I have developed "tennis elbow" from lugging this book around the past four weeks, but it is worth the pain, the effort, and the aspirin. It is also worth the (relatively speaking) bargain price. Including appendixes, this book contains 894 pages of text. The entire panorama of the neural sciences is surveyed and examined, and it is comprehensive in its scope, from genomes to social behaviors. The editors explicitly state that the book is designed as "an introductory text for students of biology, behavior, and medicine," but it is hard to imagine any audience, interested in any fragment of neuroscience at any level of sophistication, that would not enjoy this book. The editors have done a masterful job of weaving together the biologic, the behavioral, and the clinical sciences into a single tapestry in which everyone from the molecular biologist to the practicing psychiatrist can find and appreciate his or

Principles of Neural Science

The study of patients to infer normal brain function has a long tradition in neurology and psychology. More recently, the motor system has been subject to quantitative and computational characterization. The pur- pose of this review is to argue that the lesion approach and theoretical motor control can mutually inform each other. Specifically, one may identify distinct motor control pro- cesses from computational models and map them onto specific deficits in patients. Here we review some of the impairments in motor control, motor learning and higher- order motor control in patients with lesions of the corti- cospinal tract, the cerebellum, parietal cortex, the basal ganglia, and the medial temporal lobe. We attempt to explain some of these impairments in terms of computa- tional ideas such as state estimation, optimization, prediction, cost, and reward. We suggest that a function of the cerebellum is system identification: to build internal models that predict sensory outcome of motor commands and correct motor commands through internal feedback. A function of the parietal cortex is state estimation: to inte- grate the predicted proprioceptive and visual outcomes with sensory feedback to form a belief about how the commands affected the states of the body and the envi- ronment. A function of basal ganglia is related to optimal control: learning costs and rewards associated with sensory states and estimating the ''cost-to-go'' during execution of a motor task. Finally, functions of the primary and the premotor cortices are related to implementing the optimal control policy by transforming beliefs about proprioceptive and visual states, respectively, into motor commands.

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A computational neuroanatomy for motor control

Work related neck and upper limb symptoms have a multi-factorial origin Possible risk factors are of a physical, psychosocial or personal origin These factors can reinforce each other and their influence can also be mediated by cultural or societal factors Initially, most research on neck and upper limb symptoms focused on work-related physical exposure Nowadays, psychosocial work characteristics are recognized as important risk factors Various models have been developed to offer frameworks for possible pathways, but their empirical support is still not conclusive In part I of this paper an overview is presented of the results of recent epidemiological studies on work related psychosocial and personal risk factors for neck and upper limb symptoms In addition, the interplay between these factors and the possible intermediate role of an individuals work style in this process is explored In contrast to previous reviews, it is now possible to base the conclusions on the effect of work related psychosocial factors on neck and upper limb symptoms on quite a few longitudinal studies These studies show that high work demands or little control at work are often related to these symptoms However, this relationship is neither very strong nor very specific Perceived stress is studied in not as many studies but more consistently related to neck and upper limb symptoms This also applies to general distress or other pain (co-morbidity) Job dissatisfaction does not contribute to neck and upper limb symptoms Too little research on personal characteristics is available to draw any conclusions It is plausible that behavioural aspects, such as work style, are of importance in the etiology of work related upper limb symptoms However, studies concerning these factors are promising but too scarce to draw conclusions Future studies should address these behavioural aspects In part II, the recent studies on the effectiveness of preventive measures for work related neck and upper limb problems are discussed Few randomised or non randomised controlled trials have been carried out to evaluate the effectiveness of individual or organisational interventions to improve work related psychosocial factors Very few have reported on the preventive effect for work related neck and upper limb symptoms Therefore, there is a great need for additional high quality trials before any conclusions on effectiveness of bio-behavioural interventions for reduction of neck and upper limb problems and return to work after these symptoms can be made From the low back pain intervention research can be learned that interventions should best be targeted to both the worker and the organisation and that interventions will only be successful when all stakeholders are involved

Epidemiology of work related neck and upper limb problems: Psychosocial and personal risk factors (Part I) and effective interventions from a bio behavioural perspective (Part II)

This article reviews the behavioral literature on the control of goal-directed aiming and presents a multiple-process model of limb control. The model builds on recent variants of Woodworth's (1899) two-component model of speed-accuracy relations in voluntary movement and incorporates ideas about dynamic online limb control based on prior expectations about the efferent and afferent consequences of a planned movement. The model considers the relationship between movement speed and accuracy, and how performers adjust their trial-to-trial aiming behavior to find a safe, but fast, zone for movement execution. The model also outlines how the energy and safety costs associated with different movement outcomes contribute to movement planning processes and the control of aiming trajectories. Our theoretical position highlights the importance of advance knowledge about the sensory information that will be available for online control and the need to develop a robust internal representation of expected sensory consequences. We outline how early practice contributes to optimizing strategic planning to avoid worst-case outcomes associated with inherent neural-motor variability. Our model considers the role of both motor development and motor learning in refining feed-forward and online control. The model reconciles procedural and representational accounts of the specificity-of-learning phenomenon. Finally, we examine the breakdown of perceptual-motor precision in several special populations (i.e., Down syndrome, Williams syndrome, autism spectrum disorder, normal aging) within the framework of a multiple-process approach to goal-directed aiming.

