Developmental Cognitive Neuropsychology: Challenges and Promises

Article excerpt

This special issue of Cognition, Brain, Behavior is concerned with the developmental neuropsychological approach viewed through multiple lens. The field is, by its very essence, interdisciplinary; it exists at the interplay of multiple influences from traditional neuropsychology, cognitive psychology, developmental psychology and cognitive neuroscience.

The fundamental aims of developmental neuropsychology have changed across time; while initially it was claimed that - as in the case of adult cognitive neuropsychology - the ultimate aim was to construct theoretical models of cognitive domains, against which all childhood cases of disorders of those domains could be explained (Temple, 1997), it is nowadays clear that the purpose is hardly reachable, and maybe even unrealistic. The multilevel analysis of the development of atypical groups does not support the perspective of a normal brain with whole circuits intact or impaired, as in the adult neuropsychological model; there is a different dynamic of brain development at multiple levels (genetic, metabolic, functional), throughout embryogenesis and postnatal development (Karmiloff-Smith, 2007).

Contemporary non-invasive neuroimaging methods have provided developmental scientists with the opportunity to track "on-line" neural underpinnings of task-solving processes (see Casey et al., 2006, for a review); however, the tasks that can be examined through these lenses are simplified, and to a great extent, non-ecological. In addition, the investigation of atypical brain phenotypes is extremely limited due to difficulties in interpreting the neuroimaging results for tasks that the children have difficulties in resolving (Filipek, 1999; Humphreys & Price, 2001). Only by combining the results of neuroimaging investigations with the results from studies in developmental cognitive neuropsychology will we be able to map the behavioral level onto contrasting and complementary patterns of brain morphology and generate new hypotheses about the brain systems responsible for those atypical patterns of behavior (Bates & Appelbaum, 1994).

Before analyzing the contributions of the papers in this special issue to this generous aim, we have to mention that there are distinct types of designs involved in neuropsychological assessment according to the format and the logic of the tests being used (Fennell, 2000). First of all, the researcher could rely on a fixed battery approach, administering the same set of standardized tests to each child, regardless of the diagnostic question. The developmental neuropsychological batteries are empirically derived, sometimes from adult versions of the tests with items altered, deleted or eliminated, to make them more age appropriate for children. The emphasis is in this case on the quantitative differentiation of patient groups from normal children, without respect to many qualitative aspects of this difference. A second approach would be the flexible battery approach, which utilizes a core battery of standardized tests that are administered, along with additional tests that are selected to address specific referral questions. Finally, the patient-centered approach allows the examiner to select tests to be employed based on both the referral question and the child's performance on a given task, which provides an individualized portrait of the child's cognitive-behavioral status. At this point, we would add to Fennell's (2000) classification a profile-centered approach, which is either exploratory or confirmatory in nature, and which employs refined experimental tasks evaluating critical abilities consider to be impaired or spared in children with a certain diagnosis (Petra & Benga, 2004). The resulting evaluation leads to the identification of cognitive-behavioral phenotypes, namely "the heightened probability of a behavior or cognitive feature to characterize a particular syndrome" (Dykens, 2000), with important implications both for the intervention plan in the case of children with that diagnosis and for theoretical models regarding patterns of brain-behavior relationships noticed in these profiles.

With these specifications in mind, we can relate to the distinct approaches of the articles in this special issue. The first two papers are good illustrations of the profile-centered approach. Building on the solid knowledge of particularities in the case of Williams syndrome or autism disorder, they advance new hypothesis to clarify aspects of each cognitive-behavioral (and social) phenotype. Tager-Flusberg, Plesa-Skwerer, Schofield, Verbalis and Simons (this issue) investigate change detection in adolescents and adults with Williams syndrome, hypothesizing that they would be more sensitive to changes in people in social scenes compared to matched participants with learning or intellectual disabilities. Indeed, participants with Williams syndrome were more likely to identify changes related to social elements to describe the emotional states of the actors, indicating that their attentional focus was on the people rather than on the nonsocial areas of the visual scene. This conclusion provided support to idea that the mechanisms characterizing a certain atypical phenotype may be more related to motivational, arousal and attentional patterns than to higher level cognitive systems, an idea stressed by dr. Tager-Flusberg in her interview for this special issue. From a different perspective, Vlachos, Tsiftzi, and Agapitou (this issue) aim to find additional support for an important theory in autism research, emphasizing the role of cerebellar dysfunction; they try to pinpoint correlates of this dysfunction through the use of motor tasks that represent a putative index of cerebellar functioning impairments. They propose such motor tasks to be included in routine assessment and diagnosis of autistic disorders throughout the childhood years.

