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Background Adaptation to a constant sensory stimulus involves many sites along the path of sensory volleys towards perception. The evaluation of such phenomenon may be of clinical interest. We studied adaptation to a constant temperature stimulus in healthy subjects to set normative data and in patients with sensory polyneuropathy (SPN), as proof of concept. Methods Twenty-six healthy subjects and 26 patients with SPN in the context of chemotherapy treatment with oxaliplatin for colon cancer were instructed to express through an electronic VAS system (eVAS); the level of sensation felt when a thermode set at either 39º, 41º, 43º, 45º or 47º was applied to their ventral forearm. Results The eVAS recordings showed typically an abrupt onset that slowed to approach maximum sensation and continued with a slow decrease indicating adaptation. The time to respond (TR), the velocity of the initial response (VR), the maximum sensation (MA), the time to reach MA (MAt), the onset of adaptation (AO) and the decrease in the sensation level with respect to MA at 30 s after stimulus application (SL30), were dependent on the temperature level in all subjects. However, patients showed significantly delayed TR, slowed VR, decreased MA, delayed AO and reduced SL30, with respect to healthy subjects. Differences were more pronounced at low-temperature levels, with absent AO in 25 patients versus 2 healthy subjects at temperatures of 39º and 41ºC. Conclusion The study of adaptation to a constant temperature stimulus can furnish valuable data for the assessment of patients with SPN. SIGNIFICANCE: We studied perceptual changes in the intensity of thermoalgesic sensation during 30 s of constant temperature stimulation after an abrupt initial contact in healthy subjects and patients with sensory polyneuropathy. Patients showed delayed time to respond, decreased maximal sensation and reduced adaptation with respect to healthy subjects. Differences were more pronounced at low and intermediate temperatures (39ºC to 43ºC). The method is of easy implementation and shows clinically relevant abnormalities in patients with sensory polyneuropathy.

A startling auditory stimulus (SAS) induces a reflex response involving, among other reactions, a strong contraction of the orbicularis oculi muscle (OOc) and subsequent eye closure. A SAS also induces the StartReact effect, a significant shortening of reaction time in subjects ready for task execution. We examined the obvious conflict appearing when a StartReact paradigm requires participants with eyes closed to open their eyes to look for a visual target. We recorded OOc EMG activity and eyelid movements in healthy volunteers who were instructed to open their eyes at perception of a somatosensory imperative stimulus (IS) and locate the position of a Libet's clock's hand shown on a computer screen at 80 cm distance. In 6 out of 20 trials, we delivered a SAS simultaneously with the IS. The main outcome measures were reaction time at onset of eyelid movement and the time gap (TG) separating subjective assessment of the clock's hand position from real IS issuing. Control experiments included reaction time to eye closing and target location with eyes open to the same IS. Reaction time was significantly faster in SAS than in noSAS trials and slower for eye opening than for eye closing in both conditions. In the eye-opening task, TG was significantly shorter in SAS with respect to noSAS trials, despite the presence of the SAS-related burst in the OOc before EMG cessation. Our results indicate that the StartReact effect speeds up eye opening and location of a target in the visual field despite the startle reaction opposing the task.

There has been much debate concerning whether startling sensory stimuli can activate a fast-neural pathway for movement triggering (StartReact) which is different from that of voluntary movements. Activity in sternocleidomastoid (SCM) electromyogram is suggested to indicate activation of this pathway. We evaluated whether SCM activity can accurately identify trials which may differ in their neurophysiological triggering and assessed the use of cumulative distribution functions (CDFs) of reaction time (RT) data to identify trials with the shortest RTs for analysis. Using recent datasets from the StartReact literature, we examined the relationship between RT and SCM activity. We categorised data into short/longer RT bins using CDFs and used linear mixed effects models to compare potential conclusions that can be drawn when categorising data on the basis of RT versus on the basis of SCM activity. The capacity of SCM to predict RT is task-specific, making it an unreliable indicator of distinct neurophysiological mechanisms. Classification of trials using CDFs is capable of capturing potential task- or muscle-related differences in triggering whilst avoiding the pitfalls of the traditional SCM activity based classification method. We conclude that SCM activity is not always evident on trials that show the early triggering of movements seen in the StartReact phenomenon. We further propose that a more comprehensive analysis of data may be achieved through the inclusion of CDF analyses. These findings have implications for future research investigating movement triggering as well as for potential therapeutic applications of StartReact.

Purpose: The purpose of this report is to describe the Global Spine Care Initiative (GSCI) contributors, disclosures, and methods for reporting transparency on the development of the recommendations. Methods: World Spine Care convened the GSCI to develop an evidence-based, practical, and sustainable healthcare model for spinal care. The initiative aims to improve the management, prevention, and public health for spine-related disorders worldwide; thus, global representation was essential. A series of meetings established the initiative’s mission and goals. Electronic surveys collected contributorship and demographic information, and experiences with spinal conditions to better understand perceptions and potential biases that were contributing to the model of care. Results: Sixty-eight clinicians and scientists participated in the deliberations and are authors of one or more of the GSCI articles. Of these experts, 57 reported providing spine care in 34 countries, (i.e., low-, middle-, and high-income countries, as well as underserved communities in high-income countries.) The majority reported personally experiencing or having a close family member with one or more spinal concerns including: spine-related trauma or injury, spinal problems that required emergency or surgical intervention, spinal pain referred from non-spine sources, spinal deformity, spinal pathology or disease, neurological problems, and/or mild, moderate, or severe back or neck pain. There were no substantial reported conflicts of interest. Conclusion: The GSCI participants have broad professional experience and wide international distribution with no discipline dominating the deliberations. The GSCI believes this set of papers has the potential to inform and improve spine care globally. Graphical abstract: These slides can be retrieved under Electronic Supplementary Material.[Figure not available: see fulltext.]

The purpose of this study was to develop recommendations for prevention interventions for spinal disorders that could be delivered globally, but especially in underserved areas and in low- and middle-income countries. We extracted risk factors, associations, and comorbidities of common spinal disorders (e.g., back and neck pain, spinal trauma, infection, developmental disorders) from a scoping review of meta-analyses and systematic reviews of clinical trials, cohort studies, case control studies, and cross-sectional studies. Categories were informed by the Global Spine Care Initiative (GSCI) classification system using the biopsychosocial model. Risk factors were clustered and mapped visually. Potential prevention interventions for individuals and communities were identified. Forty-one risk factors, 51 associations, and 39 comorbidities were extracted; some were associated with more than one disorder. Interventions were at primary, secondary, tertiary, and quaternary prevention levels. Public health-related actions included screening for osteopenia, avoiding exposure to certain substances associated with spinal disorders, insuring adequate dietary intake for vitamins and minerals, smoking cessation, weight management, injury prevention, adequate physical activity, and avoiding harmful clinical practices (e.g., over-medicalization). Prevention principles and health promotion strategies were identified that were incorporated in the GSCI care pathway. Interventions should encourage healthy behaviors of individuals and promote public health interventions that are most likely to optimize physical and psychosocial health targeting the unique characteristics of each community. Prevention interventions that are implemented in medically underserved areas should be based upon best evidence, resource availability, and selected through group decision-making processes by individuals and the community. These slides can be retrieved under Electronic Supplementary Material.

