A comparison of reward processing during Becker-DeGroot-Marschak and Vickrey auctions: An ERP study.

Vickrey auctions (VA) and Becker-DeGroot-Marschak auctions (BDM) are strategically equivalent demand-revealing mechanisms, differentiated only by a human opponent in the VA, and a random-number-generator opponent in the BDM. Game parameters are such that players are incentivized to reveal their private subjective values (SV) and behavior should be identical in both tasks. However, this has been repeatedly shown not to be the case. In this study, the neural correlates of outcome feedback processing during VA and BDM were directly compared using electroencephalography. Twenty-eight healthy participants bid for household products which were then divided into high- and low-SV categories. The VA included a human opponent deception to induce a social environment, while in reality a random-number-generator was used in both tasks. A P3 component peaking at 336 ms over midline parietal sites showed more positive amplitudes for high bid values, and for win outcomes in the VA but not the BDM. Both auctions also elicited a Reward Positivity potential, maximal at 275 ms along the central midline electrodes, that was not modulated by auction task or SV. Further, an exploratory N170 potential in the right occipitotemporal electrodes and a vertex positive potential component were stronger in the VA relative to the BDM. Results point to an enhanced cortical response to bid outcomes during VA task in a potential component associated with emotional control, and to the occurrence of face-sensitive potentials in VA but not in BDM auction. These findings suggest modulation of bid outcome processing by the social-competitive aspect of auction tasks. Directly comparing two prominent auction paradigms affords the opportunity to isolate the impact of social environment on competitive, risky decision-making. Findings suggest that feedback processing as early as 176 ms is facilitated by the presence of a human competitor, and later processing is modulated by social context and subjective value.

[Revision ACL Reconstruction in Our Study Population]. / Reoperace plastik LCA v nasem souboru.

INTRODUCTION The authors present the long-term clinical outcomes of revision anterior cruciate ligament (ACL) reconstruction. The aim was to compare the surgical technique with respect to the clinical outcomes within 3 years postoperatively. MATERIAL AND METHODS The clinical evaluation of revision anterior cruciate ligament reconstructions performed at our department in 2002-2017 was carried out. A total of 82 patients were included in the study, male as well as female patients. Apart from the clinical outcomes, the associated procedures performed as a consequence of other injuries or damage to other intraarticular structures, the surgical technique as such, potential complications of revision reconstruction and causes of failure were studied. The same criteria were followed up in all the patients - clinical range of motion (ROM) of the operated knee, knee stability - pivot shift test, instrumental Lachman test using Rolimeter, IKDC subjective form, Tegner and Lysholm scores. RESULTS In the group of patients, the surgical technique involved the use of a harmstring tendon autograft as a new graft for revision in 43 patients, a BTB autograft in 25 patients, and a BTB cadaverous graft in 14 patients. In 24 cases, a two-stage surgery was performed. The interval between the first- and the second-stage procedure ranged from 6 weeks up to 6 months, with the median of 62.4 days. During the evaluation, no difference was observed whether one-stage or two-stage surgery was performed, therefore this is not reflected in the overall evaluation. The clinical evaluation resulted in the following mean values when comparing the preoperative and final postoperative findings: The mean value of the IKDC subjective knee form score was 42 (30-62) preoperatively and increased to 77 (66-89) at 3 months. The values obtained at 6 months, 1 year and 3 years were 84 (73-93), 88 (79-100) and 89 (78-100), respectively. The mean value of the Lysholm score in the followedup study population was 63 preoperatively, which indicates a clearly poor result. The score rose to 71 (62-88) at 3 months, to 79 (67-92) at 6 months, to 89 (67-94) at 1 year, and at 3 years the mean score was again 89 (66-95). No serious complications were reported. CONCLUSIONS The results confirmed sufficient postoperative stability of the knee joint. In terms of function and pain perception the treatment was considered appropriate. No major complications occurred during surgeries. Based on the results, the authors foresee the patient s return to sports, at least at recreational level. Key words: anterior cruciate ligament, reconstruction, revision reconstruction, knee arthroscopy, instrumentarium.

[New Anterior Cruciate Ligament Reconstrucion Using Harmstring Tendon Grafts - Clinical Part]. / Nová metoda rekonstrukce predního zkrízeného vazu kolenního kloubu pomocí hamstringu ­ klinická cást.

