Foreword

This special issue includes a group of short articles based on the lectures presented at a symposium in Paris in November 2013, as the conclusion of the work of an international scientific group and a pilot research study, both around Perception, Action, Cognition, Environment (PACE) in cerebral palsy (CP). La Fondation Motrice, a French organization comprising parents and experts, devoted to research into CP, promoted the scientific group and the pilot study. Alain Chatelin and Lucie Hertz-Pannier describe in more detail in the other part of this foreword the history of the project, its main actors, and initiatives. The main concepts of PACE include and expand the updated definition (and classification) that describes CP ‘as a group of disorders of the development of movement and posture. . . often accompanied by disturbances of sensation, cognition, communication, perception, and/or behaviour, and/or by a seizure disorder.’ For the first time, the association with ‘not primarily motor’ disorders such as cognition, communication, perception, and others has been mentioned in the definition, pointing out that these ‘accompanying’ disorders are strongly linked to motor disorders and might be the major cause of activity limitation for people with CP. The recent excellent book edited by Dan et al. acknowledges this concept and largely covers cognition and all the other non-motor aspects of CP. These disorders are reported as very frequent in people with CP (see Novak et al.). However, not having homogeneous definitions, they lack dedicated and specific assessment tools, and precise data on the total incidence and distribution in the subtypes of CP (for visual perceptual disorders see Ego et al., this issue). People with CP were interviewed by La Fondation Motrice, with the aim of identifying the most relevant topics to be selected for the research supported by the association. Perception and cognition were identified as key factors that account for their disabilities making their study worthwhile. The opinion of stakeholders has a correspondence with new models of motor control and learning in typical development, and in various neurological disorders, based on strong interaction with cognitive, perceptual, and emotional functions. The PACE approach indicates that perception, action, cognition, and interaction with the environment should not be seen as separate ‘functions’, to be isolated and analysed in uni-modular, poorly ecological experimental conditions. Although such a traditional way of focusing on the possible dissociations of each function from the others has proved effective in many respects, it does not address some key questions emerging from clinical and daily-life settings. In the past decade, new discoveries and models in neuroscience have led most researchers to consider these aspects of brain functioning as deeply blended and to some extent co-emerging throughout development. A paradigm shift from isolated, modular functions to functional integration has taken place. This, in turn, now challenges our mission as basic and clinical researchers, health professionals, and care-givers, in that we are confronted with a complex, multi-faceted, and highly interconnected brain, whose disturbances cannot be fully understood or treated, except in a complex, multi-faceted, and integrated way. New research protocols are thus needed, acting in an integrative perspective, in addition to more traditional research addressing specifically isolated functions independently from one another. The papers included in this issue highlight some of the theoretical background of the PACE approach as well as reviews of its translation into new diagnostic and rehabilitation studies, for CP and other neurodevelopmental disorders. In this issue, Alain Berthoz and M Zaoui report examples of brain perceptual and cognitive systems, such as spatial memory and executive functions, that are involved in children’s ‘navigation’ in their environment to fulfil their adaptive needs. Children with CP may suffer several disorders in these abilities, as hypothesized in the paper, with possible pathophysiological profiles that may potentially lead to tailored remediation approaches. To test these and other challenging hypotheses, we need to develop tools to explore these cognitive functions in action. Some of these tests are described in this issue, such as the ‘magic carpet’, a test derived from the Corsi Block-Tapping Task, to analyse spatial memory and representations during navigation, whereas available tests to investigate manual action in infancy are reviewed in another paper (Krumlinde-Sundholm et al.). As indicated by Dan et al., although the main focus of the PACE research group has been on CP, this approach can also be useful for other disorders that, at the symptom level, seem to share similar behavioural and diagnostic criteria. In the Diagnostic and Statistical Manual of Mental Disorders, 5th edition a new cluster of neurodevelopmental disorders is proposed, which includes six categories: intellectual developmental disorders, communication disorders, autism spectrum disorders, attention-deficit–hyperactivity disorder (ADHD), learning disorders, and motor disorders. This new cluster has as several main features to highlight the characteristics of deficits/delays in ‘maturationally-influenced’ psychological features, cognitive impairment, genetic influences, and overlap among the neurodevelopmental disorders.