Dysexecutive Syndrome (BADS) battery. However, we also found appreciable individual differences, with eight individuals (approximately 30%) scoring within normal limits. On the attention tests, individuals with ID were not generally slower but presented specific deficits only on some attention tests (i.e., Choice Reaction Times, Color Naming and Color–Word Interference, and Shifting of Attention for Verbal and for Visual Targets).The role of a global factor (i.e., cognitive speed) was modest in contributing to the group differences; i.e., when present, group differences were selectively associated with specific task manipulations, not global differences in cognitive speed. (4) Conclusions: The study confirmed large group differences in EFs; deficits in attentional processing were more specific and occurred primarily in tasks taxing the selective dimension of attention, with performance on intensive tasks almost entirely spared.

Cognitive Training Targeting Planning Dysfunction in Adults with Prader-Willi Syndrome: Brief Report of a Study Protocol

Background: Prader-Willi syndrome (PWS) is a neurodevelopmental genetic disorder involving executive deficits notably with planning. The main objective of the study is to assess the effectiveness of cognitive training on daily life planning difficulties in PWS patients. Methods/design: The study is a double-blind randomized controlled trial which will compare the effectiveness of a metacognitive strategy intervention designed to improve planning difficulties for PWS patients to usual occupational therapy. Sixty adults will be included over 20 months. The main outcome measure will be the performance on the Modified Six Elements Test from the BADS; secondary outcome measures will be computerized executive tasks and questionnaires. Daily life planning difficulties will be identified and transformed into measurable goals using Goal Attainment Scaling. Discussion: The project will provide knowledge on the difficulties experienced by PWS patients, in relation to their executive functioning in order to implement effective intervention for planning in daily life.

Investigation of the relationship between electrodermal and behavioural responses to executive tasks in Prader-Willi syndrome: An event-related experiment

BACKGROUND

Recent work suggests that maladaptive behaviors in genetic developmental disorders may emerge from autonomic dysfunctions impacting higher order executive functions. In Prader-Willi syndrome (PWS), executive functions are not well understood and investigations of possible underlying causes at the autonomic level are lacking.

AIMS

This study aimed at clarifying the status of inhibition and working memory updating functions in PWS and searched for sympathetic signatures as well as to examine their links with executive performance.

METHODS AND PROCEDURES

The performance of thirty adults with PWS was compared to that of thirty healthy adults on two tasks assessing inhibition and working memory updating while electrodermal activity (EDA) was recorded.

OUTCOMES AND RESULTS

PWS adults underperformed healthy adults in the inhibition and the working memory updating tasks and showed abnormal skin conductance responses. Distinct EDA have been found in PWS and healthy adults. Furthermore, while EDA reflected distinct cognitive processes, correlations between electrodermal and behavioural data were absent when examining the two groups separately.

CONCLUSIONS AND IMPLICATIONS

PWS is associated with a slight impairment of inhibition and a severe impairment of working memory updating. Furthermore, there are specific sympathetic autonomic signatures in PWS that do not present straightforward links with executive dysfunctions.

Molecular Mechanisms of Oxytocin Signaling at the Synaptic Connection

Aberrant regulation of oxytocin signaling is associated with the etiology of neurodevelopmental disorders. Synaptic dysfunctions in neurodevelopmental disorders are becoming increasingly known, and their pathogenic mechanisms could be a target of potential therapeutic intervention. Therefore, it is important to pay attention to the role of oxytocin and its receptor in synapse structure, function, and neuron connectivity. An early alteration in oxytocin signaling may disturb neuronal maturation and may have short-term and long-term pathological consequences. At the molecular level, neurodevelopmental disorders include alterations in cytoskeletal rearrangement and neuritogenesis resulting in a diversity of synaptopathies. The presence of oxytocin receptors in the presynaptic and postsynaptic membranes and the direct effects of oxytocin on neuronal excitability by regulating the activity of ion channels in the cell membrane implicate that alterations in oxytocin signaling could be involved in synaptopathies. The ability of oxytocin to modulate neurogenesis, synaptic plasticity, and certain parameters of cytoskeletal arrangement is discussed in the present review.

