Interaural level difference (ILD) is one of the basic binaural clues in the spatial localization of a sound source. Due to the acoustic shadow cast by the head, a sound source out of the medial plane results in an increased sound level at the nearer ear and a decreased level at the distant ear. In the mammalian auditory brainstem, the ILD is processed by a neuronal circuit of binaural neurons in the lateral superior olive (LSO). These neurons receive major excitatory projections from the ipsilateral side and major inhibitory projections from the contralateral side. As the sound level is encoded predominantly by the neuronal discharge rate, the principal function of LSO neurons is to estimate and encode the difference between the discharge rates of the excitatory and inhibitory inputs. Two general mechanisms of this operation are biologically plausible: (1) subtraction of firing rates integrated over longer time intervals, and (2) detection of coincidence of individual spikes within shorter time intervals. However, the exact mechanism of ILD evaluation is not known. Furthermore, given the stochastic nature of neuronal activity, it is not clear how the circuit achieves the remarkable precision of ILD assessment observed experimentally. We employ a probabilistic model and complementary computer simulations to investigate whether the two general mechanisms are capable of the desired performance. Introducing the concept of an ideal observer, we determine the theoretical ILD accuracy expressed by means of the just-noticeable difference (JND) in dependence on the statistics of the interacting spike trains, the overall firing rate, detection time, the number of converging fibers, and on the neural mechanism itself. We demonstrate that the JNDs rely on the precision of spike timing; however, with an appropriate parameter setting, the lowest theoretical values are similar or better than the experimental values. Furthermore, a mechanism based on excitatory and inhibitory coincidence detection may give better results than the subtraction of firing rates. This article is part of a Special Issue entitled Neural Coding 2012.

• Klíčová slova
• AN, Binaural hearing, CD, CN, CV, Coincidence detection, FF, Fano factor, ILD, ISI, ITD, Ideal observer, Interaural level difference, JND, Just-noticeable difference, LSO, MSO, Neuronal arithmetic, RLF, SFR, Sound localization, Subtraction of firing rate, auditory nerve, cochlear nucleus, coefficient of variation, coincidence detection, interaural level difference, interaural time difference, interspike interval, just-noticeable difference, lateral superior olive, medial superior olive, rate-level function, subtraction of firing rates,
• MeSH
• akční potenciály MeSH
• lokalizace zvuku fyziologie   MeSH
• modely neurologické * MeSH
• neurony fyziologie   MeSH
• nucleus olivaris caudalis fyziologie   MeSH
• počítačová simulace MeSH
• Poissonovo rozdělení MeSH
• vnímání prostoru fyziologie   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

One of the most widely investigated functions of the brain is vision. Whereas special attention is often paid to motion detection and its modulation by attention, comparatively still little is known about the structural background of this function. We therefore, examined the white matter microstructural background of coherent motion detection. A random-dot kinematogram paradigm was used to measure the sensitivity of healthy individuals׳ to movement coherence. The potential correlation was investigated between the motion detection threshold and the white matter microstructure as measured by high angular resolution diffusion MRI. The Track Based Spatial Statistics method was used to address this correlation and probabilistic tractography to reveal the connection between identified regions. A significant positive correlation was found between the behavioural data and the local fractional anisotropy in the posterior part of the right superior frontal gyrus, the right juxta-cortical superior parietal lobule, the left parietal white matter, the left superior temporal gyrus and the left optic radiation. Probabilistic tractography identified pathways that are highly similar to the segregated attention networks, which have a crucial role in the paradigm. This study draws attention to the structural determinant of a behavioural function.

