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At least 163 records · Page 9Linked to original sources
PubMed2003

Using improved neural network model to analyze RSP, NOx and NO2 levels in urban air in Mong Kok, Hong Kong.

As the health impact of air pollutants existing in ambient addresses much attention in recent years, forecasting of air pollutant parameters becomes an important and popular topic in environmental science. Airborne pollution is a serious, and will be a major problem in Hong Kong within the next few years. In Hong Kong, Respirable Suspended Particulate (RSP) and Nitrogen Oxides NOx and NO2 are major air pollutants due to the dominant diesel fuel usage by public transportation and heavy vehicles. Hence, the investigation and prediction of the influence and the tendency of these pollutants are of significance to public and the city image. The multi-layer perceptron (MLP) neural network is regarded as a reliable and cost-effective method to achieve such tasks. The works presented here involve developing an improved neural network model, which combines the principal component analysis (PCA) technique and the radial basis function (RBF) network, and forecasting the pollutant levels and tendencies based in the recorded data. In the study, the PCA is firstly used to reduce and orthogonalize the original input variables (data), these treated variables are then used as new input vectors in RBF neural network model established for forecasting the pollutant tendencies. Comparing with the general neural network models, the proposed model possesses simpler network architecture, faster training speed, and more satisfactory predicting performance. This improved model is evaluated by using hourly time series of RSP, NOx and NO2 concentrations collected at Mong Kok Roadside Gaseous Monitory Station in Hong Kong during the year 2000. By comparing the predicted RSP. NOx and NO2 concentrations with the actual data of these pollutants recorded at the monitory station, the effectiveness of the proposed model has been proven. Therefore, in authors' opinion, the model presented in the paper is a potential tool in forecasting air quality parameters and has advantages over the traditional neural network methods.

Air Pollutants↗
PubMedDate not supplied

[Neurocyte reaction of the kinesthetic analyzer of rats to the action of vibration].

By neurohistological, morphometric and electron-microscopic methods the effect of vibration of 80 Hz applied at an acceleration of 8 m/sec2 on the nerve cell and conduction components of the kinesthetic analyzer was investigated. After a single exposure to vibration nerve cells of the sensorimotor cortex showed some changes. Exposure to vibration for as long as a week caused reactive changes in every structure of the kinesthetic analyzer investigated. After 1-month exposure the changes were more disseminated and became destructive, after 2-month exposure the process developed at a slower rate, and after 3-month exposure it remained at the same level. However, after 3-month exposure the morphological equivalent of compensatory-adaptive reactions was seen.

Animals↗
PubMedDate not supplied

[The role of the medial geniculate bodies in analyzing sounds].

Elaboration and manifestation of motor alimentary conditioned reflexes were studied after a lesion of medial geniculate bodies (MGB) in adult cats. No substantial disturbance were recorded of the capacity for pitch analysis. In the case of more extensive MGB lesions, there were some difficulties in the elaboration of tone differentiations but not in their achievement. Additional temporo-parietal cortical ablation drastically reduced the animals' capacity for anlysing sound frequencies and more profoundly disturbed their capacity for inhibitory reactions.

Animals↗
PubMedDate not supplied

[Effect of a dominant focus in the midbrain reticular formation on the functional state of the motor analyzer].

In chronic experiments on rabbits it was shown that after two-three stimulations of the midbrain reticular formation (stimulation frequency 200 cps, pulse duration 0.1-0.5 ms, voltage 1-3 V, stimulation duration 5 s) a dominant focus was formed in it, which led simultaneously to a statistically significant increase in the amplitude of evoked potential in the sensorimotor cerebral cortex and in motor reactions to afferent stimuli (light, sound). The state of increased excitability persisted for a long time (10-30 days depending on the number of stimulations of the reticular formation). Multiple stimulation of the reticular formation (5-12 times) led to creation of a pathological defensive dominant, manifested in a unitype series of legs movements in response to light and sound stimuli.

Animals↗
PubMed1985

A consideration of sensory factors involved in motor functions of the basal ganglia.

