Beneficial effects of word final stress in segmenting a new language: evidence from ERPs

Background

How do listeners manage to recognize words in an unfamiliar language? The physical continuity of the signal, in which real silent pauses between words are lacking, makes it a difficult task. However, there are multiple cues that can be exploited to localize word boundaries and to segment the acoustic signal. In the present study, word-stress was manipulated with statistical information and placed in different syllables within trisyllabic nonsense words to explore the result of the combination of the cues in an online word segmentation task.

Results

The behavioral results showed that words were segmented better when stress was placed on the final syllables than when it was placed on the middle or first syllable. The electrophysiological results showed an increase in the amplitude of the P2 component, which seemed to be sensitive to word-stress and its location within words.

Conclusion

The results demonstrated that listeners can integrate specific prosodic and distributional cues when segmenting speech. An ERP component related to word-stress cues was identified: stressed syllables elicited larger amplitudes in the P2 component than unstressed ones.

     

Effect of visual target blurring on accommodation under distance viewing

Purpose

To examine the effect of visual target blurring on accommodation.

Methods

We evaluated the objective refraction values when the visual target (asterisk; 8°) was changed from the state without Gaussian blur (15 s) to the state with Gaussian blur adapted [0(without blur)?→?10, 0?→?50, 0?→?100: 15 s each].

Results

In Gaussian blur 10, when blurring of the target occurred, refraction value did not change significantly. In Gaussian blur 50 and 100, when blurring of the target occurred, the refraction value became significantly myopic.

Conclusion

Blurring of the distant visual target results in intervention of accommodation.

     

Mapping the brain's orchestration during speech comprehension: task-specific facilitation of regional synchrony in neural networks

Background

How does the brain convert sounds and phonemes into comprehensible speech? In the present magnetoencephalographic study we examined the hypothesis that the coherence of electromagnetic oscillatory activity within and across brain areas indicates neurophysiological processes linked to speech comprehension.

Results

Amplitude-modulated (sinusoidal 41.5 Hz) auditory verbal and nonverbal stimuli served to drive steady-state oscillations in neural networks involved in speech comprehension. Stimuli were presented to 12 subjects in the following conditions (a) an incomprehensible string of words, (b) the same string of words after being introduced as a comprehensible sentence by proper articulation, and (c) nonverbal stimulations that included a 600-Hz tone, a scale, and a melody. Coherence, defined as correlated activation of magnetic steady state fields across brain areas and measured as simultaneous activation of current dipoles in source space (Minimum-Norm-Estimates), increased within left- temporal-posterior areas when the sound string was perceived as a comprehensible sentence. Intra-hemispheric coherence was larger within the left than the right hemisphere for the sentence (condition (b) relative to all other conditions), and tended to be larger within the right than the left hemisphere for nonverbal stimuli (condition (c), tone and melody relative to the other conditions), leading to a more pronounced hemispheric asymmetry for nonverbal than verbal material.

Conclusions

We conclude that coherent neuronal network activity may index encoding of verbal information on the sentence level and can be used as a tool to investigate auditory speech comprehension.

     

Mathematical modelling and numerical simulation of the morphological development of neurons

Background

The morphological development of neurons is a very complex process involving both genetic and environmental components. Mathematical modelling and numerical simulation are valuable tools in helping us unravel particular aspects of how individual neurons grow their characteristic morphologies and eventually form appropriate networks with each other.

Methods

A variety of mathematical models that consider (1) neurite initiation (2) neurite elongation (3) axon pathfinding, and (4) neurite branching and dendritic shape formation are reviewed. The different mathematical techniques employed are also described.

Results

Some comparison of modelling results with experimental data is made. A critique of different modelling techniques is given, leading to a proposal for a unified modelling environment for models of neuronal development.

Conclusion

A unified mathematical and numerical simulation framework should lead to an expansion of work on models of neuronal development, as has occurred with compartmental models of neuronal electrical activity.

