Objective: Parkinson’s disease (PD) is a progressive neurological disorder characterised by a large number of motor and non-motor features that can impact on function to a variable degree. This review describes the clinical characteristics of PD with emphasis on those features that differentiate the disease from other parkinsonian disorders. Methods: A MedLine search was performed to identify studies that assess the clinical characteristics of PD. Search terms included “Parkinson’s disease”, “diagnosis” and “signs and symptoms”. Results: Because there is no definitive test for the diagnosis of PD, the disease must be diagnosed based on clinical criteria. Rest tremor, bradykinesia, rigidity and loss of postural reflexes are generally considered the cardinal signs of PD. The presence and specific presentation of these features are used to differentiate PD from related parkinsonian disorders. Other clinical features include secondary motor symptoms (eg, hypomimia, dysarthria, dysphagia, sialorrhoea, micrographia, shuffling gait, festination, freezing, dystonia, glabellar reflexes), non-motor symptoms (eg, autonomic dysfunction, cognitive/neurobehavioral abnormalities, sleep disorders and sensory abnormalities such as anosmia, paresthesias and pain). Absence of rest tremor, early occurrence of gait difficulty, postural instability, dementia, hallucinations, and the presence of dysautonomia, ophthalmoparesis, ataxia and other atypical features, coupled with poor or no response to levodopa, suggest diagnoses other than PD. Conclusions: A thorough understanding of the broad spectrum of clinical manifestations of PD is essential to the proper diagnosis of the disease. Genetic mutations or variants, neuroimaging abnormalities and other tests are potential biomarkers that may improve diagnosis and allow the identification of persons at risk.

https://jnnp.bmj.com/content/jnnp/79/4/368.full.pdf

Parkinson’s disease: clinical features and diagnosis

Preparing words in speech production is normally a fast and accurate process. We generate them two or three per second in fluent conversation; and overtly naming a clear picture of an object can easily be initiated within 600 msec after picture onset. The underlying process, however, is exceedingly complex. The theory reviewed in this target article analyzes this process as staged and feed-forward. After a first stage of conceptual preparation, word generation proceeds through lexical selection, morphological and phonological encoding, phonetic encoding, and articulation itself. In addition, the speaker exerts some degree of output control, by monitoring of self-produced internal and overt speech. The core of the theory, ranging from lexical selection to the initiation of phonetic encoding, is captured in a computational model, called WEAVER++. Both the theory and the computational model have been developed in interaction with reaction time experiments, particularly in picture naming or related word production paradigms, with the aim of accounting for the real-time processing in normal word production. A comprehensive review of theory, model, and experiments is presented. The model can handle some of the main observations in the domain of speech errors (the major empirical domain for most other theories of lexical access), and the theory opens new ways of approaching the cerebral organization of speech production by way of high-temporal-resolution imaging.

/pdf/a-theory-of-lexical-access-in-speech-production-4daokag4lw.pdf

A theory of lexical access in speech production.

1980 Preface * 1999 Preface * 1999 Acknowledgements * Introduction * 1 Circular Logic * 2 Phase Singularities (Screwy Results of Circular Logic) * 3 The Rules of the Ring * 4 Ring Populations * 5 Getting Off the Ring * 6 Attracting Cycles and Isochrons * 7 Measuring the Trajectories of a Circadian Clock * 8 Populations of Attractor Cycle Oscillators * 9 Excitable Kinetics and Excitable Media * 10 The Varieties of Phaseless Experience: In Which the Geometrical Orderliness of Rhythmic Organization Breaks Down in Diverse Ways * 11 The Firefly Machine 12 Energy Metabolism in Cells * 13 The Malonic Acid Reagent ('Sodium Geometrate') * 14 Electrical Rhythmicity and Excitability in Cell Membranes * 15 The Aggregation of Slime Mold Amoebae * 16 Numerical Organizing Centers * 17 Electrical Singular Filaments in the Heart Wall * 18 Pattern Formation in the Fungi * 19 Circadian Rhythms in General * 20 The Circadian Clocks of Insect Eclosion * 21 The Flower of Kalanchoe * 22 The Cell Mitotic Cycle * 23 The Female Cycle * References * Index of Names * Index of Subjects

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/596B270197FE27DE5FABB598B6210622/S0025557200150892a.pdf/div-class-title-span-class-italic-the-geometry-of-biological-time-span-by-a-t-winfree-pp-544-dm68-corrected-second-printing-1990-isbn-3-540-52528-9-springer-div.pdf

The geometry of biological time , by A. T. Winfree. Pp 544. DM68. Corrected Second Printing 1990. ISBN 3-540-52528-9 (Springer)

A central problem in motor control is understanding how the many biomechanical degrees of freedom are coordinated to achieve a common goal. An especially puzzling aspect of coordination is that behavioral goals are achieved reliably and repeatedly with movements rarely reproducible in their detail. Existing theoretical frameworks emphasize either goal achievement or the richness of motor variability, but fail to reconcile the two. Here we propose an alternative theory based on stochastic optimal feedback control. We show that the optimal strategy in the face of uncertainty is to allow variability in redundant (task-irrelevant) dimensions. This strategy does not enforce a desired trajectory, but uses feedback more intelligently, correcting only those deviations that interfere with task goals. From this framework, task-constrained variability, goal-directed corrections, motor synergies, controlled parameters, simplifying rules and discrete coordination modes emerge naturally. We present experimental results from a range of motor tasks to support this theory.