There is a sizeable literature concerning basal ganglia (BG) functioning that is based on data from experiments employing a method of analysis that is traditionally used with other motor areas. A brief review of this literature is presented and the following conclusion is reached: as compared to the success of traditional methodologies in elucidating the workings of other motor systems, their use in BG investigations has proven disappointing. A possible reason for the shortcomings of traditional analyses in BG research is discussed. The remainder of this review concerns an alternative approach to the study of the BG that follows from consideration of a variety of clinical and experimental findings. The literature suggests that sensory aspects of BG functioning must be taken into account to fully appreciate the role of this system in motor control. A review of the literature concerning the latter suggests two points: The BG function as sensory analyzer for motor systems. That is, the BG convert sensory data from a form that is receptor oriented to a form that is relevant for guiding movement. The BG ultimately affect movement by gating sensory inputs into other motor areas rather than by directly affecting these areas. This sensory-based model of BG functioning explains a number of apparent discrepancies in the literature. In addition, seemingly anomalous findings are reconciled with the overwhelming evidence that the BG are a motor system. In particular, the suggestions of a BG role in attention and cognition are viewed as being intrinsic rather than orthogonal to the role of the BG in movement.

Animals↗
PubMedDate not supplied

[Properties of nuclear and dispersed elements of the cortical end of the auditory analyzer according to total evoked potentials to sound].

In chronic experiments on cats short-latency evoked potentials (EPs) to clicks were recorded simultaneously in three cortical areas--auditory (nuclear elements of the cortical end of the auditory analyser) sensorimotor and visual ones (scattered auditory elements). EPs to above threshold clicks in the auditory area differed from EPs of non-auditory areas by a greater amplitude and relatively stable configuration. The EP threshold in the auditory area was lower and the increase in its amplitude throughout a rise in clicks' intensity far greater than in the non-auditory areas. The above difference in responses of nuclear elements in the primary auditory cortex and of scattered elements in non-auditory areas are considered as the sign of specificity of their functional organization, i. e. as the manifestation of the participation of auditory nuclear elements in a relatively delicate analysis of auditory stimuli and that of scattered ones--in a more simple and limited analysis.

Animals↗
PubMedDate not supplied

[Cortico-subcortical interrelationships in the visual analyzer system at various stages of ontogenesis].

The influence of a corticofugal volley produced by single electrical stimulation of the visual projection cortical zone on the neuronal activity of LGB was studied in non-anaesthetized rabbits aged from three to thirty-five days. A coincidence was found between the time of appearance of nonspecific inhibitory corticofugal influences on the spontaneous activity of LGB neurons and the emergence of the first phasic-specific responses of the neurones of this level to a visual stimulus. It has been shown that the sensory flow at the LGB level can be controlled by non-specific inhibitory corticofugal influences at early periods of postnatal development. The appearance from the 15th day of life of specific responses to a corticofugal volley, including activation phases, leads to a greater complexity of the regulating Cortical influences on conduction of the afferent signal at the thalamic level. The data obtained are considered from the standpoint of integration of various levels of the visual analyser at different stages of ontogenesis.

Animals↗
PubMed1994

Brain stem integration of vocalization: role of the midbrain periaqueductal gray.

1. The contribution of the midbrain periaqueductal gray (PAG) to the central regulation of vocalization was investigated by analyzing the electromyographic (EMG) changes in respiratory, laryngeal, and oral muscles evoked by microinjection of D,L-homocysteic acid (DLH) in the PAG of unanesthetized, precollicular decerebrate cats. Moderate to large (6-40 nmol) doses of DLH evoked natural-sounding vocalization as well as increases in inspiratory depth and respiratory rate. 2. Two basic types of vocalization were evoked, each associated with a distinct and characteristic pattern of respiratory, laryngeal and oral EMG changes. Type A vocalization (voiced sounds such as howl/mew/growl) was characterized by excitation of the cricothyroid (CT) and thyro-arytenoid (TA) muscles, and inhibition of the posterior crico-arytenoid (PCA) muscle, whereas type B vocalization (unvoiced hiss sounds) was characterized by excitation of the PCA and TA muscles and no significant activation of the CT muscle. In addition, stronger expiratory (external oblique, internal oblique, internal intercostal) EMG increases were associated with type A responses, and larger increases in genioglossus and digastric muscle activity were associated with type B responses. 3. Microinjections of small doses of DLH (300 pmol-3 nmol), also evoked patterned changes in muscle activity (usually without audible vocalization) that, although of lower amplitude, were identical to those evoked by injections of moderate to large DLH doses. In no such experiments (175 sites) were individual muscles activated by small dose injections of DLH into the PAG. Further, type A vocalization/muscle patterns were evoked from PAG sites caudal to those at which type B vocalization/muscle patterns were evoked. 4. Considered together these results indicate: that the PAG contains topographically separable groups of neurons that coordinate laryngeal, respiratory, and oral muscle patterns characteristic of two fundamental types of vocalization and that the underlying PAG organization takes the form of a representation of muscle patterns, rather than individual muscles. 5. The patterns of EMG activity evoked by excitation of PAG neurons were strikingly similar to previously reported patterns of EMG activity characteristic of major phonatory categories in higher species, including humans (e.g., vowel phonation, voiceless consonant phonation). These findings raise the possibility that the sound production circuitry of the PAG could well be utilized by cortical and subcortical "language structures" to coordinate basic respiratory and laryngeal motor patterns that are necessary for speech.