• Klíčová slova
• DTI, MRI, Motion detection, Vision, White matter microstructure,
• MeSH
• anizotropie MeSH
• bílá hmota anatomie a histologie   fyziologie   MeSH
• diferenční práh fyziologie   MeSH
• difuzní magnetická rezonance MeSH
• dospělí MeSH
• lidé MeSH
• mladý dospělý MeSH
• mozek anatomie a histologie   fyziologie   MeSH
• nervové dráhy anatomie a histologie   fyziologie   MeSH
• psychofyzika MeSH
• světelná stimulace MeSH
• teorie detekce signálu fyziologie   MeSH
• vnímání pohybu fyziologie   MeSH
• Check Tag
• dospělí MeSH
• lidé MeSH
• mladý dospělý MeSH
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Vibrotactile perception thresholds (VPT) at seven test frequencies (8-500 Hz) have been measured and evaluated among 170 male employees at a heavy engineering production workshop, 125 of them were at present, or in the past, exposed to hand-arm vibration. All participants were examined by a physician and none had symptoms of diseases or were exposed to other factors known to cause sensory neuropathies. VPTs [for the three lowest (8-32 Hz; non-Pacinian), for the four highest (63-500 Hz; Pacinian) and for all test frequencies together] and a sensitivity index (SI) has been individually graded in four (normal, slightly deteriorated, deteriorated and seriously deteriorated) and two (normal, abnormal) stages, respectively, and put in relation to individual exposure of vibration. The results do not show any clear relationship on an individual basis between vibration exposure and degraded vibrotactile perception. On a group basis, however, there is a clear tendency towards detoriorated VPTs when the study group is divided in exposure categories. The detorioration is most pronounced in the frequency range mediated by Pacinian corpuscles. In this range an approximately four-fold increase of relative risk for elevated VPT for those in the highest exposure category was observed compared to the non-exposed group. Corresponding relative risk estimate for SI is about 6. Therefore, the results suggest an existence of an exposure-response relationship.

• MeSH
• biologické modely MeSH
• časové faktory MeSH
• diferenční práh MeSH
• dospělí MeSH
• hmat fyziologie   MeSH
• lidé MeSH
• poranění z opakovaného přetěžování prevence a kontrola   MeSH
• pracovní expozice škodlivé účinky   analýza   MeSH
• prsty ruky fyziologie   MeSH
• riziko MeSH
• vibrace škodlivé účinky   MeSH
• Check Tag
• dospělí MeSH
• lidé MeSH
• mužské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

• MeSH
• diferenční práh MeSH
• dospělí MeSH
• lidé MeSH
• oční fixace MeSH
• plnění a analýza úkolů MeSH
• pohyby očí * MeSH
• pozornost * MeSH
• světelná stimulace MeSH
• světlo MeSH
• vnímání tvaru MeSH
• zraková percepce * MeSH
• zraková pole MeSH
• Check Tag
• dospělí MeSH
• lidé MeSH
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH

The vibration sensitivity of the skin at the ten fingertips was tested with 72 chain saw operators examined due to VWF-disease and compared with controls. The vibrotactile perception threshold (frequency f = 125 Hz, load p = 1.3 N) proved to be 3 to 5 times as high for the exposed group compared to controls. There was no correlation between vibration sensitivity and peripheral circulation found in cold provocation test. Two different testing instruments (pallaesthesiometer = vibrotactometer) showed significant differences in results probably due to different technical details of the methods. It may be concluded that a standardization of the instrumentation and method is necessary for testing the vibrotactile perception threshold as a part of the nervous function in a comparable manner.

• MeSH
• diferenční práh MeSH
• dospělí MeSH
• hmat * MeSH
• lesnictví * MeSH
• lidé středního věku MeSH
• lidé MeSH
• nemoci z povolání diagnóza   etiologie   MeSH
• prsty ruky fyziologie   MeSH
• senioři MeSH
• studie případů a kontrol MeSH
• úžinové syndromy diagnóza   etiologie   MeSH
• vibrace škodlivé účinky   MeSH
• Check Tag
• dospělí MeSH
• lidé středního věku MeSH
• lidé MeSH
• mužské pohlaví MeSH
• senioři MeSH
• Publikační typ
• časopisecké články MeSH
• srovnávací studie MeSH

The authors assessed the differences of the limen of interrupted sounds (sounds which last 500 ms, between which there are intervals of 200 ms) in healthy subjects and in patients with sensory neural and supracochlear hearing disorders. Essentially the results are consistent with those of Schorn and Fastl (2) and they suggest that patients with supracochlear hearing disorders are able to differentiate only much greater differences in intensity (more than 4 dB) between sounds, as compared with patients with sensory neural hearing disorders.