Passive limb displacement is routinely used to assess muscle tone. If we attempt to quantify muscle stiffness using mechanical devices, it is important to know whether kinematic stimuli are able to trigger startle reactions. Whether kinematic stimuli are able to elicit a startle reflex and to accelerate prepared voluntary movements (StartReact effect) has not been studied extensively to date. Eleven healthy subjects were suspended in an exoskeleton and were exposed to passive left knee flexion (KF) at three intensities, occasionally replaced by fast right KF. Upon perceiving the movement subjects were asked to perform right wrist extension (WE), assessed by extensor carpi radialis (ECR) electromyographic activity. ECR latencies were shortest in fast trials. Startle responses were present in most fast trials, yet being significantly accelerated and larger with right versus left KF, since the former occurred less frequently and thus less expectedly. Startle responses were associated with earlier and larger ECR responses (StartReact effect), with the largest effect again upon right KF. The results provide evidence that kinematic stimuli are able to elicit both startle reflexes and a StartReact effect, which depend on stimulus intensity and anticipation, as well as on the subjects' preparedness to respond. This study was supported by Instituto de Salud Carlos III Grant ESPY 1281-15 and Government of Spain Grant PRX12/00349 to Juan M. Castellote. Sí

A combined assessment tool for the perceptual-motor aspects of pain processing will be valuable to clinicians. Fifteen healthy subjects were exposed to contact-heat stimulation (Pathway, Medoc, Israel) to assess perception through a simple task (motor response or conscious appraisal of the time the stimulus was felt) or with a dual task (both responses). The outcome measure was the temporal relationship between contact heat evoked potentials (CHEPS), reaction time (RT) and conscious awareness (AW). There were different temporal profiles for CHEPs, RT and AW to changes in stimulus intensity, AW being the least affected. Performing the dual task led to a significantly more pronounced effect on RT than on AW, while CHEPS were not influenced by task performance. Our results support the dissociation between physiological, behavioral and cognitive events elicited by nociceptive stimuli. The time of conscious appraisal of stimulus occurrence is a complementary information to other responses such as evoked potentials or behavioral tasks. The combined assessment of physiological and behavioral aspects of pain processing may provide clinicians with information on the different paths followed by nociceptive afferent inputs in the central nervous system. The study was carried out in part thanks to funds from grants: PI1300526 from Fondo de Investigaciones Sanitarias to J. Valls-Sole, ESPY-112/18 from Instituto de Salud Carlos III and Grant PRX12/00349 from Government of Spain to J. M. Castellote. Sí

Purpose: Spinal disorders, including back and neck pain, are major causes of disability, economic hardship, and morbidity, especially in underserved communities and low- and middle-income countries. Currently, there is no model of care to address this issue. This paper provides an overview of the papers from the Global Spine Care Initiative (GSCI), which was convened to develop an evidence-based, practical, and sustainable, spinal healthcare model for communities around the world with various levels of resources. Methods: Leading spine clinicians and scientists around the world were invited to participate. The interprofessional, international team consisted of 68 members from 24 countries, representing most disciplines that study or care for patients with spinal symptoms, including family physicians, spine surgeons, rheumatologists, chiropractors, physical therapists, epidemiologists, research methodologists, and other stakeholders. Results: Literature reviews on the burden of spinal disorders and six categories of evidence-based interventions for spinal disorders (assessment, public health, psychosocial, noninvasive, invasive, and the management of osteoporosis) were completed. In addition, participants developed a stratification system for surgical intervention, a classification system for spinal disorders, an evidence-based care pathway, and lists of resources and recommendations to implement the GSCI model of care. Conclusion: The GSCI proposes an evidence-based model that is consistent with recent calls for action to reduce the global burden of spinal disorders. The model requires testing to determine feasibility. If it proves to be implementable, this model holds great promise to reduce the tremendous global burden of spinal disorders. Graphical abstract: These slides can be retrieved under Electronic Supplementary Material.[Figure not available: see fulltext.].

The purpose of this report is to describe the development of an evidence-based care pathway that can be implemented globally. The Global Spine Care Initiative (GSCI) care pathway development team extracted interventions recommended for the management of spinal disorders from six GSCI articles that synthesized the available evidence from guidelines and relevant literature. Sixty-eight international and interprofessional clinicians and scientists with expertise in spine-related conditions were invited to participate. An iterative consensus process was used. After three rounds of review, 46 experts from 16 countries reached consensus for the care pathway that includes five decision steps: awareness, initial triage, provider assessment, interventions (e.g., non-invasive treatment; invasive treatment; psychological and social intervention; prevention and public health; specialty care and interprofessional management), and outcomes. The care pathway can be used to guide the management of patients with any spine-related concern (e.g., back and neck pain, deformity, spinal injury, neurological conditions, pathology, spinal diseases). The pathway is simple and can be incorporated into educational tools, decision-making trees, and electronic medical records. A care pathway for the management of individuals presenting with spine-related concerns includes evidence-based recommendations to guide health care providers in the management of common spinal disorders. The proposed pathway is person-centered and evidence-based. The acceptability and utility of this care pathway will need to be evaluated in various communities, especially in low- and middle-income countries, with different cultural background and resources. These slides can be retrieved under Electronic Supplementary Material. The Global Spine Care Initiative and this study were funded by grants from the Skoll Foundation and NCMIC Foundation. World Spine Care provided financial management for this project. The funders had no role in study design, analysis, or preparation of this paper. Sí

OBJECTIVE: The purpose of this review was to identify risk factors, prognostic factors, and comorbidities associated with common spinal disorders. METHODS: A scoping review of the literature of common spinal disorders was performed through September 2016. To identify search terms, we developed 3 terminology groups for case definitions: 1) spinal pain of unknown origin, 2) spinal syndromes, and 3) spinal pathology. We used a comprehensive strategy to search PubMed for meta-analyses and systematic reviews of case-control studies, cohort studies, and randomized controlled trials for risk and prognostic factors and cross-sectional studies describing associations and comorbidities. RESULTS: Of 3,453 candidate papers, 145 met study criteria and were included in this review. Risk factors were reported for group 1: non-specific low back pain (smoking, overweight/obesity, negative recovery expectations), non-specific neck pain (high job demands, monotonous work); group 2: degenerative spinal disease (workers' compensation claim, degenerative scoliosis), and group 3: spinal tuberculosis (age, imprisonment, previous history of tuberculosis), spinal cord injury (age, accidental injury), vertebral fracture from osteoporosis (type 1 diabetes, certain medications, smoking), and neural tube defects (folic acid deficit, anti-convulsant medications, chlorine, influenza, maternal obesity). A range of comorbidities was identified for spinal disorders. CONCLUSION: Many associated factors for common spinal disorders identified in this study are modifiable. The most common spinal disorders are co-morbid with general health conditions, but there is a lack of clarity in the literature differentiating which conditions are merely comorbid versus ones that are risk factors. Modifiable risk factors present opportunities for policy, research, and public health prevention efforts on both the individual patient and community levels. Further research into prevention interventions for spinal disorders is needed to address this gap in the literature. The Global Spine Care Initiative (GSCI) was funded by grants from the Skoll Foundation (www.skoll.org) and NCMIC Foundation (www.ncmicfoundation.org) (SH). World Spine Care provided financial management for the GSCI project. The grantors had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Open access funding for this study provided by Brighthall, Inc. BNG and CDJ are officers of Brighthall. Sí