PURPOSE OF THE STUDY The authors present the clinical use of the new instrumentation set for the anterior cruciate ligament (ACL) reconstruction using the hamstring tendons (HS). The positionning of the femoral tunnel and the fixation of the graft play an important role for the results of the surgery. The aim of the study was to confirm the proposed surgical technique and the methods of the graft fixation, especially from the point of view of the clinical midterm results at the evaluation up to eight years after the surgery. MATERIAL AND METHODS The clinical evaluation comprises 58 patients operated from 2007 to 2014 using the new instrumentation set. There were 9 men and 49 women included in the sample. The mean age was 34.6 years (range 18 - 58 yrs), namely 36.7 in women and 32.4 years in men. The evaluation was performed pre-opeatively and at 3 and 6 months, 1, 3, 5 and 8 years post-operatively. All the patients were followed based on the same criteria - clinical range of motion (ROM), stability of the knee - instrumentation Lachman test utilizing Rolimeter, subjective IKDC score and pain VAS scale for the harvesting site. The ocurrence and the rate of post-operative complications were monitored. RESULTS The integration and the ingrowth of the graft were achieved in all cases, the full ROM was gained as well, no pathological instability was observed. The fixation of the HS graft in the bone was confirmed by post-op X ray at 3 months after the surgery. The clinical evaluation showed the following mean differences in the pre-op and final post-op findings. The average preoperative laxity using the Lachmann test was 9.7 mm (range 6-12 mm), at 3 months 1.8 mm (1.4-2.1 mm), at 6 months 1.6 mm (1.2 - 2.2 mm), at 1 year 1.6 mm (1.1-2.3 mm), at 3 years the stability was 1.7 mm (1.2 mm-2.4 mm), at 5 years 2.3 mm (1.2-3.6 mm) and at 8 years after surgery it was 2.5 mm (1.2-3.9 mm). None of the patitents included in the study showed pathological instability that would be considered an indication for revision. In the evaluation of the subjective IKDC score, the pre-operative average was 56, with the range of 42-66, at 3 months post-operatively 79 (69-85), at 6 months 88 (74-92), at 1 year 95 (88-100), at 3 years 96 (89-100), at 5 years 94 (87-100), and at 8 years 92 (84-98). No severe complications were observed. CONCLUSIONS The method provided sufficient post-operative stability of the knee joint. Fixation of the femoral screw satisfied the demands laid on it. Regarding the pain perception, the method was considered positive, the level of pain involved in the procedure was low. No severe complications or technical mistakes occurred during the surgical procedures. The new instrumentation set developed for the ACL reconstruction offers an easy technique and comfortof use. Key words:anterior cruciate ligament, reconstruction, hamstrings, knee arthroscopy, instrumentation set.

Altered theta oscillations in resting EEG of fibromyalgia syndrome patients.

BACKGROUND: Fibromyalgia syndrome (FM) is a chronic pain disorder characterized by widespread pain, sleep disturbance, fatigue and cognitive/affective symptoms. Functional imaging studies have revealed that FM and other chronic pain syndromes can affect resting brain activity. This study utilized electroencephalographic (EEG) recordings to investigate the relative power of ongoing oscillatory activity in the resting brain. METHODS: A 64-channel EEG was recorded at rest in 19 female FM patients and 18 healthy, age-matched, control subjects. The Manual Tender Point Scale (MTPS) examination was performed to quantify tonic pain and tenderness on the day of testing along with measures of mood, arousal and fatigue. Oscillations in delta, theta, alpha, beta and gamma frequency bands were analysed using Standardised Low-Resolution Brain Electromagnetic Tomography to evaluate sources of spectral activity throughout the whole brain. RESULTS: FM patients exhibited greater pain, tiredness and tension on the day of testing relative to healthy control participants and augmented theta activity in prefrontal and anterior cingulate cortices. No significant differences were seen in other frequency bands. Augmented frontal theta activity in FM patients significantly correlated with measures of tenderness and mean tiredness scores. CONCLUSIONS: The findings indicate that alterations to resting-state oscillatory activity may relate to ongoing tonic pain and fatigue in FM, and manifest in brain regions relevant for cognitive-attentional aspects of pain processing and endogenous pain inhibition. Enhanced low-frequency oscillations were previously seen in FM and other chronic pain syndromes, and may relate to pathophysiological mechanisms for ongoing pain such as thalamocortical dysrhythmia. SIGNIFICANCE: Increased prefrontal theta activity may contribute to persistent pain in fibromyalgia or represent the outcome of prolonged symptoms. The findings point to the potential for therapeutic interventions aimed at normalizing neural oscillations, while further research utilizing quantitative analysis of resting EEG could benefit our understanding of fibromyalgia pathophysiology.