Rigidity in routines and the development of resistance to change in individuals with Prader-Willi syndrome

BACKGROUND

Individuals with Prader-Willi syndrome (PWS) commonly show debilitating resistance to change, which has been linked to cognitive deficits in task switching. Anecdotal reports suggest that exposure to flexibility in routines during development may be beneficial for limiting subsequent resistance to change in people with PWS, which is consistent with a beneficial role of such exposure on the development of task switching, highlighted in typical children. Here, we aim to investigate the development of resistance to change in individuals with PWS and hypothesise that exposure to increased rigidity in routines will be associated with increased subsequent resistance to change.

METHODS

An author-compiled informant report interview and two previously validated questionnaires were administered to the caregivers of 10 individuals with PWS (5-23 years). The interview examined rigidity in routines and resistance to change across life stages defined by easily distinguishable events (before school, during primary school, during secondary school, after school, currently), using open-ended and structured yes/no and 5-point Likert questions. Open-ended data were coded using an author-compiled system. Responses from two additional informants and data from the questionnaires were used to assess inter-informant reliability and concurrent validity of the structured questions.

RESULTS

The validity of the interview was supported by acceptable inter-rater reliability of the open-ended coding system and inter-informant reliability, internal consistency and concurrent validity of structured questions. Descriptive analyses of ratings of behaviour change showed a pattern of increasing resistance to change over the life course for the four oldest individuals, who had all been exposed to substantial rigidity in routines before and during primary school. Furthermore, only one individual - currently in primary school - was exposed to very little rigidity in routines before and during primary school, and he had showed a decrease in resistance to change after entering primary school. Open-ended data showed that more individuals currently evidencing little resistance to change had been exposed to parent or self-imposed flexibility in routines, than those currently evidencing substantial resistance to change. However, correlational analyses on rigidity and resistance to change ratings highlighted the possibility that rigidity during primary school is most relevant for developing resistance to change. Finally, open-ended data emphasised an important beneficial role of rigidity in routines for limiting the current challenging behaviour of individuals with high resistance to change.

CONCLUSION

Because task switching appears to evidence a period of high developmental sensitivity during early primary school years, we propose that this period may represent a critical time when increasing flexibility in the routines of children with PWS could limit the development of resistance to change. However, a careful balance would need to be struck, given the apparent benefit of rigid routines on current behaviour. Further work in this area is much needed.

Executive functions and Prader-Willi syndrome: global deficit linked with intellectual level and syndrome-specific associations

The aim of this study was to support the growing evidence suggesting that Prader-Willi Syndrome (PWS) might present with an impairment of executive functions (EFs) and to investigate whether this impairment is specific to patients with PWS or due to their intellectual disability (ID). Six tasks were administered to assess EFs (inhibition, switching, updating, cognitive estimation, and planning) to 17 patients with PWS and 17 age-matched healthy individuals. Performance was significantly impaired in the PWS group on all EFs and after controlling for IQ level, intergroup differences remained only for switching and cognitive estimation. In conclusion, PWS seems to be associated with a global impairment of EFs that appears to be closely linked with intellectual impairment but also with the PWS itself.

Ontogenesis of oxytocin pathways in the mammalian brain: late maturation and psychosocial disorders

Oxytocin (OT), the main neuropeptide of sociality, is expressed in neurons exclusively localized in the hypothalamus. During the last decade, a plethora of neuroendocrine, metabolic, autonomic and behavioral effects of OT has been reported. In the urgency to find treatments to syndromes as invalidating as autism, many clinical trials have been launched in which OT is administered to patients, including adolescents and children. However, the impact of OT on the developing brain and in particular on the embryonic and early postnatal maturation of OT neurons, has been only poorly investigated. In the present review we summarize available (although limited) literature on general features of ontogenetic transformation of the OT system, including determination, migration and differentiation of OT neurons. Next, we discuss trajectories of OT receptors (OTR) in the perinatal period. Furthermore, we provide evidence that early alterations, from birth, in the central OT system lead to severe neurodevelopmental diseases such as feeding deficit in infancy and severe defects in social behavior in adulthood, as described in Prader-Willi syndrome (PWS). Our review intends to propose a hypothesis about developmental dynamics of central OT pathways, which are essential for survival right after birth and for the acquisition of social skills later on. A better understanding of the embryonic and early postnatal maturation of the OT system may lead to better OT-based treatments in PWS or autism.