The responses of 51 neurons in the lateral geniculate nucleus of the rabbit to substitution of colored stimuli different brightness and stimuli differing only in intensity were studied. Neurons in the geniculate nucle...
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The responses of 51 neurons in the lateral geniculate nucleus of the rabbit to substitution of colored stimuli different brightness and stimuli differing only in intensity were studied. Neurons in the geniculate nucleus, like neurons in the visual cortex, were found to respond with initial phasic discharges at 50-90 msec after stimulus substitution, the magnitudes of these responses correlating with the interstimulus differences;neurons also showed prolonged tonic responses in which the spike frequency depended on the intensity of the stimulus presented. Analysis of phasic responses allowed two groups of neurons to be identified: some were specialized to discriminate stimulus intensity only, while others were specialized to discriminate both the intensity and the color tone of the stimulus. Use of the magnitude of the early phasic discharge as a measure of the difference between stimuli yielded a sensory space for lateral geniculate nucleus neurons. The responses of neurons in the first group (44 cells, 86%) produced a two-dimensional achromatic space with two axes - brightness and darkness;this structure appeared independently of whether stimuli were of the same or different color tones. The phasic responses of neurons in the second group (seven of 51, 14%) generated a four-dimensional space with two color and two achromatic axes. The color and achromatic spaces of lateral geniculate nucleus neurons were analogous to the spaces previously identified for neurons in the rabbit visual cortex using the same stimulation conditions. The sensory spaces reconstructed on the basis of neuron phasic discharges essentially coincided with the spaces obtained from analysis of the N85 component of visual evoked potentials in rabbits, which provides support for the vector information coding principle in the visual analyzer. The tonic discharges of most lateral geniculate nucleus neurons correlated linearly with changes in stimulus intensity and can be regarded as reflecting a pre-
To distinguish chatter gestation, chatter recognition based on hybrid SOM/DHMM is proposed for dynamic Patterns of chatter gestation in cutting process. At first FFT features are extracted from the vibration signal of...
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ISBN:
(纸本)9781424410651
To distinguish chatter gestation, chatter recognition based on hybrid SOM/DHMM is proposed for dynamic Patterns of chatter gestation in cutting process. At first FFT features are extracted from the vibration signal of cutting process, then FFT vectors are presorted and coded into code book of integer numbers by SOM(Self-Organizing Feature Map), and these code books are introduced to DHMM (Discrete Hidden Markov Models), for machine learning and classification. Finally the results of chatter gestation recognition and chatter prediction experiments are presented and show that the method proposed is effective.
To distinguish chatter gestation, a new method of chatter prediction based on hybrid SOM/DHMM is proposed for dynamic patterns of chatter gestation in cutting process. At first FFT features are extracted from the vibr...
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ISBN:
(纸本)9783540742012
To distinguish chatter gestation, a new method of chatter prediction based on hybrid SOM/DHMM is proposed for dynamic patterns of chatter gestation in cutting process. At first FFT features are extracted from the vibration signal of cutting process, then FFT vectors are presorted and coded into code book of integer numbers by S OM (Self-Organizing Feature Map), and these code books are introduced to DHMM (Discrete Hidden Markov Models), for machine learning and classification. Finally the results of chatter gestation recognition and chatter prediction experiments are presented and show that the method proposed is effective.
Extracellular recording of the activity of 54 neurons in the rabbit visual cortex in responses to substitutions of eight colored and eight monochromatic stimuli in pairs was studied. Stimuli were uniform flashes of li...
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Two experiments investigated the effects of providing nonveridical knowledge of the results (KR) in a visuomanual task in which participants pointed to briefly (200 ms) presented targets without seeing their hand. By ...