Objective Fast and accurate movements are often performed in response to a sensory signal. In reaction time tasks, execution of open loop movements is speeded up when a startling auditory stimulus (SAS) is applied together with the imperative signal (IS). In this study, we examined the effects of a SAS on the performance of a task that demands accuracy. Methods Nine subjects were asked to move a monitored pen to a target point located in a table at a fixed angular distance of 30 degrees from a start point. The target was a spot of three possible diameters: 5, 10, and 20 mm. Finger force for pen holding, pen tip pressure against the table and kinematic variables of the forearm movement were measured for three conditions: control, SAS delivered at IS (SAS-IS trials) and SAS delivered during movement execution (SAS-MOV trials). Results Two movement phases could be identified in the movement trajectory and force profile. The first phase, ballistic, was significantly shortened in SAS-MOV trials, with earlier and larger peak velocity and peak force with respect to control trials. The second phase, slow approach to target, was longer in SAS-IS trials but not in SAS-MOV trials. Accuracy was maintained throughout all conditions and stimulation modes. Conclusions A SAS speeds up only the first (ballistic) part of the movement in an accuracy task. Slower target approach compensates for the accelerated initial movement. No changes in the last part of the movement are seen when a SAS is delivered after movement onset. Significance The StartReact effect is restricted to the onset of a complex movement, when muscles are activated in a ballistic mode, without feedback.

In certain circumstances, words can be uttered as an involuntary action. We hypothesize that, once pronunciation of a word is fully prepared it can be triggered as a reflex with no need for cortical processing. We used modified protocols of picture naming tasks, with different levels of cognitive demands, to measure reaction time to word pronunciation (RTWP). In test trials, picture presentation was accompanied by a startling auditory stimulus (SAS). When one and the same picture was repeatedly shown, SAS shortened RTWP by about 30% (StartReact effect), which did not occur when random pictures were shown. If subjects were led to learn which picture was to appear after repeated presentation of three pictures in sequence, they exhibited again the StartReact effect. We conclude that word pronunciation may be fully prepared for execution in absence of cognitive demands. However, the StartReact effect is inhibited during cognitive tasks.

PURPOSE: Understanding the presentation of spinal cord injury (SCI) due to tumours considering population distribution and temporal trends is key to managing SCI health services. This study quantified incidence rates, function scores, and trends of SCI due to tumour or metastasis over an 18-year time period in a defined region in Spain. METHODS: A retrospective cohort study included in-and outpatients with nontraumatic SCI due to tumour or metastasis admitted to a metropolitan hospital in Spain between 1991 and 2008. Main outcome measures were crude and age- and sex-adjusted incidence rates, tumour location and type, distribution by spinal level, neurological level of injury, and impairment ASIA scores. RESULTS: Primary tumour or metastasis accounted for 32.5% of nontraumatic SCI with an incidence rate of 4.1 per million population. Increasing rates with age and over time were observed. Major pathology groups were intradural-extramedullary masses from which meningiomas and neurinomas accounted for 40%. Lesions were mostly incomplete with predominant ASIA Grade D. CONCLUSIONS: Increasing incidence rates of tumour-related SCI over time in the middle-aged and the elderly suggest a growing need for neurooncology health resources in the future. This study was supported by the Ministry of Education (Grant SB2009-0175 to Maayken Elizabeth Louise van den Berg) and the Carlos III Institute of Health (Grants TPY 1529/07, TPY 1444/08, and ESPY 1281/15 to Juan M. Castellote). The authors would like to thank the staff of the Servet Hospital and especially the medical staff of the SCI unit at the Rehabilitation Service that facilitated access to information. Sí

European Higher Education Area includes standards for graduate and postgraduate teaching, as well as a psycho-pedagogy framework. Improving learning strategies of students in occupational medicine, from the teachers point of view, deals fundamentally with improving learning environment. The goal of the present study is to assess and profile learning strategies in occupational medicine teaching modules. A sample with 53 undergraduate students who were enrolled in occupational health classes participate in the study. The students filled the Study Process Questionnaire (R-SPQ-2F). Strategies used by students were related with the learning assessment performed at the end of the teaching term. Students expressed a significantly higher use of deep strategies (16±4) than surface strategies (14±2). Regarding performance, there was a direct relationship between deep strategies score and the learning assessment results. The findings support that, in occupational medicine, knowledge of learning strategies profiles will help to improve education. In order to improve teaching standards it is advisable applying assessment systems that allow adapting teaching methods to students’ profiles.

Motor evoked potentials (MEPs) in the right first dorsal interosseous (FDI) muscle elicited by transcranial magnetic stimulation of left motor cortex were assessed in ten healthy subjects during maintenance of a fixed FDI contraction level. Subjects maintained an integrated EMG (IEMG) level with visual feedback and reproduced this level by memory afterwards in the following tasks: stationary FDI muscle contraction at the level of 40 ± 5 % of its maximum voluntary contraction (MVC; 40 % task), at the level of 20 ± 5 % MVC (20 % task), and also when 20 % MVC was preceded by either no contraction (0-20 task), by stronger muscle contraction (40-20 task) or by no contraction with a previous strong contraction (40-0-20 task). The results show that the IEMG level was within the prescribed limits when 20 and 40 % stationary tasks were executed with and without visual feedback. In 0-20, 40-20, and 40-0-20 tasks, 20 % IEMG level was precisely controlled in the presence of visual feedback, but without visual feedback the IEMG and force during 20 % IEMG maintenance were significantly higher in the 40-0-20 task than those in 0-20 and 40-20 tasks. That is, without visual feedback, there were significant variations in muscle activity due to different prehistory of contraction. In stationary tasks, MEP amplitudes in 40 % task were higher than in 20 % task. MEPs did not differ significantly during maintenance of the 20 % level in tasks with different prehistory of muscle contraction with and without visual feedback. Thus, in spite of variations in muscle background activity due to different prehistory of contraction MEPs did not vary significantly. This dissociation suggests that the voluntary maintenance of IEMG level is determined not only by cortical mechanisms, as reflected by corticospinal excitability, but also by lower levels of CNS, where afferent signals and influences from other brain structures and spinal cord are convergent.

The aim of this study is to compare the properties of free-walking at a natural pace between mild Parkinson&rsquo, s disease (PD) patients during the ON-clinical status and two control groups. In-shoe pressure-sensitive insoles were used to quantify the temporal and force characteristics of a 5-min free-walking in 11 PD patients, in 16 young healthy controls, and in 12 age-matched healthy controls. Inferential statistics analyses were performed on the kinematic and kinetic parameters to compare groups&rsquo, performances, whereas feature selection analyses and automatic classification were used to identify the signature of parkinsonian gait and to assess the performance of group classification, respectively. Compared to healthy subjects, the PD patients&rsquo, gait pattern presented significant differences in kinematic parameters associated with bilateral coordination but not in kinetics. Specifically, patients showed an increased variability in double support time, greater gait asymmetry and phase deviation, and also poorer phase coordination. Feature selection analyses based on the ReliefF algorithm on the differential parameters in PD patients revealed an effect of the clinical status, especially true in double support time variability and gait asymmetry. Automatic classification of PD patients, young and senior subjects confirmed that kinematic predictors produced a slightly better classification performance than kinetic predictors. Overall, classification accuracy of groups with a linear discriminant model which included the whole set of features (i.e., demographics and parameters extracted from the sensors) was 64.1%.

