Consensus paper: the cerebellum's role in movement and cognition.

While the cerebellum's role in motor function is well recognized, the nature of its concurrent role in cognitive function remains considerably less clear. The current consensus paper gathers diverse views on a variety of important roles played by the cerebellum across a range of cognitive and emotional functions. This paper considers the cerebellum in relation to neurocognitive development, language function, working memory, executive function, and the development of cerebellar internal control models and reflects upon some of the ways in which better understanding the cerebellum's status as a "supervised learning machine" can enrich our ability to understand human function and adaptation. As all contributors agree that the cerebellum plays a role in cognition, there is also an agreement that this conclusion remains highly inferential. Many conclusions about the role of the cerebellum in cognition originate from applying known information about cerebellar contributions to the coordination and quality of movement. These inferences are based on the uniformity of the cerebellum's compositional infrastructure and its apparent modular organization. There is considerable support for this view, based upon observations of patients with pathology within the cerebellum.

From movement to thought: executive function, embodied cognition, and the cerebellum.

This paper posits that the brain evolved for the control of action rather than for the development of cognition per se. We note that the terms commonly used to describe brain-behavior relationships define, and in many ways limit, how we conceptualize and investigate them and may therefore constrain the questions we ask and the utility of the "answers" we generate. Many constructs are so nonspecific and over-inclusive as to be scientifically meaningless. "Executive function" is one such term in common usage. As the construct is increasingly focal in neuroscience research, defining it clearly is critical. We propose a definition that places executive function within a model of continuous sensorimotor interaction with the environment. We posit that control of behavior is the essence of "executive function," and we explore the evolutionary advantage conferred by being able to anticipate and control behavior with both implicit and explicit mechanisms. We focus on the cerebellum's critical role in these control processes. We then hypothesize about the ways in which procedural (skill) learning contributes to the acquisition of declarative (semantic) knowledge. We hypothesize how these systems might interact in the process of grounding knowledge in sensorimotor anticipation, thereby directly linking movement to thought and "embodied cognition." We close with a discussion of ways in which the cerebellum instructs frontal systems how to think ahead by providing anticipatory control mechanisms, and we briefly review this model's potential applications.

Sensory integration, sensory processing, and sensory modulation disorders: putative functional neuroanatomic underpinnings.

This paper examines conditions that have variously been called sensory integration disorder, sensory processing disorder, and sensory modulation disorder (SID/SPD/SMD). As these conditions lack readily and consistently agreed-upon operational definitions, there has been confusion as to how these disorders are conceptualized. Rather than addressing various diagnostic controversies, we will instead focus upon explaining the symptoms that are believed to characterize these disorders. First, to clarify the overall context within which to view symptoms, we summarize a paradigm of adaptation characterized by continuous sensorimotor interaction with the environment. Next, we review a dual-tiered, integrated model of brain function in order to establish neuroanatomic underpinnings with which to conceptualize the symptom presentations. Generally accepted functions of the neocortex, basal ganglia, and cerebellum are described to illustrate how interactions between these brain regions generate both adaptive and pathological symptoms and behaviors. We then examine the symptoms of SID/SPD/SMD within this interactive model and in relation to their impact upon the development of inhibitory control, working memory, academic skill development, and behavioral automation. We present likely etiologies for these symptoms, not only as they drive neurodevelopmental pathologies but also as they can be understood as variations in the development of neural networks.

Adaptation, expertise, and giftedness: towards an understanding of cortical, subcortical, and cerebellar network contributions.

Current cortico-centric models of cognition lack a cohesive neuroanatomic framework that sufficiently considers overlapping levels of function, from "pathological" through "normal" to "gifted" or exceptional ability. While most cognitive theories presume an evolutionary context, few actively consider the process of adaptation, including concepts of neurodevelopment. Further, the frequent co-occurrence of "gifted" and "pathological" function is difficult to explain from a cortico-centric point of view. This comprehensive review paper proposes a framework that includes the brain's vertical organization and considers "giftedness" from an evolutionary and neurodevelopmental vantage point. We begin by discussing the current cortico-centric model of cognition and its relationship to intelligence. We then review an integrated, dual-tiered model of cognition that better explains the process of adaptation by simultaneously allowing for both stimulus-based processing and higher-order cognitive control. We consider the role of the basal ganglia within this model, particularly in relation to reward circuitry and instrumental learning. We review the important role of white matter tracts in relation to speed of adaptation and development of behavioral mastery. We examine the cerebellum's critical role in behavioral refinement and in cognitive and behavioral automation, particularly in relation to expertise and giftedness. We conclude this integrated model of brain function by considering the savant syndrome, which we believe is best understood within the context of a dual-tiered model of cognition that allows for automaticity in adaptation as well as higher-order executive control.