/pdf/optimal-feedback-control-as-a-theory-of-motor-coordination-jh26vkl3kk.pdf

Optimal feedback control as a theory of motor coordination.

The generation of words in speech involves a number of processing stages. There is, first, a stage of conceptual preparation; this is followed by stages of lexical selection, phonological encoding, phonetic encoding and articulation. In addition, the speaker monitors the output and, if necessary, self-corrects. Major parts of the theory have been computer modelled. The paper concentrates on experimental reaction time evidence in support of the theory.

/pdf/a-theory-of-lexical-access-in-speech-production-56yj14t9eb.pdf

A theory of lexical access in speech production

1. The movement sensitivity of dorsal skin mechanoreceptors in the human hand was studied by the use of single afferent recording techniques. 2. Units were classified as slowly (SA) and fast adapting (FA) and further characterized by thresholds to vertical indentation and by receptive-field sizes. Whereas SA units were evenly distributed within the supply area of the superficial branch of the radial nerve. FA units were usually situated near joints. 3. The proportion of different receptor types (32% SAI, 32% SAII, 28% FAI, 8% FAII; n = 107) compared favorably with previous electrophysiological and anatomic data, arguing for minimal sampling bias. The majority of the skin mechanoreceptive units were SA, largely due to a relative scarcity of FAII [Pacinian corpuscles (PC)] units. 4. A large majority (92%) of the afferents responded to active hand or finger movements. Responses in all unit types were consistent with observed movement-induced deformations of their receptive fields. 5. FAI units responded bidirectionally, albeit usually with somewhat higher discharge frequencies for finger flexion, which in most cases were associated with skin stretch. FAI units showed meager responses to remote stimuli, typically responding to one or, at the most, two adjacent joints. 6. SA units typically showed simple directional responses to joint movements with an increased discharge during flexion and a reduced discharge during extension. Joint movement that influenced the skin within the receptive field of SA units elicited graded responses even if the field, as assessed by perpendicular indentations, was minute. This finding suggests that definition of cutaneous receptive fields by classical perpendicular indentations may be inappropriate for the receptors in the hairy, nonglabrous skin. 7. The interpretation of the data from these recordings suggests that cutaneous mechanoreceptors in the dorsal skin can provide the CNS with detailed kinematic information, at least for movements of the hand.

Finger movement responses of cutaneous mechanoreceptors in the dorsal skin of the human hand

The contribution of ascending afferents to the control of speech movement was evaluated by applying unanticipated loads to the lower lip during the generation of combined upper lip-lower lip speech gestures. To eliminate potential contamination due to anticipation or adaptation, loads were applied randomly on only 10-15% of the trials. Physical characteristics of the perturbations were within the normal range of forces and movements involved in natural lip actions for speech. Compensatory responses in multiple facial muscles and lip movements were observed the first time a load was introduced, and achievement of the multimovement speech goals was never disrupted by these perturbations. Muscle responses were seen in the lower lip muscles, implicating corrective, feedback processes. Additionally, compensatory responses to these lower lip loads were also observed in the independently controlled muscles of the upper lip, reflecting the parallel operation of open-loop, sensorimotor mechanisms. Compensatory responses from both the upper and lower lip muscles were observed with small (1 mm) as well as large (15 mm) perturbations. The latencies of these compensatory responses were not discernible by conventional ensemble averaging. Moreover, responses at latencies of lower brain stem-mediated reflexes (i.e., 10-18 ms) were not apparent with inspection of individual records. Response latencies were determined on individual loaded trials through the use of a computer algorithm that took into account the variability of electromyograms (EMG) among the control trials. These latency measures confirmed the absence of brain stem-mediated responses and yielded response latencies that ranged from 22 to 75 ms. Response latencies appeared to be influenced by the time relation between load onset and the initiation of muscle activation. Examination of muscle activity changes for individual loaded trials revealed complementary variations in the magnitude of responses among multiple muscles contributing to a movement compensation. These observations may have implications for limb movement control if multimovement speech gestures are considered analogous to a limb action requiring coordinated movements around multiple joints. In this context, these speech motor control data might be interpreted to suggest that for complex movements, both corrective feedback and open-loop predictive processes are operating, with the latter involved in the control of coordination among multiple movement subcomponents.