     

Learning course adjustments during arm movements with reversed sensitivity derivatives

Background

To learn, a motor system needs to know its sensitivity derivatives, which quantify how its neural commands affect motor error. But are these derivatives themselves learned, or are they known solely innately? Here we test a recent theory that the brain's estimates of sensitivity derivatives are revisable based on sensory feedback. In its simplest form, the theory says that each control system has a single, adjustable estimate of its sensitivity derivatives which affects all aspects of its task, e.g. if you learn to reach to mirror-reversed targets then your revised estimate should reverse not only your initial aiming but also your online course adjustments when the target jumps in mid-movement.

Methods

Human subjects bent a joystick to move a cursor to a target on a computer screen, but the cursor's motion was reversed relative to the joystick's. The target jumped once during each movement. Subjects had up to 4000 trials to practice aiming and responding to target jumps.

Results

All subjects learned to reverse both initial aiming and course adjustments.

Conclusions

Our study confirms that sensitivity derivatives can be relearned. It is consistent with the idea of a single, all-purpose estimate of those derivatives; and it suggests that the estimate is a function of context, as one would expect given that the true sensitivity derivatives may vary with the state of the controlled system, the target, and the motor commands.

     

The temporal relationship between reduction of early imitative responses and the development of attention mechanisms

Background

To determine whether early imitative responses fade out following the maturation of attentional mechanisms, the relationship between primitive imitation behaviors and the development of attention was examined in 4-month-old infants. They were divided into high and low imitators, based on an index of imitation. The status of attention was assessed by studying inhibition of return (IOR). Nine-month-old infants were also tested to confirm the hypothesis.

Results

The IOR latency data replicate previous results that infants get faster to produce a covert shift of attention with increasing age. However, those 4-month-olds who showed less imitation had more rapid saccades to the cue before target presentation.

Conclusion

The cortical control of saccade planning appears to be related to an apparent drop in early imitation. We interpret the results as suggesting a relationship between the status of imitation and the neural development of attention-related eye movement.

     

Relationship between corneal and ocular higher order wavefront aberrations and age in children

Purpose

To evaluate the relationship between corneal and ocular higher order wavefront aberrations (HOAs) and age in young subjects aged 20 years or less.

Methods

Corneal and ocular HOAs of the right eyes of 87 normal subjects were measured using videokeratography and the Hartmann–Shack wavefront aberrometer (KR-9000PW; Topcon Corp., Tokyo, Japan). The HOAs were calculated using Zernike polynomials up to the sixth order. From the Zernike coefficients, the root mean squares (RMS) of coma and spherical aberration were calculated.

Results

Corneal spherical-like aberrations significantly correlated with age (r = 0.420, p < 0.001); however, coma-like aberrations and total HOAs did not significantly correlate with age. None of the ocular HOAs significantly correlated with age. In addition, a gender-wise comparison of the collected data showed that corneal and ocular HOAs did not significantly correlate with age.

Conclusion

In children, the corneal and ocular total HOAs did not vary with age. Compared to the previous reports in adults, we found fewer corneal and ocular HOAs in children.

     

Measuring information integration

Background

To understand the functioning of distributed networks such as the brain, it is important to characterize their ability to integrate information. The paper considers a measure based on effective information, a quantity capturing all causal interactions that can occur between two parts of a system.

Results

The capacity to integrate information, or Φ, is given by the minimum amount of effective information that can be exchanged between two complementary parts of a subset. It is shown that this measure can be used to identify the subsets of a system that can integrate information, or complexes. The analysis is applied to idealized neural systems that differ in the organization of their connections. The results indicate that Φ is maximized by having each element develop a different connection pattern with the rest of the complex (functional specialization) while ensuring that a large amount of information can be exchanged across any bipartition of the network (functional integration).

Conclusion

Based on this analysis, the connectional organization of certain neural architectures, such as the thalamocortical system, are well suited to information integration, while that of others, such as the cerebellum, are not, with significant functional consequences. The proposed analysis of information integration should be applicable to other systems and networks.

     

Relationship between central and peripheral corneal astigmatism in elderly patients

Purpose

We investigated the relationship between central and peripheral corneal astigmatism in elderly patients.

Methods

Seventy-six eyes of 76 elderly subjects (mean age?=?72.6?±?3.0 years) were included in the study. Corneal shape was evaluated using the Pentacam HR (Oculus, Wetzlark, Germany), which is comprised of a rotating Scheimpflug camera and a short-wavelength slit light. The power distribution map was selected and corneal astigmatism was calculated using front K-Readings in zones centered on the pupil. Analyzed zones were 2.0–6.0 mm in diameter.