Animal-assisted therapy (AAT) may affect health via an increase in perceived social support and social interaction. A meta-analysis was conducted to determine its effects on selected populations with poor social functioning. Studies involving elderly participants and those with depression and schizophrenia were searched in Medline, PsycINFO and Cochrane up to January 2009. Matched or controlled trials incorporating pre- and post-test outcome measures and with at least five participants subjected to a multiple-day AAT intervention were selected (n=21). Participants' characteristics, study design, intervention features, outcome variables, reported effects and study quality were retrieved. Design-specific effect sizes were pooled using random-effects models. Heterogeneity of effects by study characteristics, including target population and intervention features, was explored through meta-regression. Pooled effect sizes were calculated for social functioning, depression, anxiety, behavioural disturba...

Spinal cord injury (SCI) leading to neurological deficits produces long-term effects that persist over a lifetime. Survival analysis of patients with SCI, at individual and population level, is important for public health management and the assessment of treatment achievements. The current study evaluated survival following traumatic and non-traumatic SCI worldwide. A systematic review was conducted, and all included papers were assessed for quality using a purposely designed assessment form. Survival data were presented in Kaplan-Meier curves and compared using the log-rank test. Sixteen studies were included of which 11 concerned traumatic SCI, four non-traumatic SCI, and one both. Crude standard mortality rates (SMRs) revealed that overall mortality in SCI is up to three times higher than in the general population. Survival rates were statistically significantly lower in non-traumatic SCI than in traumatic SCI (log-rank p = 0.000). Age at injury, neurological level, extent of lesion, and year of injury have been described as predictors of survival. Causes of death stem from secondary complications, with failure of the respiratory system being the leading cause. This is the first systematic literature review on survival analysis following SCI worldwide. An increase in survival over time was found. However, the SMRs of individuals with SCI still exceed those of an age-matched non-disabled population, mainly due to secondary complications. Lower survival rates were observed in non-traumatic SCI compared with traumatic SCI.

Introduction Utterance of a word may be an involuntary action. We hypothesize that, once pronunciation of a word is fully prepared it can be triggered as a reflex with no need for cortical processing. Methods We used modified protocols of picture naming tasks, with different levels of cognitive demands, to measure the reaction time of word pronunciation (RTWP). In test trials, picture presentation was accompanied by a startling auditory stimulus (SAS). Results When one and the same picture was repeatedly shown, SAS shortened RTWP by about 30% (StartReact effect), which did not occur when random pictures were shown. If subjects were led to learn which picture was to appear after repeated presentation of three pictures in sequence, they exhibited again the StartReact effect. Conclusion We conclude that, when fully prepared, pronunciation of words can be triggered as a SAS-induced subcortical motor reflex. However, the StartReact effect is inhibited during cognitive tasks.

Background: Incidence studies of spinal cord injury (SCI) are important for health-care planning and epidemiological research. This review gives a quantitative update on SCI epidemiology worldwide through a statistical evaluation of incidence rates. Methods: A systematic review was conducted. For each study, the crude rate ratio was calculated and, when possible, age- and gender-adjusted incidence rate ratios with 95% CI were determined by direct adjustment or using Poisson regression. Results: Thirteen studies were included. Annual crude incidence rates in traumatic SCI varied from 12.1 per million in The Netherlands to 57.8 per million in Portugal. Compared to the Portuguese reference study, incidence rates showed a 3-fold variation, with the highest rates in Canada and Portugal. Most traumatic SCI studies showed a bimodal age distribution. The first peak was found in young adults between 15 and 29 years and a second peak in older adults (mostly ≧65 years). Motor vehicle accidents and falls were the most prevalent causes of injury accounting for nearly equal percentages. In contrast, another age pattern in non-traumatic SCI reflected steadily increasing incidence with advancing age. Conclusions: The results show significant variation in SCI incidence with changing epidemiological patterns. A trend towards increased incidence in the elderly was observed, likely due to falls and non-traumatic injury.

Movement execution is speeded up when a startle auditory stimulus is applied with an imperative signal in a simple reaction time task experiment, a phenomenon described as StartReact. The effect has been recently observed in a step adjustment task requiring fast selection of specific movements in a choice reaction time task. Therefore, we hypothesized that inducing a StartReact effect may be beneficial in obstacle avoidance under time pressure, when subjects have to perform fast gait adjustments. Twelve healthy young adults walked on a treadmill and obstacles were released in specific moments of the step cycle. On average the EMG onset latency in the biceps femoris shortened by 20% while amplitude increased by 50%, in trials in which an auditory startle accompanied obstacle avoidance. The presentation of a startle increased the probability of using a long step strategy, enlarged stride length modifications and resulted in higher success rates, to avoid the obstacle. We also examined the effects of the startle in a condition in which the obstacle was not present in comparison to a condition in which the obstacle was visibly present but it did not fall. In the latter condition, the obstacle avoidance reaction occurred with a similar latency but smaller amplitude as in trials in which the obstacle was actually released. Our results suggest that the motor programmes used for obstacle avoidance are probably stored at subcortical structures. The release of these motor programmes by a startling auditory stimulus may combine intersensory facilitation and the StartReact effect.

Simple ballistic movements are executed faster in reaction time task paradigms when the imperative signal (IS) is accompanied by a startling auditory stimulus (SAS). We examined whether this effect also occurs in complex movements such as the sit-to-stand manoeuvre (STS). Nine healthy volunteers performed STS to visual IS, either presented alone (control trials) or together with SAS (test trials). Reaction time, measured as the time between IS and take-off (TO), was significantly shortened in test trials when SAS was applied at an interval of 0 ms with respect to IS. The onset latency of EMG bursts recorded from tibialis anterior, lumbar paraspinal, quadriceps and biceps femoris muscles reduced proportionally to the shortening of TO. However, these effects were not observed if SAS was delivered 150 ms after IS, when the manoeuvre had already started. Our results suggest that stimuli acting on subcortical motor structures speed-up but do not otherwise interfere with the execution of the motor programs underlying the STS manoeuvre.

