No abstract

Magnetoencephalographic (MEG) studies have revealed enhancement of neural activity of the N1m response of auditory evoked fields in long-term trained musicians, reflecting neuroplastic modification of the representation of the auditory cortex. In contrast, the amplitude of the P2 response of auditory evoked potentials is modified by musical experience, with no alteration of N1. Here, we performed a comprehensive MEG study using stimulation of successive musical-instrument tones to examine how the neural activities of different MEG responses are modified in long-term experienced musicians who commenced musical lessons at ages of ϳ5 years and had continued to practice. The dipole moment of the P2m response occurring at 160 -180 ms was significantly enlarged in musicians compared with that in individuals who had not received musical lessons. The enlargement was found for the dipole moment of N1m occurring at 100 -120 ms in a restricted condition but not for the moment of P1m at 50 -60 ms. Furthermore, the dipole moment of P2m for successive stimuli, normalized by the moment for the first stimulus, was significantly larger for chord tones than single tones and was significantly larger in the musicians than controls. These results suggest that the P2m response is susceptible to be modified by musical training in a period of neural maturation, with a short refractory period of neural activity for the auditory input of composite tones. The P2m activity may be specialized to the processing of multifrequency sounds, such as musical timbre consisting of abundant harmonics.

No abstract

No abstract

The evaluation of the cumulative distribution function of a multivariate normal distribution is considered. The multivariate normal distribution can have any positive definite correlation matrix and any mean vector. The approach taken has two stages. In the first stage, it is shown how non-centred orthoscheme probabilities can be evaluated by using a recursive integration method. In the second stage, some ideas of Schläfli and Abrahamson are extended to show that any non-centred orthant probability can be expressed as differences between at most ("m" - 1)! non-centred orthoscheme probabilities. This approach allows an accurate evaluation of many multivariate normal probabilities which have important applications in statistical practice. Copyright 2003 Royal Statistical Society.

We analyze the performance of multiple input/multiple output (MIMO) communications systems employing spatial multiplexing and zero-forcing detection (ZF). The distribution of the ZF signal-to-noise ratio (SNR) is characterized when either the intended stream or interfering streams experience Rician fading, and when the fading may be correlated on the transmit side. Previously, exact ZF analysis based on a wellknown SNR expression has been hindered by the noncentrality of the Wishart distribution involved. In addition, approximation with a central-Wishart distribution has not proved consistently accurate. In contrast, the following exact ZF study proceeds from a lesser-known SNR expression that separates the intended and interfering channel-gain vectors. By first conditioning on, and then averaging over the interference, the ZF SNR distribution for Rician-Rayleigh fading is shown to be an infinite linear combination of gamma distributions. On the other hand, for Rayleigh-Rician fading, the ZF SNR is shown to be gammadistributed. Based on the SNR distribution, we derive new series expressions for the ZF average error probability, outage probability, and ergodic capacity. Numerical results confirm the accuracy of our new expressions, and reveal effects of interference and channel statistics on performance.

Reproductive isolation that initiates speciation is likely caused by incompatibility among multiple loci in organisms belonging to genetically diverging populations. Laboratory C57BL/6J mice, which predominantly originated from Mus musculus domesticus, and a MSM/Ms strain derived from Japanese wild mice (M. m. molossinus, genetically close to M. m. musculus) are reproductively isolated. Their F 1 hybrids are fertile, but successive intercrosses result in sterility. A consomic strain, C57BL/6J-ChrX MSM , which carries the X chromosome of MSM/Ms in the C57BL/6J background, shows male sterility, suggesting a genetic incompatibility of the MSM/Ms X chromosome and other C57BL/6J chromosome(s). In this study, we conducted genomewide linkage analysis and subsequent QTL analysis using the sperm shape anomaly that is the major cause of the sterility of the C57BL/6J-ChrX MSM males. These analyses successfully detected significant QTL on chromosomes 1 and 11 that interact with the X chromosome. The introduction of MSM/Ms chromosomes 1 and 11 into the C57BL/6J-ChrX MSM background failed to restore the sperm-head shape, but did partially restore fertility. This result suggests that this genetic interaction may play a crucial role in the reproductive isolation between the two strains. A detailed analysis of the male sterility by intracytoplasmic sperm injection and zona-free in vitro fertilization demonstrated that the C57BL/6J-ChrX MSM spermatozoa have a defect in penetration through the zona pellucida of eggs.

No abstract