Attention and other constructs: evolution or revolution?

This article provides a review of the construct of attention from a non-traditional standpoint. Attention is conceptualized by focusing on the categorical concept of the diagnosis of attention-deficit hyperactivity disorder, large-scale brain network models of functional neuroanatomy, and implications for understanding lateralized hemispheric brain organization. Cortical systems are multifunctional, with certain degrees of specialization, but no cortical region or network supports only one, specific, isolated cognitive process, such as attention. Future implications for clinical practice must focus on connectivity patterns rather than the idea of "domains" or "constructs" when considering attention and other cognitive processes. This has significant implications for the future of neuropsychological assessment and intervention.

The neuropsychology of attention: revisiting the "Mirsky model".

Nearly 25 years ago, Mirsky and colleagues proposed a multiple-component model of attention. It was proposed that attention was characterized by several distinct elements that were organized into a system. A putative neuroanatomical substrate of this model of attention was proposed. This functional anatomy was primarily based upon inferences derived from brain lesion studies. Mirsky and colleagues developed a systematic clinical evaluation of this model by applying a group of neuropsychological tests. Since the introduction of what has been commonly referred to as the "Mirsky model," significant advances have been made in our understanding of brain-behavior relationships. This article applies current neuroscientific principles to "update" our understanding of attention and the "Mirsky model." We also demonstrate how the interpretation of neuropsychological tests can be modified according to principles of large-scale brain systems and patterns of brain network functional connectivity.

Structure and function of large-scale brain systems.

This article introduces the functional neuroanatomy of large-scale brain systems. Both the structure and functions of these brain networks are presented. All human behavior is the result of interactions within and between these brain systems. This system of brain function completely changes our understanding of how cognition and behavior are organized within the brain, replacing the traditional lesion model. Understanding behavior within the context of brain network interactions has profound implications for modifying abstract constructs such as attention, learning, and memory. These constructs also must be understood within the framework of a paradigm shift, which emphasizes ongoing interactions within a dynamically changing environment.

The small-world organization of large-scale brain systems and relationships with subcortical structures.

Brain structure and function is characterized by large-scale brain systems. However, each system has its own "small-world" organization, with sub-regions, or "hubs," that have varying degrees of specialization for certain cognitive and behavioral processes. This article describes this small-world organization, and the concepts of functional specialization and functional integration are defined and explained through practical examples. We also describe the development of large-scale brain systems and this small-world organization as a sensitive, protracted process, vulnerable to a variety of influences that generate neurodevelopmental disorders.

Large-scale brain systems and subcortical relationships: the vertically organized brain.

This article reviews the vertical organization of the brain. The cortico-basal ganglia and the cerebro-cerebellar circuitry systems are described as fundamental to cognitive and behavioral control. The basal ganglia anticipate and guide implicitly learned behaviors on the basis of experienced reward outcomes. The cerebellar-cortical network anticipates sensorimotor outcomes, allowing behaviors to be adapted across changing settings and across contexts. These vertically organized systems, operating together, represent the underpinning of cognitive control. The medial temporal lobe system, and its development, is also reviewed in order to better understand how brain systems interact for both implicit and explicit cognitive control.

Large-scale brain systems and subcortical relationships: practical applications.

This article describes an interactive paradigm for understanding brain functioning. This model requires both explicit and implicit learning processes. This paradigm is illustrated through the interpretation of practical examples of behavior. Applications of current neuropsychological tests are presented within this interactive paradigm. The development of new neuropsychological tests is presented, as derived from experimental test paradigms that evaluate implicit learning processes.

From movement to thought: the development of executive function.