Background and Aims Few large studies have examined the relationship between spinal cord injury (SCI) and lipid profile. We studied serum lipid concentrations in subjects with traumatic SCI in relation to the degree of neurological involvement and time since injury, and compared them with values from a reference sample for the Spanish population (DRECE study). Materials and Methods A retrospective cohort was built from 177 consecutive cases with traumatic SCI admitted to the SCI unit of the Miguel Servet Hospital in Aragon (Spain). Outcome measures (cholesterol, triglycerides, HDL-c and LDL-c levels) were analyzed according to the ASIA Impairment Scale (AIS), neurological level of injury (involvement of all limbs vs. only lower limbs), and time since injury. All analyses were adjusted for age and sex. Results Cases without preserved motor function (AIS A or B) had lower total and HDL cholesterol than the others (-11.4 [-21.5, -1.4] mg/dL total cholesterol and -5.1 [-8.8, -1.4] mg/dL HDL-c), and cases with all-limb involvement had lower total, HDL, and LDL cholesterol than those with only lower-limb involvement (-14.0 [-24.6, -3.4]mg/dL total cholesterol, -4.1 [-8.0, -0.2] mg/dL HDL-c, and -10.0 [-19.7, -0.3]mg/dL LDL-c) (all p, Dr. Laclaustra was supported in part by grants FIS CP08/00112 and PI10/00021 from the Spanish Instituto de Salud Carlos III. Dr. Castellote was supported in part by grants TPY 1115/07, PI13/ 00526, TPY 1444/08 and ESVI 1338/12-1 from the Instituto de Salud Carlos III. Dr. Hurtado was supported by Fellowship N°088-FINCyT-BDE-2014 from the Peruvian government

The size of the response to a startling auditory stimulus (SAS) may reflect the excitability of the reticulospinal tract. In this study, we examined whether there was any excitability change in the reticulospinal tract during preparation for execution of two types of choice reaction time task: a forced choice reaction time task (fCRT) and a Go/no-Go task (GnG). In 13 healthy volunteers we used three types of trials: control trials in which subjects were requested to perform ballistic wrist movements during fCRT or GnG tasks; test trials in which a SAS was presented with the visual cue, and baseline trials in which SAS was presented alone. Latency and area of the responses to SAS were measured in the orbicularis oculi and in the sternocleidomastoid (SCM) muscles. The results obtained in baseline trials were used to calculate the mean resting baseline excitability level of the reticulospinal tract for each individual, and the values obtained in test trials were expressed as percentages of mean baseline for normalization of data from all individuals. The area of the responses to SAS in SCM was significantly larger in fCRT than in GnG (p=0.002). There was a significant shortening of reaction time in test trials that was inversely correlated with area of SCM (p

The control of eye movements depends in part on subcortical motor centres. Gaze is often directed towards salient visual stimuli of our environment with no conscious voluntary commands. To further understand to what extent preprogrammed eye movements can be triggered subcortically, we carried out a study in normal volunteers to examine the effects of a startling auditory stimulus (SAS) on externally guided saccades. A peripheral visual cue was presented in the horizontal plane at a site distant 15 degrees from the fixation point, and subjects were instructed to make a saccade to it. SAS was presented together with the peripheral visual cue in 20% of trials. To force rapid visual fixation at the end of the saccade, targets were loaded with a second cue, a small arrow pointing towards the right or the left (or a neutral sign), not distinguishable with peripheral vision. Subjects were requested to perform a flexion/extension wrist movement, according to the direction of the arrow (or not to move if the second cue was the neutral sign). SAS presented together with the visual target caused a significant shortening of the latency of saccadic movements. The wrist movements performed as a response to the second cue had similar reaction times regardless of whether the trial contained a SAS or not. Our results show that voluntary saccades to peripheral targets are speeded up by activation of the startle circuit, and that this effect does not cause a significant disturbance in the execution of simple in-target cues. These results suggest that subcortical structures play a main role in preparation of externally guided saccades.

The execution of a ballistic movement within a reaction time task paradigm is significantly speeded up when an unexpected startling auditory stimulus (SAS) is delivered together with the imperative signal. Using Libet's clock, we investigated whether acceleration involves also the subjective appraisal of the time of task execution. In trials containing the SAS, reaction time shortened to 68.7% of control values. However, subjective judgment of task execution remained a similar time with respect to the imperative signal as in control trials. The dissociation between task execution and its subjective perception indicates the existence of separate circuits for action execution and action awareness.

Background Kinematic stimuli are used for both assessment and treatment in neurorehabilitation. A patient’s voluntary or reflex response may be affected by a startle reaction. We therefore explored whether certain kinematic stimuli are able to elicit a startle reaction. Methods Eleven healthy subjects were suspended in a Lokomat system and were exposed to unexpected passive left knee flexion at 3 velocities (6, 60, 240°/s). Subjects were asked to perform a right wrist extension as soon as they felt their leg move (conditions: 6-React, 60-React, 240-React, respectively). In some 240°/s trials movement onset was preceded by a low-intensity electrical pre-pulse to the left index finger (240-Prep-React). We recorded EMG activity from right orbicularis oculi and sternocleidomastoid muscles to assess startle responses, from left quadriceps muscle to obtain stretch reflexes, and from right wrist extensors to assess reaction time. Results Startle responses were present in most 240-Reacttrials, as evidenced by (1) EMG activity in orbicularis oculi and/or sternocleidomastoid, (2) significant reaction time shortening in wrist extensors, and (3) stretch reflex latency shortening in quadriceps, as compared to responses without startle reaction. Only few trials at lower angular velocities resulted in startle responses. In 240-Prep-React trials no startle responses occurred. Conclusions Kinematic stimuli of high angular velocity, used to assess muscle stiffness, may elicit a generalized startle reaction, which in turn may modulate stretch reflex latencies of the muscle tested in a passive movement paradigm.

Galvanic vestibular stimulation (GVS) evokes responses in muscles of both legs when bilateral stimuli are applied during normal stance. We have used this technique to assess whether asymmetrical standing alters the distribution of responses in the two legs. Subjects stood either asymmetrically with 75% of their body weight on one leg or symmetrically with each leg taking 50% of their body weight. The net response in each leg was taken from changes in ground reaction force measured from separate force plates under each foot. The net force profile consisted of a small initial force change that peaked at approximately 200 ms followed by an oppositely directed larger component that peaked at approximately 450 ms. We analysed the second force component since it was responsible for the kinematic response of lateral body sway and tilt towards the anode. In the horizontal plane, both legs produced lateral force responses that were in the same direction but larger in the leg ipsilateral to the cathodal ear. There were also vertical force responses that were of equal size in both legs but acted in opposite directions. When subjects stood asymmetrically the directions of the force responses remained the same but their magnitudes changed. The lateral force response became 2-3 times larger for the more loaded leg and the vertical forces increased 1.5 times on average for both legs. Control experiments showed that these changes could not be explained by either the consistent (5 deg) head tilt towards the side of the loaded leg or the changes in background muscle activity associated with the asymmetrical posture. We conclude that the redistribution of force responses in the two legs arises from a load-sensing mechanism. We suggest there is a central interaction between load-related afferent input from the periphery and descending motor signals from balance centres.

