Fundamental premises
The dissertation's title, "Atypical Paths to Knowledge Construction," specifies three fundamental aspects of the research project. First, the CHARGE genotype induces a pathophysiological chain of events from the embryonic stage onwards. Accordingly, the CHARGE ontogenesis is inherently atypical, a key feature of the current research project.
Second, the neuroconstructivist explanatory model of cognitive development rests on the constructive properties of neurobiological, cortical, and functional transactions that continually modify each other through instances of neural inductive sensorimotor experiential learning. Thus, cognitive change and progress occur through the dynamic merging of an overwhelming number of information units, eventually manifesting as a mental representation accessible for neuropsychological assessment.
Third, the research project primarily suggested that the cognitive challenges exhibited by individuals with CHARGE primarily stem from restricted sensorimotor access to neural-inducing experiences provided by their endogenous and exogenous environments.
Background
CHARGE (i.e., Coloboma of the eye; Heart disease; Atresia of the choanae; Retardation of growth and development; Genital hypoplasia; Ear anomalies and deafness) is a rare genetic disorder affecting large parts of the sensorimotor apparatus. Whereas the learning opportunities of neurotypical children accumulate through self-driven developmental processes (Campos, Nieto & Núñez, 2019), the combined auditory, visual, and vestibular impairments of individuals born with CHARGE modify both the quantity and quality of experiential learning. Thus, the meaning-making of children with CHARGE relies on a different set of information units than that of their peers, ultimately regulating processes of learning and interrelating. In cases where CHARGE also includes deafblindness, the basis for meaning-making is even more fragmented and fragile. Consequently, developmental opportunities for individuals with CHARGE are restricted from birth onwards, setting requirements on the environment to enforce individualised learning conditions that compensate for any sensorimotor barriers to learning.
Conceptually, the dissertation rests on neuroconstructivism and its explanatory model of knowledge construction, in which cognitive development is considered a product of self-organising cortical systems emerging from the dynamic transactions between levels of constraints induced by the individual’s genes and environment. From a neuroconstructivist stance, counteracting the effects of the sensorimotor barriers becomes the target of interventions.
Aims
The overarching goal of the research project was to gain a deeper understanding of the meaning-making and cognitive development of individuals with CHARGE and to disclose predictive factors and targets for interventions. Three clinical studies with complementary aims served this goal. Whereas Study I focused on different aspects of global intellectual abilities in CHARGE, Study II addressed their executive functioning. The last study (Study III) focused on the potential effect of sensorimotor impairments on the test performances of individuals with CHARGE, which would have consequences for the evaluation of both global intellectual abilities and executive functioning, as well as the choice of intervention targets.
Method
The research project employed a cross-sectional and population-based design, focusing on identifying predictors of global intellectual abilities and executive functions in the Norwegian population (N = 35) of individuals with CHARGE syndrome. Test performances from neuropsychological assessments provided the primary data set (dependent variables), and their sensorimotor characteristics (i.e., auditory, visual, and vestibular impairments) served as independent variables.
The main research hypothesis posited that the cognitive and adaptive behavioural deficits associated with CHARGE are multilevel, transactional outcomes induced by the CHARGE genotype and its environment and constrained by auditory, visual, and vestibular impairments, ultimately resulting in an atypical representation of how the world works. This statement was converted into three sub-hypotheses accessible for testing by three uniquely designed clinical studies. The sub-hypothesis of Study I, stating that “Individuals with atypical development are at increased risk of underestimation of intellectual ability”, was tested endorsing the national Norwegian guidelines for assessment of the diagnosis of intellectual disability. The procedure includes an evaluation of global intellectual ability and adaptive behaviour by standard psychometric methodology.
The sub-hypothesis of Study II, stating that “Executive functions of individuals with CHARGE have a distinct impact on development and learning”, was tested by a hierarchical design in which the first step investigated executive functioning according to a three-factor structure. The second step involved reorganising the sample into clinical subgroups according to symptom load to reveal associations between the degree of impairment and executive challenges. The sub-hypothesis of Study III, stating that “Individuals with CHARGE and deafblindness have equal cognitive potentials as those without deafblindness”, was tested by implementing a pre-post-test design, comparing test performances from norm-referenced assessment with achievements scores after manipulating the test condition by increased sensorimotor accessibility.
Main findings
Overall, the participants' test performances proved more valid than the findings from the report-based instruments. Simultaneously, answers and ratings on adaptive behavioural abilities and executive functioning implied a lower competency than what was indicated by test results, which also tended to deflate the performance-based scores.