[New Technique of Anterior Cruciate Ligament Reconstruction Using Hamstrings - the Surgical Instrumentation Set]. / Nová metoda rekonstrukce predního zkrízeného vazu kolenního kloubu pomocí hamstringu ­ operacní instrumentárium.

PURPOSE OF THE STUDY The success rate of the anterior cruciate ligament (ACL) reconstruction depends on the fixation of the graft, the surgical technique and, of course, on the experience of the operating surgeon. The authors present the development of the construction of the new instrumentation set designed to manage the ACL lesions using the hamstring (HS) tendons. The study is divided into two parts, of which part one focuses on construction, methods and work with new instruments, while part two presents the outcomes of the surgery. MATERIAL AND METHODS Fixation of hamstring grafts depends, contrary to the union of bone blocks in the Bone-Tendon-Bone (BTB) graft and the bone tunnel, on the method of tendon graft fixation and compression inside the bone tunnel. The instrumentation set for ACL reconstruction is designed to be used for hamstring tendons (semitendon and gracilis) forming four strands of the prepared graft. The system was designed as the fixation of the graft using the femoral screw with eyelet and a press-fit fixation using a metal interference screw in tibia. The easiest and fastest option has proven to be the pulling of the screw with eyelet through the tibial tunnel and intra-articular space to the femoral canal, where fixation by screwing in is done. The exact position of the inserted screw is verified by the measuring gauge. The screw is pulled in by the long version of the femoral screwdriver and Kirschner wire passing through the middle of the screw with eyelet. The advantage of this system consists in the subsequent insertion of the interference screw by the same wire, which guarantees its exact positioning in the centre between the individual strands of the graft (thanks to the specific way of ligament preparation). The possibility of later tensioning of the graft by tightening the femoral screw is another advantage. DISCUSSION Compared to other methods using the HS tendons, the advantages of the described operative technique consist in the simplicity of the used instrumentation procedure. The technique of graft fixation inside the femoral canal is not suitable for bioabsorbable materials. It is offset by the fixation stability and the possibility of final graft tensioning. CONCLUSIONS The newly developed instrumentation set for ACL reconstruction is fit for purpose, easy as to the surgical technique, and it guarantees the logical sequence of surgical steps reducing surgical errors to minimum. The instrumentation set is userfriendly, easy to handle and, once the operating surgeon masters the surgical procedure, it allows to reduce the duration of the surgery to approximately 30 minutes. There were no major complications or technical errors reported during the surgical procedures using these instrumentation set. Key words: anterior cruciate ligament - reconstruction - instrumentation set - knee arthroscopy.

[Rare Dorsal Traumatic Sternoclavicular Joint Dislocation in a 14-Year-Old Patient - a Case Report]. / Raritní dorzální traumatická luxace sternoklavikulárního kloubu u ctrnáctiletého pacienta ­ kazuistika.

We report a case of a 14-year-old patient with rare dorsal sternoclavicular dislocation caused by a sports injury. The patient was admitted to our department for further investigation and treatment. After a series of examinations, an open reduction and fixation using K-wires was used as a treatment modality. A satisfactory outcome was achieved, the patient returned to full sports activity 3 months after the surgery, with no limitations of movement. The necessity of early diagnosis and treatment options of this rare injury has been discussed. Key words: sternoclavicular joint, dorsal dislocation, open reduction.

[Treatment of pelvic avulsion fractures in children and adolescents]. / Lécba avulzních zlomenin v oblasti pánve a kycle u detí a dospívajících.