Corticosteroids are probably an effective treatment for some types of neuropathic pain and complex regional pain syndromes. This study examined the effects of systemic methylprednisolone (MP) on acute nociception and on pain behavior and hyperalgesia in normal and neuropathic rats. There was no dose-response to intraperitoneal MP (up to 12 mg/kg) for nociceptive thresholds to heat (Peltier) or mechanical (analgesy-meter and von Frey fibers) stimuli in normal rats. Chronic high dose MP (3 mg/kg per day for 21 days) also had no effect on acute nociceptive thresholds in normal rats. After sciatic nerve section in rats a saphenous nerve mediated hyperalgesia to heat and mechanical stimuli gradually developed over 21 days. High dose MP (3 mg/kg per day for 21 days) had no effect on this adjacent neuropathic hyperalgesia. When systemic MP was started immediately after bilateral sciatic and saphenous nerve transection there was a dose-dependent reduction in autotomy behavior. Substance P has been proposed as a mediator of neuropathic pain and edema. Single dose MP (12 mg/kg) slightly reduced the substance P mediated extravasation induced with electrical stimulation of the saphenous nerve. Chronic MP (3.4 mg/kg per day for 28 days) severely reduced the neurogenic extravasation induced with saphenous nerve stimulation. Sciatic sectioned rats developed hindpaw edema between 7 and 14 days after surgery, and this neuropathic edema did not develop in rats chronically treated with MP (3.4 mg/kg per day). These results demonstrate that corticosteroids did not affect nociceptive thresholds in normal or neuropathic hyperalgesic rats. Chronic steroid treatment did prevent the development of autotomy and neuropathic edema, and completely blocked neurogenic extravasation, findings consistent with the hypothesis that primary afferent substance P release mediates autotomy pain behavior and neuropathic edema. This may be a relevant model for examining the effects of corticosteroids on neuropathic pain and complex regional pain syndromes.

Preparation of the motor system for movement execution involves an increase in excitability of motor pathways. In a reaction time task paradigm, a startling auditory stimulus (SAS) delivered together with the imperative signal (IS) shortens reaction time significantly. In self-generated tasks we considered that an appropriately timed SAS would have similar effects. Eight subjects performed a ballistic wrist extension in two blocks: reaction, in which they responded to a visual IS, and action, in which they moved when they wished within a predetermined time window. In 20–25% of the trials, a SAS was applied. We recorded electromyographic activity of wrist extension and wrist movement kinematic variables. No effects of SAS were observed in action trials when movement was performed before or long after SAS application. However, a cluster of action trials was observed within 200 ms after SAS. These trials showed larger EMG bursts, shorter movement time, shorter time to peak velocity, and higher peak velocity than other action trials ( for all), with no difference from Reaction trials containing SAS. The results show that SAS influences the execution of self-generated human actions as it does with preprogrammed reaction time tasks during the assumed building up of preparatory activity before execution of the willed motor action.

OBJECTIVES: To analyse the relationships between chronic conditions, body functions, activity limitations and participation restrictions in the International Classification of Functioning, Disability and Health (ICF) framework. DESIGN: A cross-sectional study. SETTING: 2 geographical areas in the Autonomous Region of Aragon, Spain, namely, a rural area, Cinco Villas, and an urban area in the city of Zaragoza. PARTICIPANTS: 864 individuals selected by simple random sampling from the register of Social Security card holders, aged 50 years and over, positive to disability screening. MAIN OUTCOME MEASURES: ICF Checklist-body function domains, WHO Disability Assessment Schedule 2.0 (WHODAS 2.0, 36-item (WHODAS-36)) global scores and medical diagnoses (chronic conditions) from primary care records. RESULTS: Mild disability (WHODAS-36 level 5-24%) was present in 51.5% of the sample. In the adjusted ordinal regression model with WHODAS-36 as the dependent variable, disability was substantially associated with moderate-to-complete impairment in the following functions: mental, OR 212.8 (95% CI 72 to 628.9); neuromusculoskeletal, OR 44.8 (24.2 to 82.8); and sensory and pain, OR 6.3 (3.5 to 11.2). In the relationship between health conditions and body function impairments, the strongest links were seen for: dementia with mental functions, OR 50.6 (25.1 to 102.1); cerebrovascular disease with neuromusculoskeletal function, OR 5.8 (3.5 to 9.7); and chronic renal failure with sensory function and pain, OR 3.0 (1.49 to 6.4). Dementia, OR 8.1 (4.4 to 14.7) and cerebrovascular disease, OR 4.1 (2.7 to 6.4) were associated with WHODAS-36 scores. CONCLUSIONS: Body functions are heterogeneously linked to limitations in activities and restrictions on participation, with the highest impact being due to mental and musculoskeletal functions. This may be relevant for disability assessment and intervention design, particularly if defined on a body function basis. Control of specific health conditions, such as dementia and cerebrovascular disease, appears to be paramount in reducing disability among persons aged 50 years and over. This study was funded by the Carlos III Institute of Health (EPI projects 1637/06 and 1530/07; Health Research Fund grants PI06/1098 and PI07/90206), Convenio Marco IMSERSO-ISCIII reference number STVI 1282/ 15, Consortium for Biomedical Research in Neurodegenerative Diseases (Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas, CIBERNED), Zaragoza Regional Authority and Farasdués Foundation. Sí

Objective Afferent inputs in humans lead to a trace of excitability in the corresponding sensory channel, perception, cognition and prepared motor responses. We investigated how the events related to each of these aspects of sensory processing are affected by stimulus intensity. Methods Nine healthy subjects performed a wrist extension reaction time (RT) task experiment in front of the Libet’s clock in order to assess the time at which they perceived the contact heat stimulus used as imperative signal (awareness = AW). We recorded also the thermoalgesic evoked potentials (N2/P2). Stimuli were either strong (52 °C) or mild (42 °C). We monitored RT, N2 latency, amplitude of N2–P2, and the time of AW for each stimulation condition. Results Usual order of responses was RT, AW, N2. N2–P2 amplitude had a negative correlation with AW ( p Conclusions Reaction time is executed as soon as the imperative signal is processed, while a late cognitive response does not depend on stimulus intensity. Key message The test used allows for separation of perceptual levels in humans.

Background Some skilfulfast activities require control of trajectory and force to fulfill the task. It is known that voluntary reactions can be speeded up by a startling auditory stimulus (SAS) delivered at the same time as the imperative signal (IS), a phenomenon termed Start-React (Valls-Sole et al., 1999). The aim of the present study was to examine how the performance of a task that demands accuracy, mainly in terms of velocity during the trajectory or force control when holding an object, is changed by a SAS timed to occur either at the time of IS or at a pre-determined time interval when movement has already begun and motor control of accurate reaching is expected. Methods Nine subjects performed an accurate elbow extension between two spots placed at an angular distance of 30° when holding with their right hand a pen that monitored, through two strain gauge systems, the force of the subject’s fingers during the hold, and the force at which pen-tip was exposed with table contact. According to block of trials, this end spot had three possible diameters: 5, 10, and 20 mm. Kinematic and force parameters were measured for three conditions, control, with SAS at IS or SAS delivered when movement has already started. Results In SAS trials, there were no evident differences with respect to control trials in the general outline but there were differences in the timing of the events. In SAS-IS trials time to peak velocity was 166 ms (SD = 41 ms), time to peak force was 95 ms (SD = 43 ms) both shorter than in control or SAS delivered when movement began. Peak velocity (315 ± 56 o/s) and peak force (8 ± 2 arbitr. units) were larger for SAS-IS trials than for control or SAS delivered when movement started. Conclusions Startle can advance a task that requires accuracy with velocity and force modulations, but when task onset is already launched there are not evident changes in velocity or force parameters, that seem already prepared.