The participant's achievement level, obtained through procedures designed for neurotypical populations, indicated global intellectual abilities within two standard deviations of the normative average when considered as a population. When dividing the performance level according to age, pre-schoolers deviated the most from their norm group, and adults deviated the least, with the group of adolescents falling in between.
The participants demonstrated significant executive dysfunction within mental flexibility and inhibition (below two standard deviations from the norm average). Working memory stood out as a specific cognitive strength, particularly for participants with deafblindness, whose working memory approached the normative average (within 1.5 standard deviations from the normative average).
Test performances further indicated that the participants had equal cognitive potential, regardless of their deafblindness.
The participants' auditory deficits had a significant impact on their performance level, and the auditory impairment was the primary contributor to cognitive level.
Discussion
The neuroconstructivist developmental approach to cognitive development concurred theoretically and empirically with the cognitive characteristics of individuals with CHARGE. In line with neuroconstructivism, the research project assumed that the knowledge construction and cognitive development of the Norwegian population of individuals with CHARGE were atypical and context dependent, constrained by the individual's dispositions (i.e., embodied) and environmental features (i.e., ensocialment). The paradigm also implies that children born with CHARGE may potentially follow the same path of progress as their neurotypical peers when accessing neural-inducing learning opportunities.
After considering random and systematic measurement errors, the participants' knowledge construction appeared dynamically atypical by nature, starting highly deviant compared to typical norm patterns and decreasing over developmental time into adulthood. Findings suggested that cognitive investigations using instruments based on populations with intact sensorimotor apparatus may compromise the validity of test scores for children and adolescents with CHARGE. However, since the adult participants revealed less atypical cognitive profiles, approximating neurotypical age norms, validity issues seem to diminish towards adulthood.
Overall, the participants' test performances indicated that composite scores of instruments evaluating global intellectual abilities and executive functioning tended to camouflage specifics within their knowledge construction. Information about cognitive strengths and challenges is essential when optimising special education plans and learning.
Compensating for some of the adverse effects of the participants' sensorimotor impairments during cognitive assessment had a significant positive effect on their performance level. The effect was most significant for participants with deafblindness, concurring with the assumption that sensory accessibility is a primary contributor to lowering performance levels. The finding indicated that cognitive evaluation following neurotypical procedures is unable to capture the (atypical) cognitive profiles of individuals with sensorimotor impairments and tends to underestimate their cognitive functioning and potential.
Context dependency emerged as a guiding principle for the developmental trajectory of the Norwegians with CHARGE, as test performances varied according to psychoemotional status, test conditions, and applied instruments. Furthermore, the constraints on the participants' knowledge construction included the degree of sensorimotor impairment, the presence of deafblindness, and executive functioning, implying targets of intervention when promoting learning and developmental.
Knowledge construction was also explicitly connected to age, as getting older entails access to different and more complex experiences. Revealing age as a predictor implies that test performances during childhood and adolescence should be considered preliminary baselines and guides for targeting domains in need of support and determining the types of interventions necessary. Due to the likelihood of catching up on some cognitive delays during adolescence and young adulthood, cognitive development should stabilise before conducting the final diagnostic assessment, typically around the mid-twenties.
In conclusion
The research project addressed the neuropsychological functioning of individuals born with CHARGE from a neuroconstructivist perspective. Restricted access to learning experiences due to sensorimotor impairment, specifically the consequences of auditory, visual, and vestibular impairments, was assumed to be the main cause of cognitive knowledge construction and development. Three clinical studies gave support to this main research hypothesis (HR) by indicating that:
(i) Individuals with atypical development are at increased risk of underestimation of intellectual ability and, thereby, obtain false positive diagnoses of intel-lectual disability because of incongruences between their sensorimotor functioning and evaluation methodology applied in health and social services (i.e., sub-hypothesis of Study I).
(ii) Executive functions of individuals with CHARGE are significantly affected by their sensorimotor functioning, negatively impacting mental flexibility while strengthening working memory (i.e., sub-hypotheses of Study II).
(iii) Realisation of the cognitive potential of individuals with CHARGE depends on the environment's ability to ensure accessibility to relevant stimuli (i.e., for the sub-hypothesis of Study III).
In line with neuroconstructivism, children born with CHARGE appear to have fewer developmental opportunities than their neurotypical peers. However, even though their developmental path emerges atypically from the embryonic stage, the environment has the power to counteract adverse genotype effects by providing neural-inducing experiences.