INTRODUCTION: Paediatric avulsion fractures of the pelvis and hip joint are rare injuries most commonly associated with a rapid muscle contraction of the respected apophysis, which is the weakest component of the growing skeleton. The chosen therapy option can be either conservative or surgical. METHODS: We present a cohort of 69 patients treated for an apophyseal avulsion fracture of the anterior superior / inferior iliac spine, the lesser and greater trochanters iliac crest and the ischial tubercle. We compared the treatment outcomes, treatment time, need for immobilisation, and complications of conservative vs. surgical treatment. RESULTS: The mean time to mobilisation was 24.5 days in the conservative and 8.5 days in the surgical group of patients. In the group of surgically treated patients, healing signs were observed as early as in week 6. As of month 4, no difference was observed between the groups in terms of the clinical and radiological outcomes. CONCLUSIONS: The treatment outcomes of both methods are comparable in the long term. Surgery is indicated in dislocations exceeding 1 cm. Faster recovery and return to sports activities is the main advantage of the surgical treatment method. Disadvantages include the necessity of general anaesthesia as well as the risk of infection and the need of the osteosynthetic material removal. The choice of the treatment method remains individual depending on the type of injury and habitual practice of the centre.Key words: avulsion fracture - child - pelvis - treatment - outcome.

[Anterior Superior and Anterior Interior Iliac Spine Fractures. Comparison of the Results of Conservative and Surgical Treatment]. / Porovnání výsledku konzervativní a operacní lécby zlomenin spina iliaca anterior superior a spina iliaca anterior inferior u detí a dospívajících.

PURPOSE OF THE STUDY: Avulsion fractures of the anterior superior iliac spine (ASIS) and anterior inferior iliac spine (AIIS) are rare injuries to the skeleton in children. They are most frequent in adolescent athletes, such as sprinters and long-distance runners, and football players. The authors present a group of patients treated at their department and compare the results of procedures used to manage different pelvic avulsion fractures. MATERIAL AND METHODS: Between 2005 and 2012, 38 patients (31 boys and seven girls) with an average age of 15.1 years (range, 4-17 years) were treated. Fourteen patients with minimally displaced fractures were treated conservatively, 24 patients with fractures displaced more than 1 cm underwent surgery. All patients had a standard rehabilitation protocol. Post-operative assessments included: the range of motion in the hip; X-ray at 6 weeks, 3 months and 1 year; duration of bed rest; return to previous activities; occurrence of complications (heterotopic ossification, infection, etc). RESULTS: All patients returned to the pre-injury level of sports activities. Recovery was faster and early rehabilitation was better tolerated in patients treated surgically (p = 0.03), particularly in those with AIIS avulsion fractures. Ambulation with partial weight bearing was possible on average at 7.2 days (range, 2-10 days) in surgically treated patients and at 24.1 days (18-27 days) in conservatively treated patients; the difference was statistically significant (p = 0.02). The range of motion markedly improved in surgically treated patients as early as at 6 weeks while, in conservatively treated patients, the comparable outcome was achieved at 3 months of follow-up (p = 0.02). The time necessary for radiographic evidence of fragment union as well as full recovery was comparable in both patient groups. No deep wound infection was recorded; minor heterotopic ossification was detected in five patients, but no further treatment during follow-up was required. CONCLUSIONS: Indications for surgical treatment are based on the degree of fragment displacement and the patient's demands for sports activities. Although long-term outcomes of both operative and conservative procedures are comparable, the patients treated surgically show faster recovery and need a shorter time of immobilisation. However, removal of osteosynthesis material may be associated with some risk of complications.

Cerebral activations during viewing of food stimuli in adult patients with acquired structural hypothalamic damage: a functional neuroimaging study.