A startling auditory stimulus (SAS) causes a faster execution of voluntary actions when applied together with the imperative signal in reaction time tasks (the StartReact effect). However, speeding up reaction time may not be the best strategy in all tasks. After a self-initiated fall, the program for landing has to be time-locked to foot contact to avoid damage, and therefore advanced execution of the program would not be convenient. We examined the effects of SAS on the landing motor program in 8 healthy subjects that were requested to let themselves fall from platforms either 50 or 80 cm high at the perception of a visual imperative signal and land on specific targets. In trials at random, SAS was applied either together with the imperative signal (SASIS) or at an appropriate prelanding time (SASPL). As expected, the latency of takeoff was significantly shortened in SASIS trials. On the contrary, the timing of foot contact was not significantly different for SASPL compared with control trials. No changes were observed in the size of the electromyograph bursts in the two experimental conditions with respect to the control condition. Our results indicate that the landing program after a self-initiated fall may in part be organized at the time of takeoff and involve precise information on timing of muscle activation. Once launched, the program is protected against interferences by external inputs.

van den Berg MEL, Castellote JM, Mahillo-Fernandez I, Pedro-Cuesta J. Incidence of nontraumatic spinal cord injury: a Spanish cohort study (1972–2008). Objectives To assess the incidence of nontraumatic spinal cord injury (SCI) in a determined catchment area in Spain, and to evaluate clinical presentations and trends over time. Design Retrospective cohort study between January 1972 and December 2008. Setting A hospital with a specialized SCI unit in a delimited health area in Spain. Participants Hospital inpatients and outpatients with nontraumatic SCI. Interventions Not applicable. Main Outcome Measures Age- and sex-specific incidence rates. Results An adjusted incidence rate of 11.4 per million population was found for this region (12.3 for males, 10.4 for females). A total of 541 cases (53% male) were reported over the 37-year study period. Incidence rates increased with age, with a peak in the 60- to 69-year age group. Tumors were the major cause of SCI. Most of the lesions were at the thoracic level, and C and D were the most frequently observed American Spinal Injury Association grades. Conclusions Nontraumatic SCI shows a relatively even sex distribution and tends to affect older adults. Injuries are mainly attributable to age-related conditions and result mostly in incomplete lesions, which present with paraplegia. This study revealed that although incidence rates for nontraumatic SCI are similar to those previously reported for traumatic SCI in the same area and during the same period, demographic and clinical characteristics are different. These findings have important implications regarding the delivery of rehabilitation and support services to this group of patients, and suggest the need for health policies that involve improved care and prevention resources.

Evoked potentials (EPs) to radiant or contact heat pain stimuli reflect the synchronization of brain activity to noxious inputs. However, we do not know how they relate to conscious aware- ness (AW) of a sensation. In healthy volunteers, we determined the time of AW for thermal noxious and non-noxious sensory inputs and examined its correlation to parametric measures of vertex EPs. Subjects had to report the position of the hand of a Libet's clock at the moment they perceived either a laser or a thermode stimulus. AW was determined after subtracting the position of the clock hand at the moment of stimulus delivery from the one reported by the subject, in ms. Subjects estimated AW in all single trials, including those in which no EPs could be identified. Mean AW was estimated earlier than the corresponding EP latency for both types and intensities of stimuli. There was a weak but significant negative correlation of AW to EPs amplitude, which was higher than the correlation of AW to EPs latency. Our results indicate that the timing of AW is influenced by the subjective relevance of sensory inputs. This feature could be used for the analysis of cognitive aspects of pain processing. Perspective: This article presents a way to measure the subjective awareness of the sensation in- duced by a noxious heat stimulus, either radiant or contact, in healthy human subjects. This method could be used for the analysis of cognitive aspects of pain processing.

An experimental mononeuropathy was produced in rats by unilateral loose ligation of the sciatic nerve, with a contralateral sham surgery. Repeated bilateral sensory testing was performed over time to investigate any threshold differences between the loose ligature side and the contralateral control side. A prolonged reduction in the mean withdrawal threshold to heat was observed on the loose ligature side over the medial dorsum of the hindpaw (MDH), and over the plantar surface of the hindpaw (PSH). Following loose ligature there was also a significant reduction in the von Frey fiber withdrawal thresholds over the lateral dorsum of the hindpaw (LDH) and the medial dorsum of the hindpaw (MDH). In a second experiment the saphenous nerves were transected bilaterally in rats who had an earlier unilateral loose sciatic ligation. The heat hyperalgesia that had been previously observed over the MDH was abolished, and no withdrawal response could be elicited with the largest von Frey fiber over the MDH, indicating that the MDH hyperalgesia induced by sciatic loose ligature was mediated by the saphenous nerve. This adjacent neuropathic hyperalgesia (ANH) resembles the saphenous mediated ANH observed over the MDH following sciatic transection, follows the same temporal course of onset, and may share a similar pathogenesis. The heat threshold over the PSH and the pressure threshold over the LDH were unaffected by the bilateral saphenous transection, demonstrating that following loose sciatic ligation both of these thresholds are mediated by the sciatic nerve.

Long-term incidence studies are required to identify high-risk groups, establish trends, and forecast needs, and thus contribute to health care planning in spinal cord injury (SCI). This study aimed to determine the incidence of traumatic SCI over a 36-year period in Aragón, Spain, and compare rates with other published European estimates. Hospital records from the Servet Hospital, the only specialized SCI unit in the region, of a retrospective cohort with traumatic SCI between January 1972 and December 2008 were reviewed. Specification of SCI patient demographics, injury causes, and related factors was achieved by utilizing medical records available for inpatients, hospital archives, and central databases. A total of 540 cases were reported over the 36-year study period (79% were male). The age- and sex-adjusted incidence rate was 15.5 per million population (18.8 for males and 4.9 for females). Two incidence peaks were suggested, in the 20- to 29-year and 60- to 69-year age groups. Traffic accidents and falls were the main causes of injury. The highest peak occurs in young adults, mainly caused by traffic accidents. The majority of the lesions were at cervical or thoracic level, and ASIA grade A was most frequently observed. The proportion of SCI cases in persons older than 60 years, mostly due to falls, is increasing. The age-adjusted incidence rates found for the region of Aragón in Spain fall within the range of other published European estimates. Comparative epidemiological features for 2001-2008 suggest that there is room for prevention.