Results

Corneal astigmatism decreased as diameter increased, similar to what was observed in eyes with with-the-rule astigmatism and against-the-rule astigmatism (ANOVA, p?<?0.01). This effect was more pronounced in eyes with a large central corneal astigmatism (Spearman’s rank-correlation coefficient test, r?=?0.51, p?<?0.01). There was no change as to axis of corneal astigmatism (ANOVA, p?=?0.98).

Conclusion

These results suggest that the relationship between central and peripheral corneal astigmatism should be taken into consideration to optimize vision when astigmatic correction is needed.

     

Power-law for axon diameters at branch point

Background

Axon calibers vary widely among different animals, neuron classes, and even within the same neuron. What determines the diameter of axon branches?

Results

We pursue the hypothesis that the axon caliber has evolved to minimize signal propagation delays, while keeping arbor volume to a minimum. For a general cost function, we show that the optimal diameters of mother and daughter branches at a bifurcation satisfy a power law. The derivation relies on the fact that the axon conduction speed scales as a power of axon diameter. Although available data are consistent with the law, there is a large spread in the data. Future experimental tests will determine whether this spread is due to biological variability or measurement error.

Conclusions

Minimization of arbor volume and signal propagation delay may have been an important factor in the evolution of the brain.

     

Enhancement of blood-tumor barrier permeability by Sar-[D-Phe8]des-Arg9BK,a metabolically resistant bradykinin B1 agonist,in a rat C6 glioma model

Background

While it is well known that bradykinin B2 agonists increase plasma protein extravasation (PPE) in brain tumors, the bradykinin B1 agonists tested thus far are unable to produce this effect. Here we examine the effect of the selective B1 agonist bradykinin (BK) Sar-[D-Phe8]des-Arg9BK (SAR), a compound resistant to enzymatic degradation with prolonged activity on PPE in the blood circulation in the C6 rat glioma model.

Results

SAR administration significantly enhanced PPE in C6 rat brain glioma compared to saline or BK (p < 0.01). Pre-administration of the bradykinin B1 antagonist [Leu8]-des-Arg (100 nmol/Kg) blocked the SAR-induced PPE in the tumor area.

Conclusions

Our data suggest that the B1 receptor modulates PPE in the blood tumor barrier of C6 glioma. A possible role for the use of SAR in the chemotherapy of gliomas deserves further study.

     

Context-dependent selection of visuomotor maps

Background

Behavior results from the integration of ongoing sensory signals and contextual information in various forms, such as past experience, expectations, current goals, etc. Thus, the response to a specific stimulus, say the ringing of a doorbell, varies depending on whether you are at home or in someone else's house. What is the neural basis of this flexibility? What mechanism is capable of selecting, in a context-dependent way an adequate response to a given stimulus? One possibility is based on a nonlinear neural representation in which context information regulates the gain of stimulus-evoked responses. Here I explore the properties of this mechanism.

Results

By means of three hypothetical visuomotor tasks, I study a class of neural network models in which any one of several possible stimulus-response maps or rules can be selected according to context. The underlying mechanism based on gain modulation has three key features: (1) modulating the sensory responses is equivalent to switching on or off different subpopulations of neurons, (2) context does not need to be represented continuously, although this is advantageous for generalization, and (3) context-dependent selection is independent of the discriminability of the stimuli. In all cases, the contextual cues can quickly turn on or off a sensory-motor map, effectively changing the functional connectivity between inputs and outputs in the networks.

Conclusions

The modulation of sensory-triggered activity by proprioceptive signals such as eye or head position is regarded as a general mechanism for performing coordinate transformations in vision. The present results generalize this mechanism to situations where the modulatory quantity and the input-output relationships that it selects are arbitrary. The model predicts that sensory responses that are nonlinearly modulated by arbitrary context signals should be found in behavioral situations that involve choosing or switching between multiple sensory-motor maps. Because any relevant circumstancial information can be part of the context, this mechanism may partly explain the complex and rich behavioral repertoire of higher organisms.