While the focus of the abovementioned papers was on neurodevelopmental disorders, the following two papers approach the neurocognitive, sociocognitive and language correlates of neurological impairment as a result of pre/perinatal brain lesions or of temporal/frontal lobe epilepsy. Two aspects should be mentioned with regard to these studies. First of all, research has revealed the improbability of identifying clear-cut neurocognitive profiles associate either with distinct early brain lesions (Stiles, Reilly, Paul, & Moses, 2005), or different types of childhood epilepsy (Jokeit & Schacher, 2005). Second, the papers illustrate a tedious debate in neuropsychology regarding the informative value of group studies versus single case studies in investigating the correlates of brain damage. "Radical" neuropsychologists claimed that we should not expect or require replications in cognitive neuropsychology, because it is quite unlikely to find patients with identical lesions and without confounding external conditions (Caramazza, 1986). On the other hand, the call has been strong for developmental neuropsychology to focus on group studies: "the answer is not to restrict attention to the study of individual cases, but, rather, to identify reliable clusters of deficits; only by studying groups of individuals can we begin to disentangle what is systematic signal and what is noise from the complex patterns of impairment" (Bishop, 1997). The paper by Simlesa, Ivsac, and Ljubesic (this issue) choses to pursue a group approach with both standardized and experimental tasks; they identify delays in the brain-lesioned group in general cognitive abilities, executive functions, socio-cognitive abilities and language. However, the authors acknowledge that due to the lack of neuroimaging information and the limited sample size, it is difficult to draw any conclusion regarding the specific relationships between particular brain lesions and socio-cognitive and linguistic functioning in these children. Palade and Benga (this issue) use the flexible neuropsychological approach provided by the CANTAB battery and identify different profiles of impairment in temporal versus frontal lobe epilepsy as revealed by two case studies; an important asset of the paper is the use of repeated evaluations, that allow to monitor both the dynamics of neural dysfunction related to seizure disorder, and the results of the medical treatment that the children undergo.

With a similar methodology (the CANTAB battery), but focusing on a particular test measuring attentional flexibility (the Intra/Extradimensional Set Shift task), lincas, Dragos, Ionescu, and Benga (this issue) relate performance and solving strategy on this task to anxiety symptoms and gender individual differences in preschool children. The paper illustrates a common trend in modern psychopathological research: the identification of neurobiological underpinnings of several internalizing and externalizing disorders that has inevitably led to a need to pinpoint the neuropsychological correlates of these specific neurobiological dysfunctions (Brunnekreef et al., 2007). The paper by Porumb (this issue) applies a neuropsychological approach, this time to an externalizing disorder, Attention Deficit Hyperactivity Disorder. The utility of a mixed battery approach (Test of Variables of Attention: T.O.V.A., and NEPSY: A Developmental Neuropsychological Assessment is revealed through the analysis of a case study; the conclusion is that by combining information from multiple assessment sources, one can increase the validity of the inferences related to a specific diagnostic and evaluation output.

The final two papers both relate to the flexible-battery approach provided by NEPSY: A Developmental Neuropsychological Assessment, but from different perspectives. In both papers, the instrument is adapted for use in a different cultural context: for the Romanian population (Visu-Petra, Benga, & Miclea) and for the South African population (Dalen, Jellestad, & Kamaloodien). The instrument is used for evaluating the developmental pathways of executive functioning within a large age interval: 5 to 12 years; the results reveal a distinct, earlier maturational timetable of inhibitory functions as compared to more complex, high-order abilities like planning or verbal/design fluency (Visu-Petra, Benga, & Miclea, this issue). The paper by Dalen, Jellestad, and Kamaloodien (this issue) deals with the important issue of ethical considerations involved in adapting NEPSY-II to Afrikaans; the authors relate general ethical principles of test adaptation and administration to the particular realities of the South African context, in order to prevent misuse and segregation based on test results. Both papers have an important implicit message: the informative value of the neuropsychology of typical development, as a source of inferences for brain-behavior relationships in developmental psychology and for designing optimization strategies for the improvement of "typical" performance (Segalowitz & Hiscock, 1992).

All the papers in this special issue clearly reflect the persistent challenges that nowadays' developmental cognitive neuropsychology has to face: reliance on rare atypical populations, difficulties in combining its results with neuroimaging or adult population findings, the unresolved group versus single case debate, the particular difficulties associated with the standardized or the experimental, profilecentered approach, and many others. However, they also reveal some of the generous promises of a developmental neuropsychological approach to both typical and atypical trajectories, among which: the possibility to investigate ecological abilities relevant for the child's everyday functioning, the heuristic value for brainbehavior mappings when combined with neuroimaging data, and last, but definitely not least, the direct link to intervention programs in the case of developmental disorders.

The Editors

ACKNOWLEDGMENTS

The editors appreciate dr. Eva Kallay's help during the edit-proofing process and the contribution of Lavinia Cheie and Daniela Teodora Onca to the final formatting of the manuscripts.

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