Animals↗
PubMed2004

Developmental changes in the expression of somatostatin receptors (1-5) in the brain, hypothalamus, pituitary and spinal cord of the human fetus.

The actions of somatostatin (SST) in the nervous system are mediated by specific high affinity SST receptors (SSTR1-5). However, the role of this hormone and the distribution of its receptor subtypes have not yet been defined in neural structures of the human fetus. We have analyzed four neural tissues (CNS, hypothalamus, pituitary and spinal cord) from early to midgestation for the expression of five human SSTR mRNAs, using a reverse transcription-polymerase chain reaction and Southern blot approach. These fetal neural tissues all express mRNA for multiple SSTR subtypes from as early as 16 weeks of fetal life but the developmental patterns of expression vary considerably. Transcripts for SSTR1 and SSTR2A are the most widely distributed, being expressed in all four neural tissues. SSTR2A is often the earliest transcript to be detected (7.5 weeks in CNS). SSTR3 mRNA is confined to the pituitary, hypothalamus, and spinal cord. SSTR4 is expressed in fetal brain, hypothalamus and spinal cord but not pituitary. SSTR5 mRNA is detectable in the pituitary and spinal cord by 14-16 weeks of fetal life. This mapping of SSTR mRNA expression patterns in human fetal neural tissues is an important first step toward our goal of determining the role of SST in the nervous system during early stages in human development.

Aborted Fetus↗
PubMed2003

Neural networks for the coordination of the hands in time.

Without practice, bimanual movements can typically be performed either in phase or in antiphase. Complex temporal coordination, e.g., during movements at different frequencies with a noninteger ratio (polyrhythms), requires training. Here, we investigate the organization of the neural control systems for in-phase, antiphase, and polyrhythmic coordination using functional magnetic resonance imaging (fMRI). Brisk rhythmic tapping with the index fingers was used as a model behavior. We demonstrate different patterns of brain activity during in-phase and antiphase coordination. In-phase coordination was characterized by activation of the right anterior cerebellum and cingulate motor area (CMA). Antiphase coordination was accompanied by extensive fronto-parieto-temporal activations, including the supplementary motor area (SMA), the preSMA, and the bilateral inferior parietal gyri, premotor cortex, and superior temporal gyri. When contrasting polyrhythmic tapping with in-phase tapping, activity was seen in the same set of brain regions, and in the posterior cerebellum and the CMA. Antiphase and polyrhythmic coordination may thus to a large extent use common neural control circuitry. In a separate experiment, we analyzed the neural control of the rhythmic structure and the serial order of finger movements during polyrhythmic tapping. Polyrhythmic tapping was compared with an isochronous coordination pattern that retained the same serial order of finger movements as the polyrhythm. This experiment showed that the preSMA and the bilateral superior temporal gyri may be crucial for the rhythmic control of polyrhythmic tapping, while the cerebellum, the CMA, and the premotor cortices presumably are more involved in the ordinal control of the sequence of finger movements.

Adult↗
PubMed2001

Normal neurogenesis and scrapie pathogenesis in neural grafts lacking the prion protein homologue Doppel.

The agent that causes prion diseases is thought to be identical to PrPSc, a conformer of the normal prion protein PrPC. Recently a novel protein, termed Doppel (Dpl), was identified that shares significant biochemical and structural homology with PrPC. To investigate the function of Dpl in neurogenesis and in prion pathology, we generated embryonic stem (ES) cells harbouring a homozygous disruption of the Prnd gene that encodes Dpl. After in vitro differentiation and grafting into adult brains of PrPC-deficient Prnp0/0 mice, Dpl-deficient ES cell-derived grafts contained all neural lineages analyzed, including neurons and astrocytes. When Prnd-deficient neural tissue was inoculated with scrapie prions, typical features of prion pathology including spongiosis, gliosis and PrPSc accumulation, were observed. Therefore, Dpl is unlikely to exert a cell-autonomous function during neural differentiation and, in contrast to its homologue PrPC, is dispensable for prion disease progression and for generation of PrPSc.

Animals↗