BACKGROUND/OBJECTIVES: Obesity is common following hypothalamic damage due to tumours. Homeostatic and non-homeostatic brain centres control appetite and energy balance but their interaction in the presence of hypothalamic damage remains unknown. We hypothesized that abnormal appetite in obese patients with hypothalamic damage results from aberrant brain processing of food stimuli. We sought to establish differences in activation of brain food motivation and reward neurocircuitry in patients with hypothalamic obesity (HO) compared with patients with hypothalamic damage whose weight had remained stable. SUBJECTS/METHODS: In a cross-sectional study at a University Clinical Research Centre, we studied 9 patients with HO, 10 age-matched obese controls, 7 patients who remained weight-stable following hypothalamic insult (HWS) and 10 non-obese controls. Functional magnetic resonance imaging was performed in the fasted state, 1 h and 3 h after a test meal, while subjects were presented with images of high-calorie foods, low-calorie foods and non-food objects. Insulin, glucagon-like peptide-1, Peptide YY and ghrelin were measured throughout the experiment, and appetite ratings were recorded. RESULTS: Mean neural activation in the posterior insula and lingual gyrus (brain areas linked to food motivation and reward value of food) in HWS were significantly lower than in the other three groups (P=0.001). A significant negative correlation was found between insulin levels and posterior insula activation (P=0.002). CONCLUSIONS: Neural pathways associated with food motivation and reward-related behaviour, and the influence of insulin on their activation may be involved in the pathophysiology of HO.

Modulation of pain by emotional sounds: a laser-evoked potential study.

BACKGROUND: Previous studies have shown increases in experimental pain during induction of a negative emotion with visual stimuli, verbal statements or unpleasant odours. The goal of the present study was to analyse the spatio-temporal activation patterns underlying pain augmentation during negative emotional sounds. METHODS: Negative (e.g., crying), positive (e.g., laughter) and neutral (e.g., distant traffic) sound samples of 4 s duration were presented while noxious laser stimuli were administered to the dorsum of the right hand in 16 healthy participants. The electroencephalographic laser-evoked potentials (LEPs) were modelled using six equivalent source dipoles located in the left and right fronto-opercular/anterior-insular cortex, left parietal operculum, left primary somatosensory cortex, medial parietal cortex and left medial temporal cortex. RESULTS: Negative emotional sounds were associated with stronger pain than neutral or positive sounds. The source activity in the left medial temporal cortex, purportedly involving hippocampal formation, in the epoch 294-330 ms was greater during negative than neutral or positive sounds. In the left fronto-opercular/anterior-insular cortex, negative sounds failed to show the positive potential component at around 260 ms that was observed during positive and especially during neutral sounds. CONCLUSIONS: Results suggest increased input of pain-related information into the hippocampal formation when listening to negative emotional sounds, which may in turn facilitate temporal binding between representations of noxious and other behaviourally relevant stimuli, and perhaps associative learning. Absence of the positive potential component fronto-opercular/anterior-insular cortex during negative sounds points to a slow attentional disengagement from pain and increased awareness of the painful stimulus.

Cortical oscillatory changes during warming and heating in humans.

Warmth and heat are registered by different types of cutaneous receptors. To disentangle the cortical activation patterns of warming and heating, we analyzed the temporal evolution of the electroencephalographic 10 and 20 Hz oscillations with the time resolution of hundreds of milliseconds. Sixty heat (from 32 to 50.5 degrees C, rate of change 6 degrees C/s) and warm (from 32 to 42 degrees C, 6 degrees C/s) stimuli were applied on the right thenar using contact thermode. EEG was recorded from 111 scalp electrodes in 12 healthy subjects, and analyzed using event-related desynchronization and low-resolution electromagnetic tomography methods. During warming, the amplitudes of 10 and 20 Hz oscillations over the contralateral primary sensorimotor (SI/MI) and premotor cortices decreased, and the amplitude of 20 Hz oscillations in the anterior cingulate and ipsilateral premotor cortex increased. Heating was associated with additional profound amplitude decreases of 10 and 20 Hz oscillations over SI/MI and premotor cortex, and by amplitude increase of 20 Hz oscillations originating in the posterior cingulate cortex. Results suggest biphasic amplitude changes of the cortical oscillations during ramp increase of temperature attributable to the periods of warming and heating. The amplitude decreases of 10 and 20 Hz oscillations in SI/MI and premotor cortex possibly aid in preparation of motor withdrawal reaction in an event that temperature should reach intolerable pain. Synchronization of the 20 Hz oscillations in the anterior and especially in the posterior cingulate cortex may aid suppression of unwanted movements.

Interaction of tactile input in the human primary and secondary somatosensory cortex--a magnetoencephalographic study.