     

A role of melanin-concentrating hormone producing neurons in the central regulation of paradoxical sleep

Background

Peptidergic neurons containing the melanin-concentrating hormone (MCH) and the hypocretins (or orexins) are intermingled in the zona incerta, perifornical nucleus and lateral hypothalamic area. Both types of neurons have been implicated in the integrated regulation of energy homeostasis and body weight. Hypocretin neurons have also been involved in sleep-wake regulation and narcolepsy. We therefore sought to determine whether hypocretin and MCH neurons express Fos in association with enhanced paradoxical sleep (PS or REM sleep) during the rebound following PS deprivation. Next, we compared the effect of MCH and NaCl intracerebroventricular (ICV) administrations on sleep stage quantities to further determine whether MCH neurons play an active role in PS regulation.

Results

Here we show that the MCH but not the hypocretin neurons are strongly active during PS, evidenced through combined hypocretin, MCH, and Fos immunostainings in three groups of rats (PS Control, PS Deprived and PS Recovery rats). Further, we show that ICV administration of MCH induces a dose-dependant increase in PS (up to 200%) and slow wave sleep (up to 70%) quantities.

Conclusion

These results indicate that MCH is a powerful hypnogenic factor. MCH neurons might play a key role in the state of PS via their widespread projections in the central nervous system.

     

PKCε phosphorylation regulates the mitochondrial translocation of ATF2 in ischemia-induced neurodegeneration

Background

Global cerebral ischemia triggers neurodegeneration in the hippocampal CA1 region, but the mechanism of neuronal death remains elusive. The epsilon isoform of protein kinase C (PKCε) has recently been identified as a master switch that controls the nucleocytoplasmic trafficking of ATF2 and the survival of melanoma cells. It is of interest to assess the role of PKCε–ATF2 signaling in neurodegeneration.

Results

Phosphorylation of ATF2 at Thr-52 was reduced in the hippocampus of PKCε null mice, suggesting that ATF2 is a phosphorylation substrate of PKCε. PKCε protein concentrations were significantly reduced 4, 24, 48 and 72 h after transient global cerebral ischemia, resulting in translocation of nuclear ATF2 to the mitochondria. Degenerating neurons staining positively with Fluoro-Jade C exhibited cytoplasmic ATF2.

Conclusions

Our results support the hypothesis that PKCε regulates phosphorylation and nuclear sequestration of ATF2 in hippocampal neurons during ischemia-induced neurodegeneration.

     

Comparison of the responses of the chorda tympani and glossopharyngeal nerves to taste stimuli in C57BL/6J mice

Background

Recent progress in discernment of molecular pathways of taste transduction underscores the need for comprehensive phenotypic information for the understanding of the influence of genetic factors in taste. To obtain information that can be used as a base line for assessment of effects of genetic manipulations in mice taste, we have recorded the whole-nerve integrated responses to a wide array of taste stimuli in the chorda tympani (CT) and glossopharyngeal (NG) nerves, the two major taste nerves from the tongue.

Results

In C57BL/6J mice the responses in the two nerves were not the same. In general sweeteners gave larger responses in the CT than in the NG, while responses to bitter taste in the NG were larger. Thus the CT responses to cyanosuosan, fructose, NC00174, D-phenylalanline and sucrose at all concentrations were significantly larger than in the NG, whereas for acesulfame-K, L-proline, saccharin and SC45647 the differences were not significant. Among bitter compounds amiloride, atropine, cycloheximide, denatonium benzoate, L-phenylalanine, 6-n-propyl-2-thiouracil (PROP) and tetraethyl ammonium chloride (TEA) gave larger responses in the NG, while the responses to brucine, chloroquine, quinacrine, quinine hydrochloride (QHCl), sparteine and strychnine, known to be very bitter to humans, were not significantly larger in the NG than in the CT.

Conclusion

These data provide a comprehensive survey and comparison of the taste sensitivity of the normal C57BL/6J mouse against which the effects of manipulations of its gustatory system can be better assessed.

     

The effect of anesthetic dose on the motor response induced by low-intensity pulsed ultrasound stimulation

Background

Low-intensity pulsed ultrasound stimulation (LIPUS) has been proven to be a noninvasive method with high spatial resolution and deep penetration. Previous studies have qualitatively demonstrated that the electromyographic response caused by LIPUS in the mouse motor cortex is affected by the anesthetic state of the mice. However, the quantitative relationship between motor response and anesthetic dose remains unclear.