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Two experiments investigated the effects of providing nonveridical knowledge of the results (KR) in a visuomanual task in which participants pointed to briefly (200 ms) presented targets without seeing their hand. By showing after each trial the movement endpoint displaced radially with respect to its true position, we were able to alter progressively the gain of the visuomanual loop. In experiment 1, the KR was provided only for transversal movements and for one target distance, but the effect generalized to all directions and all distances. Moreover, it also generalized to the other hand that had never been biased. In experiment 2, nonveridical KR was supplied for movements along the two major diagonals which require sharply different muscle synergies. The transfer to other directions and to the other hand was equally substantial. It is argued that the results support the vector coding hypothesis, which holds that the input to the motor execution stage is supplied by specifying independently the amplitude and the direction of the vector from the initial to the final position in an extrinsic frame of reference. We also discuss the possible brain structures involved in the biasing action of the KR.
Lentiviral vectors infect quiescent cells and allow for the delivery of genes to discrete brain regions. The present study assessed whether stable lentiviral gene transduction can be achieved in the monkey nigrostriat...
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Lentiviral vectors infect quiescent cells and allow for the delivery of genes to discrete brain regions. The present study assessed whether stable lentiviral gene transduction can be achieved in the monkey nigrostriatal system. Three young adult Rhesus monkeys received injections of a lentiviral vector encoding for the marker gene beta galatosidase (beta Gal). On one side of the brain, each monkey received multiple lentivirus injections into the caudate and putamen. On the opposite side, each animal received a single injection aimed at the substantia nigra. The first two monkeys were sacrificed 1 month postinjection, while the third monkey was sacrificed 3 months postinjection. Robust incorporation of the beta Gal gene was seen in the striatum of all three monkeys. Stereological counts revealed that 930,218;1,192,359;and 1,501,217 cells in the striatum were beta Gal positive in monkeys 1 (n = 2) and 3 (n = 1) months later, respectively. Only the third monkey had an injection placed directly into the substantia nigra and 187,308 beta Gal-positive cells were identified in this animal. The injections induced only mirror perivascular cuffing and there was no apparent inflammatory response resulting from the lentivirus injections. Double label experiments revealed that between 80 and 87% of the beta Gal-positive cells were neurons. These data indicate that robust transduction of striatal and nigral cells can occur in the nonhuman primate brain for up to 3 months. Studies are now ongoing testing the ability of lentivirus encoding for dopaminergic trophic factors to augment the nigrostriatal system in nonhuman primate models of Parkinson's disease. (C) 1999 Academic Press.
A linear technique for combining equalization and coset codes on partial response channels with additive white Gaussian noise is developed. The technique, vector coding, uses a set of transmit filters or 'vectors&...
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A linear technique for combining equalization and coset codes on partial response channels with additive white Gaussian noise is developed. The technique, vector coding, uses a set of transmit filters or 'vectors' to partition the channel into an independent set of parallel intersymbol interference (ISI)-free channels for any given finite (or infinite) block length. The optimal transmit vectors for such channel partitioning are shown to be the eigenvectors of the channel covariance matrix for the specified block length, and the gains of the individual channels are the eigenvalues. An optimal bit allocation and energy distribution, are derived for the set of parallel channels, under an accurate extension of the continuous approximation for power in optimal multidimensional signal sets for constellations with unequal signal spacing in different dimensions. Examples are presented that demonstrate performance advantages with respect to zero-forcing decision feedback methods that use the same coset code on the same partial response channel. Only resampling the channel at an optimal rate and assuming no errors in the feedback path will bring the performance of the decision feedback methods up to the level of the vector coded system.
The CPU time required to complete a cycle of restrained least-squares refinement of a protein structure from X-ray crystallographic data using the FORTRAN codes PROTIN and PROLSQ are reported for 48 different processo...
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The CPU time required to complete a cycle of restrained least-squares refinement of a protein structure from X-ray crystallographic data using the FORTRAN codes PROTIN and PROLSQ are reported for 48 different processors, ranging from single-user workstations to supercomputers. Sequential, vector, VLIW, multiprocessor, and RISC hardware architectures are compared using both a small and a large protein structure. Representative compile times for each hardware type are also given, and the improvement in run-time when coding for a specific hardware architecture considered. The benchmarks involve scalar integer and vector floating point arithmetic and are representative of the calculations performed in many scientific disciplines.
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