Interaction of simultaneous tactile input at two finger sites in primary (SI) and secondary somatosensory cortex (SII) was studied by whole-head magnetoencephalography. Short pressure pulses were delivered to fingers of the right and left hand at an interstimulus interval of 1.6 s. The first phalanx of the left digit 1 and four other sites were stimulated either separately or simultaneously. We compared four sites with increasing distance: the second phalanx of left digit 1, left digit 5, and digits 1 and 5 of the right hand. The temporal evolution of source activity in the contralateral SI and bilateral SII was calculated using spatiotemporal source analysis. Interaction was assessed by comparing the source activity during simultaneous stimulation with the sum of the source activities elicited by separate stimulation. Significant suppressive interaction was observed in contralateral SI only for stimuli at the same hand, decreasing with distance. In SII, all digits of the same and the opposite hand interacted significantly with left digit 1. When stimulating bilaterally, SII source waveforms closely resembled the time course of the response to separate stimulation of the opposite hand. Thus, in bilateral simultaneous stimulation, the contralateral input arriving first in SII appeared to inhibit the later ipsilateral input. Similarly, the separate response to input at two unilateral finger sites which arrived slightly earlier in SII dominated the simultaneous response. Our results confirm previous findings of considerable overlap in the cortical hand representation in SII and illustrate hemispheric specialization to contralateral input when simultaneous stimuli occur bilaterally.

The electroencephalographic beta synchronization following extension and flexion finger movements in humans.

The cortical post-movement beta synchronization (PMBS) following brisk extension-flexion and flexion-extension movements of the right index finger was analyzed in twelve right-handed subjects using electroencephalographic recordings. The amplitude of PMBS over the contralateral sensorimotor area was enhanced and the focus of PMBS was widespread when finger flexion was the last movement. The results suggest that finger extension and flexion movements induce unequal beta synchronization over the contralateral M1 area possibly due to different complexity of the neuronal networks controlling these movements.

Oscillatory cortical activity and movement-related potentials in proximal and distal movements.

OBJECTIVES: Event-related desynchronization (ERD) of alpha- and beta-rhythms, the post-movement beta-synchronization and the cortical movement-related potentials were analyzed in distal (finger) and proximal (shoulder) movements. METHODS: EEG was recorded in 7 healthy right-handed men using a 59-channel whole-head EEG system while subjects performed self-paced movements. RESULTS: The amplitude of the Bereitschaftspotential (BP) was greater over the central midline area and smaller over the contralateral sensorimotor hand area in shoulder than in finger movements. The maximal alpha- and beta-ERD was localized at parietal electrodes in shoulder movements and over the left and right sensorimotor hand area in finger movements. The post-movement beta-ERS was greater in shoulder than in finger movements, especially at the electrode located 3.5 cm left of the central midline electrode. A significant correlation between the slope of the terminal portion of the BP (negative slope) and amplitude of the post-movement beta-synchronization was observed in shoulder but not in finger movements. CONCLUSIONS: Enhancement of BP over the central midline electrode suggests increased activation of the supplementary motor area in proximal movements. The spatial distribution of the alpha- and beta-ERD and of the post-movement beta-ERS shows topographic differences which may refer to the somatotopic organization of the primary sensorimotor cortex with shoulder representation medial to hand and fingers. The correlation between the negative slope and the post-movement beta-ERS in proximal movements supports the view that the brief post-movement inhibition over the motor cortical area is related to the pre-movement activation of that area.

Lateralization of movement-related potentials and the size of corpus callosum.

Using structural MRI and whole-head EEG recordings, we analyzed the correlations between the anatomical parameters of the corpus callosum and the hemispheric distribution of the cortical movement-related potentials during right finger and shoulder movements in nine right-handed men. Statistically significant correlation was found only in finger movements. A relatively large genu and the anterior part of the truncus of the corpus callosum correlated with enhanced pre-movement EEG potential over the ipsilateral M1/S1 area. The lateralization of the movement-related potentials correlates with the size of those callosal regions which connect the homologous areas of the primary sensorimotor and frontal cortices.

Spatial EEG synchronisation over sensorimotor hand areas in brisk and slow self-paced index finger movements.