• MeSH
• audiometrie čistými tóny * MeSH
• audiometrie * MeSH
• diferenciální diagnóza MeSH
• diferenční práh MeSH
• lidé MeSH
• nádory mozku komplikace   MeSH
• percepční nedoslýchavost diagnóza   etiologie   MeSH
• vestibulární schwannom diagnóza   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• anglický abstrakt MeSH
• časopisecké články MeSH

This contribution presents the results of fundamental investigations of the suitability of measurements of vibration sensitivity threshold (pallesthesiometry) as a method for the assessment of vibration-induced nerve impairments. Sinusoidal vibration stimuli are applied at the fingertips of the subjects in this method. The sensitivity threshold of the subjects is determined similar like the hearing threshold in audiometry and is used as a measure for possibly existing nerve disorders. Laboratory and field experiments were carried out by means of a simple to serve and inexpensive pallesthesiometer. The test results proved the suitability of the pallesthesiometry for screening purposes in principle. Concentration and cooperation of the subjects as well as the suitable selection of the investigation frequencies according to the frequency content of the vibration exposure are of essential meaning for comparable and reliable measuring results. Furthermore the rest and vibration-free position of the hand and fingers during the measurement of the thresholds are important to avoid measurement falsifications. A most extensive standardization of the investigation methodology and of the measuring equipment as well as the establishment of normative values of the sensitivity thresholds for different age groups are necessary for a broad application of the pallesthesiometry in practice.

• MeSH
• časové faktory MeSH
• diferenční práh MeSH
• dospělí MeSH
• hmat * MeSH
• lidé MeSH
• nemoci periferního nervového systému diagnóza   etiologie   MeSH
• nemoci z povolání diagnóza   etiologie   MeSH
• prsty ruky fyziologie   MeSH
• referenční hodnoty MeSH
• reprodukovatelnost výsledků MeSH
• věkové faktory MeSH
• vibrace škodlivé účinky   MeSH
• Check Tag
• dospělí MeSH
• lidé MeSH
• mužské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• klinické zkoušky kontrolované MeSH
• klinické zkoušky MeSH

The effect of shock repetition rate on the temporary threshold shifts (TTSs) in vibrotactile perception at the fingers has been studied with shocks having exponential decays and hanning waveforms. The repetition rate of shocks delivered at the hand varied from 2 shocks per second up to 64 shocks per second. Subjects were exposed to vertical hand-transmitted repetitive shock vibration of equal energy contents. The magnitudes of the stimuli were adjusted to 2.8 ms-2 r.m.s. so that they were all equally severe according to current standards for assessing the severity of hand-transmitted vibration (e.g. International Standard 5349, 1986). It was found that the TTS in vibrotactile perception decreased with decreasing shock repetition rate for both waveforms. The relation between the TTS, the logarithm of exposure time, and the logarithm of the ratio between the frequency-weighted r.m.s. acceleration and the peak amplitude was described by the relation TTS = 16.1 + 3.9log10T + 17.9log10 (RMS/PEAK), where TTS is the temporary threshold shift (in decibels), T is the exposure time, and RMS is the frequency-weighted r.m.s. acceleration according to BS 6842 and ISO 5349, and PEAK is the peak amplitude of the frequency-weighted acceleration. This shows that current standards are not appropriate for the prediction of the changes in vibrotactile perception produced by shocks such as those on many hand-held percussive tools.

• MeSH
• analýza rozptylu MeSH
• biologické modely MeSH
• časové faktory MeSH
• diferenční práh MeSH
• dospělí MeSH
• hmat fyziologie   MeSH
• lidé MeSH
• lineární modely MeSH
• poranění z opakovaného přetěžování etiologie   patofyziologie   MeSH
• pracovní expozice škodlivé účinky   analýza   MeSH
• prsty ruky fyziologie   MeSH
• ruka fyziologie   MeSH
• síla ruky MeSH
• vibrace škodlivé účinky   MeSH
• zrychlení MeSH
• Check Tag
• dospělí MeSH
• lidé MeSH
• mužské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• klinické zkoušky MeSH
• randomizované kontrolované studie MeSH