Control of complex motor gestures: orofacial muscle responses to load perturbations of lip during speech.

Afferent contributions to the motor control of speech were evaluated by applying unanticipated loads to the lower lip during the combined upper lip-lower lip gesture associated with the oral closing movements for a "b" sound. Loads were introduced randomly in approximately 15% of the trials to minimize subject anticipation or adaptation. A total of 490 load trials (in five naive subjects) were distributed within a restricted interval (100 ms) centered on the initiation of agonist muscle contraction associated with the lip-closing movements. Kinematic adjustments of the upper and lower lips to these perturbations were examined in detail. In all subjects, load-induced changes in upper and lower lip displacement, movement time, and closing velocity were statistically significant and observed the first time a perturbation was introduced. Load timing variations within the target interval resulted in systematic changes in the site of the compensatory adjustments (upper versus lower lip) and in the magnitude of the kinematic responses. These kinematic changes appeared to reflect the dynamic nature of underlying control processes and clearly contrasted the different response characteristics of autogenic (lower lip) and nonautogenic (upper lip) compensatory actions. Although both upper and lower lip adjustments contributed to perturbation compensations, autogenic responses were found to predominate when loads occurred 20-55 ms before muscle activation. For these early loads, autogenic responses provided approximately 75% of the total compensation. For later loads, when the evolving speech motor action was more time constrained, nonautogenic (open-loop) compensations predominated, providing approximately 65% of the total compensation. The variations in upper and lower lip compensatory response magnitude did not parallel the time course of facial muscle activation. Lower lip kinematic adjustments were reduced 10-15 ms prior to the onset of agonist muscle activation, whereas upper lip adjustments increased in magnitude 10-20 ms after agonist onset. Apparently the dynamic modulation of these responses is controlled independently from facial motoneuron excitation, possibly involving sensorimotor processing via supranuclear centers. Overall the compensatory movement displacements were highly related to the magnitude of the perturbation displacement, especially for loads introduced prior to agonist muscle onset, reflecting a well-calibrated readjustment.(ABSTRACT TRUNCATED AT 400 WORDS)

Dynamic control of the perioral system during speech: kinematic analyses of autogenic and nonautogenic sensorimotor processes.

The present paper provides some hypotheses concerning the role of sensorimotor mechanisms in the coordination and programming of multimovement behaviors. The primary database is from experiments on the control of speech, a motor behavior that inherently requires multimovement coordination. From these data, it appears that coordination may be implemented by calibrated, sensorimotor actions which couple multiple movements for the accomplishment of common functional goals. The data from speech and select observations in other motor systems also reveal that these sensorimotor linkages are task-dependent and may underlie the intermovement motor equivalence that characterizes many natural motor behaviors. In this context, it is hypothesized also that motor learning may involve the calibration of these intermovement sensorimotor actions. These observations in turn provide some alternative perspectives on the concept of a motor program, primarily suggesting that individual movements and muscle contractions are not wholly prespecified, but shaped by sensorimotor adjustments.

Control of multimovement coordination: sensorimotor mechanisms in speech motor programming.

1. Brief increases or decreases in vertical load force were applied to an object held between the thumb and finger. Grip force increases occurred consistently from 60 to 90 ms after onset of the load force increase. These responses did not adapt and were typically from 100 to 200 ms in duration. Reductions in object load force yielded rapid reductions in grip force at latencies comparable to those for load increases. 2. Response magnitude was proportional to the size or velocity of the load force increment, but did not vary with the level of the preexisting grip force. Thus these responses did not maintain the grip force at a specified level above the object's slip point. 3. Grip force responses were abolished or substantially reduced when loads were delivered directly to the hand rather than to the object. In contrast, force responses were not always abolished upon anesthetization of the thumb and finger. These results are discussed in relation to the role of cutaneous mechano-receptors of the digital pulps and proprioceptors of the arm and hand for providing necessary afferent information utilized in load-related grip force modulation. 4. Rapid and automatic grip force adjustments to load force variations may contribute importantly to grasp tasks in which the load forces vary dynamically and without complete predictability, such as in the manipulation of tools or objects that contact the environment.

James H. Abbs

Papers

Finger movement responses of cutaneous mechanoreceptors in the dorsal skin of the human hand

Control of complex motor gestures: orofacial muscle responses to load perturbations of lip during speech.

Dynamic control of the perioral system during speech: kinematic analyses of autogenic and nonautogenic sensorimotor processes.

Control of multimovement coordination: sensorimotor mechanisms in speech motor programming.

Grip force adjustments evoked by load force perturbations of a grasped object.