The changes of spatial EEG synchronisation during brisk and slow voluntary self-paced movements of the right and left index finger were analysed in 12 right-handed and 11 left-handed subjects. EEG was recorded from the left and right sensorimotor area using 24 closely spaced electrodes. A novel measure of spatial EEG synchronisation, omega-complexity, was computed separately for the left and right sensorimotor area in 64 overlapping one-second epochs representing 4.5 s of the pre-movement and 3.5 s of the post-movement period. Omega-complexity was higher, hence spatial synchronisation was lower, in slow than in brisk movements, especially in the right-handed. A sustained increase of omega-complexity was observed during execution of a slow movement. A decrease of omega-complexity which was often associated with a brief burst of spatially synchronised 10-Hz oscillations occurred at the onset of extensor muscle contraction. We suggest that increased spatial EEG synchronisation at movement onset may prevent "spillover" of excitation from the sensorimotor hand area to other cortical regions. During movement, the cortical neuronal assemblies subserve distinct, specialised functions manifesting in increased omega-complexity.

Cardiac response induced by voluntary self-paced finger movement.

Cardiac responses induced by slow and brisk voluntary self-paced index finger movements of the dominant and non-dominant hand were investigated in a group of 12 right-handed subjects. Since subjects synchronised movement and respiration, initiating movement preferably during inspiration, a novel method of evaluating the movement-induced cardiac response was used. This method allows one to distinguish the differential effects on the cardiac response due to movement and respiration. The effect of type of movements (slow vs. brisk) and hand (right vs. left) were analysed. Slow movements induced a monophasic cardiac response, consisting of cardiac deceleration preceding and accompanying movement. Brisk movements induced a biphasic cardiac response, consisting of preparatory deceleration followed by slight post-movement cardiac acceleration. Hand-dominance did not influence the movement-induced cardiac response. The results suggest that neocortical structures involved in planning and execution of voluntary movement impinge upon brainstem cardiovascular nuclei. Vagal cardiac outflow is affected and gives rise to movement-induced changes in cardiac chronotropism.

The effects of external load on movement-related changes of the sensorimotor EEG rhythms.

The effects of external load opposing brisk voluntary extension of the right index finger on the EEG rhythms in the left and right sensorimotor hand area were studied in 13 right-handed subjects. Four levels of external loads corresponding to the weights of 0 g (no load), 30 g, 80 g and 130 g were used. The effects of external load on EEG rhythms were the following: (i) prior to movement, the desynchronisation of beta-rhythms (18-25 Hz) over the contralateral sensorimotor area was greater under the two largest loads as compared to the 0 g load. However, beta-desynchronisation at ipsilateral electrodes was larger under the 80 g load than under the 130 g load, presumably due to a transcallosally mediated inhibition exerted by the highly excited contralateral motor area; (ii) the mu-rhythm desynchronisation continued over both hemispheres for about 0.3-0.4 s after movement and the largest load was accompanied by the longest mu-rhythm desynchronisation; (iii) the post-movement beta-synchronisation was also longer under the heaviest load (130 g) as compared to the no-load condition (0 g), especially in subjects who prolonged their total movement time under the heaviest load. The results show that (i) the movement-related desynchronisation and synchronisation of sensorimotor EEG rhythms is influenced by external load opposing finger movement, and (ii) the effects of external load differ for the mu- and beta-rhythms.

On the existence of different types of central beta rhythms below 30 Hz.

EEGs were recorded from sensorimotor areas of 12 subjects performing unilateral self-paced brisk and slow finger movements. Two different beta components were found below 30 Hz: (i) One component, at about twice the frequency of the mu rhythm, showed desynchronization in parallel with the mu rhythm starting at about 2 s prior to movement. Measurements of bicoherence have shown that this beta component can be non-linearly related to the arch-shaped mu rhythm. (ii) Another beta component started to desynchronize about 1 s prior to movement, recovered very fast and displayed a pronounced post-movement beta synchronization (PMBS) within the first second after movement-offset. This PMBS was found in the frequency band between 12 and 26 Hz. The average percentage power increase at contralateral sensorimotor area was 232% (SD = 82%) for brisk and 265% (SD = 102%) for slow movements. The PMBS was of contralateral dominance and is interpreted as a correlate of active inhibition or idling of the primary motor area following movement execution.