Results

Experimental results show that the success rate decreases stepwise as the isoflurane concentration/mouse weight ratio increases (ratios: [0.004%/g, 0.01%/g], success rate: ~?90%; [0.012%/g, 0.014%/g], ~?40%; [0.016%/g, 0.018%/g], ~?7%; 0.024%/g, 0). The latency and duration of EMG increase significantly when the ratio is more than 0.016%/g. Compared with that at ratios from 0.004 to 0.016%/g, normalized EMG amplitude decreases significantly at ratios of 0.018%/g and 0.020%/g.

Conclusions

Quantitative calculations indicate that the anesthetic dose has a significant regulatory effect on the motor response of mice during LIPUS. Our results have guiding significance for the selection of the anesthetic dose for LIPUS in mouse motor cortex experiments.

     

Qualitative and quantitative differences between taste buds of the rat and mouse

Background

Numerous electrophysiological, ultrastructural, and immunocytochemical studies on rodent taste buds have been carried out on rat taste buds. In recent years, however, the mouse has become the species of choice for molecular and other studies on sensory transduction in taste buds. Do rat and mouse taste buds have the same cell types, sensory transduction markers and synaptic proteins? In the present study we have used antisera directed against PLCβ2, α-gustducin, serotonin (5-HT), PGP 9.5 and synaptobrevin-2 to determine the percentages of taste cells expressing these markers in taste buds in both rodent species. We also determined the numbers of taste cells in the taste buds as well as taste bud volume.

Results

There are significant differences (p < 0.05) between mouse and rat taste buds in the percentages of taste cells displaying immunoreactivity for all five markers. Rat taste buds display significantly more immunoreactivity than mice for PLCβ2 (31.8% vs 19.6%), α-gustducin (18% vs 14.6%), and synaptobrevin-2 (31.2% vs 26.3%). Mice, however, have more cells that display immunoreactivity to 5-HT (15.9% vs 13.7%) and PGP 9.5 (14.3% vs 9.4%). Mouse taste buds contain an average of 85.8 taste cells vs 68.4 taste cells in rat taste buds. The average volume of a mouse taste bud (42,000 μm³) is smaller than a rat taste bud (64,200 μm³). The numerical density of taste cells in mouse circumvallate taste buds (2.1 cells/1000 μm³) is significantly higher than that in the rat (1.2 cells/1000 μm³).

Conclusion

These results suggest that rats and mice differ significantly in the percentages of taste cells expressing signaling molecules. We speculate that these observed dissimilarities may reflect differences in their gustatory processing.

     

Anatomical location of Macrophage Migration Inhibitory Factor in urogenital tissues,peripheral ganglia and lumbosacral spinal cord of the rat

Background

Previous work suggested that macrophage migration inhibitory factor (MIF) may be involved in bladder inflammation. Therefore, the location of MIF was determined immunohistochemically in the bladder, prostate, major pelvic ganglia, sympathetic chain, the L6-S1 dorsal root ganglia (DRG) and the lumbosacral spinal cord of the rat.

Results

In the pelvic organs, MIF immunostaining was prominent in the epithelia. MIF was widely present in neurons in the MPG and the sympathetic chain. Some of those neurons also co-localized tyrosine hydroxylase (TH). In the DRGs, some of the neurons that stained for MIF also stained for Substance P. In the lumbosacral spinal cord, MIF immunostaining was observed in the white mater, the dorsal horn, the intermediolateral region and in the area around the central canal. Many cells were intensely stained for MIF and glial fibrillary acidic protein (GFAP) suggesting they were glial cells. However, some cells in the lumbosacral dorsal horn were MIF positive, GFAP negative cells suggestive of neurons.

Conclusions

Therefore, MIF, a pro-inflammatory cytokine, is localized to pelvic organs and also in neurons of the peripheral and central nervous tissues that innervate those organs. Changes in MIF's expression at the end organ and at peripheral and central nervous system sites suggest that MIF is involved in pelvic viscera inflammation and may act at several levels to promote inflammatory changes.