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Goal-Directed Aiming: Two Components but Multiple Processes.

Aging is associated with deterioration of skilled manual movement. Specifically, aging corresponds with increased reaction time, greater movement duration, segmentation of movement, increased movement variability, and reduced ability to adapt to external forces and inhibit previously learned sequences. Moreover, it is thought that decreased lateralization of neural function in older adults may point to increased neural recruitment as a compensatory response to deterioration of key frontal and intra-hemispheric networks, particularly of callosal structures. However, factors that mediate age-related motor decline are not well understood. Here we show that music training in childhood is associated with reduced age-related decline of bimanual and unimanual motor skills in a MIDI keyboard motor learning task. Compared to older adults without music training, older adults with more than a year of music training demonstrated proficient bimanual and unimanual movement, evidenced by enhanced speed and decreased movement errors. Further, this group demonstrated significantly better implicit learning in the weather prediction task, a non-motor task. The performance of older adults with music training in those tasks was comparable to young adults. Older adults, however, displayed greater verbal ability compared to young adults irrespective of a past history of music training. Our results indicate that music training early in life may reduce age-associated decline of neural motor and cognitive networks.

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Enriched childhood experiences moderate age-related motor and cognitive decline

Fifteen older adults (M = 68 years old) and 15 young adults (M = 23 years old) participated in a speed-accuracy task in which aiming movements were performed on a digitizing tablet to assess movement slowing and variability in older adults. Target-size and movement amplitude influences were analyzed separately to determine if they affected the performance of the young and older adults differently. When target size was increased, older adults did not increase the relative distance traveled in the primary submovement. When movement amplitude was increased, older adults did not scale movement velocities to the same magnitude as young adults did. Both the inability to scale velocity and the inability to increase the relative distance traveled in the primary submovement contribute to slower, more variable movements observed in older adults depending on task parameters. Thus, these data reveal that manipulation of target size and movement amplitude yield two distinct factors that contribute to slowness of movement in older adults.

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Age-Related Kinematic Differences as Influenced by Task Difficulty, Target Size, and Movement Amplitude

Background Work-related Upper Extremity Disorders (WRUEDs) are conceived of as a multifactorial syndrome caused by the effects of excessive repetitive motions, sustained static postures, and muscular stiffness. Our aim is to test an etiological model derived from a theory by Van Galen and Van Huygevoort [2000] Biol Psychol 51:151–171. The theory holds that physical, emotional, and psychosocial stressors enhance muscular stiffness as a compensatory filtering of impoverished signal-to-noise ratios in the motor system. High individual levels of arousal, as measured by Spielberger et al. [1970], State and Trait Anxiety Test would further enhance a subject’s predisposition to react with stiffness responses in conditions of stress. Methods Ten participants with a high- and 10 with a low trait-anxiety score performed a computer task involving series of fast but well-dosed accelerations of the forearm along the surface of a digitizer. To induce cognitive stress a tone had to be remembered simultaneously with the aiming task. Pen-tip displacements and surface electromyographic (EMG) signals were recorded from four forearm muscles. Results Memory load did not affect error rates but produced shorter reaction times and prolonged movement times. EMG data show that under stress overall levels of neuromotor activation were enhanced. High-anxious participants exhibited higher cocontraction levels than low-anxious participants. Conclusions The findings support the view that stress and muscular tension are closely related and may provide a clue to the origin of WRUEDs. Am. J. Ind. Med. 41:406–419, 2002. 2002 Wiley-Liss, Inc.

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Forearm EMG response activity during motor performance in individuals prone to increased stress reactivity.

Parkinsonian Patients Reduce Their Stroke Size with Increased Processing Demands

To address the hypothesis that Parkinson's disease (PD) patients have deficits in controlling acceleration, a drawing task was used in which target size, frequency, and weight of pen were manipulated. In accordance with previous results, it was found that, relative to controls, PD patients produced movements at the required frequency, but moved significantly slower, produced less acceleration, and drew smaller-than-required stroke sizes. This resulted in smaller-than-required movement amplitudes, suggesting that hypometria and bradykinesia in drawing and/or handwriting are related. Patients were found to perform similarly to controls when the target size was 1 cm. However, their performance became more dissimilar at greater stroke lengths. In addition to the aforementioned effects it was found that movement amplitude error was less when the pen was 20 times heavier than the normal pen and that the increased load may dampen abnormal limb-stiffness characteristics induced by PD.

Arend W.A. Van Gemmert

Papers

Age-Related Kinematic Differences as Influenced by Task Difficulty, Target Size, and Movement Amplitude

Forearm EMG response activity during motor performance in individuals prone to increased stress reactivity.

Parkinsonian Patients Reduce Their Stroke Size with Increased Processing Demands

Hypometria and bradykinesia during drawing movements in individuals with Parkinson’s disease

Movement structure in young and elderly adults during goal-directed movements of the left and right arm.