This article presents a very simple definition of executive functioning (EF). Although EF is traditionally understood as a cognitive function dependent upon top-down cortical control, we challenge this model. We propose that the functional architecture of the brain evolved to meet the needs of interactive behavior and that cognition develops to control the motor system, which is of paramount importance in adaptation, essentially a manifestation of EF. We propose that traditional models of cognition are incomplete characterizations of EF and that procedural learning and "automatic" behaviors are the most basic, bottom-up functions that support all EF. We propose that motor development in children demonstrates how all knowledge is grounded in sensorimotor interaction and how interactive behavior generates both procedural and declarative knowledge, which later interact to generate EF. This model emphasizes the critical importance of motor behavior in children and stresses the importance of the pediatric motor examination in understanding the development of EF. This model also has implications for why traditional tests of EF have little predictive validity in both children and adults.

Hypotonia, jaundice, and Chiari malformations: relationships to executive functions.

This article postulates that movement and action control are the underpinning of executive functioning. We selectively examine brain regions that have traditionally been almost exclusively understood as critical to the control and expression of movement-namely, the basal ganglia and the cerebellum. We first describe the relationship between movement and cognition. This is followed by a review of common developmental disorders that are known to exhibit abnormal executive functions and movement anomalies. Against that background, we examine hypotonia, neonatal jaundice, and Chiari I malformation, and we demonstrate why these are "at-risk" factors for neurodevelopmental disorders that can feature both motor control and executive function abnormalities. Our goal is to prepare the clinical neuropsychologist for gathering information about these features of a child's birth and developmental histories, while using this as a framework for interpreting test results and applying test data in a useful, practical way to guide descriptive diagnosis and treatment.

Hyperbilirubinemia: subcortical mechanisms of cognitive and behavioral dysfunction.

Although development of the full syndrome of kernicterus is relatively rare, neonatal jaundice continues to occur frequently. Controversy remains concerning whether or not infants with moderate elevations in bilirubin are at risk for neurodevelopmental disorders in later childhood. Sites of brain pathology associated with bilirubin neurotoxicity are identified and well established. Based on these regions of brain involvement, we apply neuroscientific principles of brain-behavior relationships to predict types of cognitive features that may accompany hyperbilirubinemia. We address a range of neurodevelopmental abnormalities that can arise as a function of elevated neonatal bilirubin levels affecting these brain regions, even in the absence of full kernicterus syndrome. Moreover, we explain the neuropathologic mechanisms that would drive these abnormalities. We thus attempt to establish a blueprint for future investigations of these conditions, to improve neurodevelopmental outcomes.

Requiem for a diagnosis: attention-deficit hyperactivity disorder.

This editorial discusses the diagnosis of ADHD from behavioral and neuropsychological viewpoints. The DSM and clinical neuropsychology offer two completely different nomenclatures while brain-behavior relationships do not easily "map" on to the symptom picture of ADHD. Neuropsychological evaluation offers specificity in identifying and treating individual ADHD presentations, avoiding the heterogeneity inherent in the DSM diagnosis of ADHD.

ADHD and sensory processing disorders: placing the diagnostic issues in context.

Attention-deficit hyperactivity disorder (ADHD) and sensory processing disorders are behaviorally defined conditions that often co-occur, while both diagnoses have been controversial in part due to the constraints of categorical behavioral diagnosis. However, neuroanatomic studies using neuropsychological tests as "probes" have clearly demonstrated that the various symptoms of ADHD are the result of abnormalities in large-scale brain networks. Sensory processing disorders have not yet been grounded within a neuroanatomical substrate. This article reviews sensory processing disorder as a categorically based diagnosis. It discusses certain possible neuroanatomical relationships between the symptoms of ADHD and sensory processing disorders, and suggests that the symptoms of sensory processing disorders be studied within the dimensional framework of research domain criteria.

Neuropsychological assessment and the paradox of ADHD.

Attention-deficit hyperactivity disorder (ADHD) is a behaviorally defined diagnosis. Despite the fact that neuropsychological tests have typically been used successfully to investigate the functional neuroanatomy of ADHD in neuroimaging research paradigms, these tests have been of surprisingly limited utility in the clinical diagnosis of the disorder. This article examines this paradox by reviewing the characteristics of the Diagnostic and Statistical Manual of Mental Disorders diagnosis versus neuropsychological nomenclature, by reviewing the assumptions about etiologies for ADHD and by demonstrating how an emerging dimensional approach to diagnostic assessment can be combined with large-scale brain network studies to enhance the role of neuropsychological evaluation within clinical settings. This selective topical review is intended to arm practicing neuropsychologists with knowledge of new ideas, theories, and methods related to the causes of ADHD to prepare them for meaningful advances in understanding and assessing the disorder that are possible during the next decade.