Introduction: Voluntary muscle contraction is accompanied by an increase in sympathetic nerve activity. The sympathetic skin response (SSR) is a simple and non-invasive method of autonomic assessment that reflects a synchronized activity of the sweat glands. The aim of our study was to examine the possible relationship between isometric muscle contraction (IC) and changes in the SSR. Methods: In 11 healthy right-handed volunteers, we recorded the SSR from the palm of the hand induced by contralateral triceps IC (mSSR) of variable intensities and durations. We measured the latency, duration, amplitude, waveform and habituation index (HI) of the mSSR, in comparison to the SSR induced by supramaximal electrical stimulation (eSSR) of the brachial plexus at the axillae. Results: A single mSSR was always present at a mean latency of 1.34 ± 0.5 s after the onset of IC. Response amplitude, but not latency or duration, correlated positively with the intensity of IC (r = 0.67; p < 0.001). The latency was shorter, the duration was longer and the HI was reduced in the mSSR in comparison to the eSSRs (ANOVA; p < 0.05 for all comparisons). Conclusions: The mSSR is likely generated endogenously together with the motor commands since inputs from muscle afferents cannot account for response onset. This, together with its low level of habituation, underscores the possibilities of physiological and clinical studies using the mSSR, especially in the assessment of autonomic function in patients with nerve afferent problems. © 2009 Elsevier Ireland Ltd. All rights reserved.

Human gait involves a repetitive leg motor pattern that emerges after gait initiation. While the automatic maintenance of the gait-pattern may be under the control of subcortical motor centres, gait initiation requires the voluntary launching of a different motor program. In this study, we sought to examine how the two motor programmes respond to an experimental manipulation of the timing of gait initiation. Subjects were instructed to start walking as soon as possible at the perception of an imperative signal (IS) that, in some interspersed trials was accompanied by a startling auditory stimulus (SAS). This method is known to shorten the latency for execution of the motor task under preparation. We reasoned that, if the two motor programmes were launched together, the gait-pattern sequence would respond to SAS in the same way as gait initiation. We recorded the gait phases and the electromyographic (EMG) activity of four muscles from the leg that initiates gait. In trials with SAS, latency of all gait initiation-related events showed a significant shortening and the bursts of EMG activity had higher amplitude and shorter duration than in trials without SAS. The events related to gait-pattern were also advanced but otherwise unchanged. The fact that all the effects of SAS were limited to gait initiation suggests that startle selectively can affect the neural structures involved in gait initiation. Additionally, the proportional advancement of the gait-pattern sequence to the end of gait initiation supports the view that gait initiation may actually trigger the inputs necessary for generating the gait-pattern sequence.

Publisher Summary This chapter presents a study to investigate whether the inhibitory effects of the prepulse are different in the condition of motor preparation with respect to that of unexpectancy and whether the inhibition of the startle reaction by a prepulse is associated with the inhibition of the StartReact phenomenon. The chapter demonstrates that the procedure could help in ascertaining whether reflex and volitional components are actually combined in the StartReact phenomenon. Eight healthy volunteers, six men and two women, aged between 25 and 52 years were investigated and the startle reaction was recorded with surface electrodes over the right orbicularis oculi muscle and, in two of the subjects, also over the sternocleidomastoid muscle. The electromyographical (EMG) activity related to the voluntary action was recorded from the wrist extensor muscles. The most important finding of this study is that although a prepulse stimulus had an inhibitory effect on the startle reaction even during preparation for a motor task, the effect was limited to the startle reaction itself and did not influence the startle-induced reaction time acceleration or StartReact phenomenon. This is consistent with the idea that the startle reaction and the StartReact phenomenon are two different effects of a startling auditory stimulus (SAS), with probably different physiological mechanisms.

A startling auditory stimulus delivered during preparation for execution of a ballistic movement in a simple reaction time task experiment induces two effects: a startle response and a reaction time shortening (the StartReact effect). We investigated whether prepulse inhibition of the startle response is effective in suppressing either one of these effects during motor preparation. Twelve healthy volunteers were presented with seven different experimental conditions in random order: while at rest, subjects received a low intensity electrical shock on the middle finger of the left hand (Prep), a loud auditory stimulus (Start), or a combination of these two (PrepStart). While engaged in preparation for a visual simple reaction time task, they were presented with the imperative signal for execution of the reaction (React), or with any of the combinations PrepReact, StartReact, or PrepStartReact. We recorded the EMG activity from the orbicularis oculi and the sternocleidomastoid muscles to assess the startle response, and from the wrist extensor muscles to assess reaction time. The startle response was markedly reduced when Prep was presented 100 ms before Start regardless of whether the subjects were at rest or preparing for the reaction. Reaction time shortened significantly in StartReact trials with respect to React trials, and the percentage shortening was not different in trials in which Prep preceded StartReact and inhibited the startle response. The fact that prepulse inhibition of the startle response is not accompanied by modification of the StartReact effect indicates that there are separate physiological mechanisms for the two effects, an observation that has implications for further understanding of the processes underlying motor preparation for a ballistic reaction.

In preparation for performing task specific ballistic movements, subjects may choose among different possibilities for setting up their motor apparatus, ranging from quiet resting to different types of muscle activation. In the study presented here, we investigated whether differences in the motor set modify either the reaction time or the kinematic characteristics of the movement. Subjects wearing surface EMG recording electrodes in the wrist extensor (WE) and wrist flexor (WF) muscles were requested to react to the presentation of a visual stimulus by performing a ballistic wrist extension movement of an amplitude of about 50 degrees in the following experimental conditions: resting quietly, which was considered as the control condition (CC); isometric contraction (IC), in which subjects were required to activate WE and WF muscles isometrically; rapid oscillations (RO), in which subjects were requested to make a fast oscillatory wrist movement; and slow oscillations (SO), in which subjects were maintaining a slow oscillatory motion of the wrist. To constrain the movement to the wrist joint and limit the action of postural muscles, the subject's forearm and hand were attached to joined non-resistive metallic platforms, allowing for free non-frictional displacement. In the EMG recordings, we measured the size of the EMG bursts in agonist and antagonist muscles, and the inter-burst intervals. In movement recordings, we measured movement onset latency and the velocity profile. Movement onset was delayed in SO with respect to all other conditions. Conversely, peak velocity was larger in all test conditions in comparison to CC. There were no differences in the size of the first EMG burst of the agonist muscle, but significant changes occurred in the subsequent bursts recorded in the agonist and antagonist muscles. Our study indicates that the motor program used to execute a ballistic voluntary movement is influenced by the conditions of the motor system. The configuration of the motor set should be specifically considered in the search for improving the speed of the reaction and the kinematics of ballistic movements.

International audience; A multiple case study was conducted in order to assess three leading theories of developmental dyslexia: (i) the phonological theory, (ii) the magnocellular (auditory and visual) theory and (iii) the cerebellar theory. Sixteen dyslexic and 16 control university students were administered a full battery of psychometric, phonological, auditory, visual and cerebellar tests. Individual data reveal that all 16 dyslexics suffer from a phonological deficit, 10 from an auditory deficit, four from a motor deficit and two from a visual magnocellular deficit. Results suggest that a phonological deficit can appear in the absence of any other sensory or motor disorder, and is sufficient to cause a literacy impairment, as demonstrated by five of the dyslexics. Auditory disorders, when present, aggravate the phonological deficit, hence the literacy impairment. However, auditory deficits cannot be characterized simply as rapid auditory processing problems, as would be predicted by the magnocellular theory. Nor are they restricted to speech. Contrary to the cerebellar theory, we find little support for the notion that motor impairments, when found, have a cerebellar origin or reflect an automaticity deficit. Overall, the present data support the phonological theory of dyslexia, while acknowledging the presence of additional sensory and motor disorders in certain individuals.