As occupational physicians in the building industry, we observed among these workers a high frequency of vibration exposure, during different tasks. We intended to study vibration exposure effects on vibration perception thresholds measured by digital tactilometry in this population of construction workers. A cross-sectional field study was made, 405 subjects were examined; each of them answered a questionnaire, underwent a medical examination and performed a test measuring his vibration perception thresholds, 150 subjects constituted the reference group. A close relationship between age and thresholds among the non-exposed group was observed. A threshold normalization of age of study the 204 exposed subjects was applied. Two exposure indices allowing time dependency vibration exposure analysis were defined the present daily exposure and cumulated exposure. In the examined population, thresholds rise with the present daily exposure in hours per day for 125 Hertz, while no significant influence of cumulated exposure is apparent. It was also pointed out that subjects exposed more than one and a half hour per day have higher thresholds than reference subjects, even if they do not have any clinical neurological complaints. This results seems to indicate the infraclinical feature of the test. These results suggest that screening of hand-arm vibration exposed population should be developed using this method. As occupational physicians in the construction industry, practising in Paris and surrounding areas, the authors studied the relationship between neurological disorders measured by vibrotactile perception thresholds, and hand-arm vibration exposure, among workers. They present the results of a field study they led within their institute, in collaboration with the tested workers' firms, and with the financial participation of the French Ministry of Labour.

• MeSH
• analýza rozptylu MeSH
• časové faktory MeSH
• diferenční práh MeSH
• dospělí MeSH
• hmat * MeSH
• lidé MeSH
• poranění z opakovaného přetěžování epidemiologie   MeSH
• pracovní expozice škodlivé účinky   analýza   MeSH
• prsty ruky fyziologie   MeSH
• průřezové studie MeSH
• studie případů a kontrol MeSH
• věkové faktory MeSH
• vibrace škodlivé účinky   MeSH
• Check Tag
• dospělí MeSH
• lidé MeSH
• Publikační typ
• časopisecké články MeSH

The aim of this study was to evaluate the influence of exercise with the intensity progressively increasing from rest until maximal oxygen uptake (VO2max) on 2,3-DPG levels in red blood cells (RBC) in relation to the changes in the acid-base balance and plasma lactate concentration. Six healthy young men (age 22.5+/-1.5 years, VO2max 3.48+/-0.20 l/min) participated in this study. The subjects performed an incremental exercise test on a cycloergometer until exhaustion. Blood samples were tested for acid-base balance indices (pH, HCO3-, BE), plasma lactate and RBC 2,3-DPG concentration. Gas exchange variables were measured continuously breath-by-breath. In this paper we present data concerning 2,3-DPG, plasma lactate, pH, HCO3- and BE measured at rest, at the power output corresponding to the lactate threshold (PO LT), at the power output at maximal oxygen uptake (PO VO2max), as well as 5, 15 and 30 min after finishing the incremental test. Increase of power output above the lactate threshold to the PO VO2max was accompanied by a significant (p<0.01) increase of plasma lactate from 2.58+/-0.78 mmol/l to 10.22+/-3.04 mmol/l. This was also accompanied by a significant drop (p<0.01) in blood pH value from 7.352+/-0.025 at the PO LT to 7.294+/-0.041 at the PO VO2max. No significant changes of the RBC 2,3-DPG level were observed at any of the analysed stages of the exercise. The RBC 2,3-DPG level expressed in relation to the changes of haematocrit showed only minor changes during the exercise period and after 15 min of recovery vs. resting value (3.21+/-1.19). However, after 30 min of recovery, RBC 2,3-DPG decreased to the value of 2.32+/-1.19 micromol/ml. We conclude that, during an incremental test, no increase in RBC 2,3-DPG concentration is required to reach the maximal oxygen uptake level. Moreover, a rapid decrease in blood pH, developing during a single bout of exercise, is not a stimulus powerful enough to cause significant changes in the RBC 2,3-DPG level during short-term exercise.

• MeSH
• 2,3-difosfoglycerát krev   MeSH
• acidobazická rovnováha fyziologie   MeSH
• diferenční práh fyziologie   MeSH
• dospělí MeSH
• erytrocyty metabolismus   MeSH
• krev metabolismus   MeSH
• kyselina mléčná krev   MeSH
• lidé MeSH
• osmolární koncentrace MeSH
• spotřeba kyslíku fyziologie   MeSH
• zátěžový test * MeSH
• Check Tag
• dospělí MeSH
• lidé MeSH
• mužské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• 2,3-difosfoglycerát MeSH
• kyselina mléčná MeSH