Reactions and Functional Relationships between Nonrespiratory Neurons in the Medulla Oblongata after Central Application of Penicillin

Changes in impulse activity of nonrespiratory neurons in the medulla oblongata produced by central administration of penicillin were studied in acute experiments on narcotized immobilized rats. The mean firing frequency increased in most neurons. The peaks on histograms for the distribution of interspike intervals were shifted toward shorter intervals and their amplitude increased; the type of distribution was also changed. Tonic activity of neurons was transformed into burst activity. Study of auto- and cross-correlation histograms for neuronal pairs showed that hyperactivation of structures was accompanied by an increase in the degree of synchronization. These changes reflect the appearance of new functional relationships between neurons in the respiratory center. We found that nonrespiratory reticular neurons are involved in the mechanisms of normal and pathological respiratory rhythm generation and serve as a functionally labile component of the neuronal respiratory network.     

Computation of Color and Brightness Differences by Rabbit Visual Cortex Neurons

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 light displayed on an SVGA monitor and illuminated the whole retina. The responses of phasic neurons showed an initial discharge (50–90 msec from the moment of the change in stimulus), associated with the brightness or color difference between the stimuli. These “discrimination discharges” were used to construct an 8 × 8 matrix for each neuron, showing the mean number of spikes per sec in responses to changes in different pairs of stimuli. Processing of the matrix by factor analysis identified the major factors determining the axes of the sensory space. A brightness space with only two dimensions, with darkness and brightness orthogonal axes, was seen for 30% of neurons. A four-dimensional color space was seen in 22% of neurons, with two color and two achromatic axes. The sensory space of these neurons was similar to the spaces obtained by analyzing the early components of visual evoked potentials in rabbits induced by changes in color stimuli and behavioral operant responses in conditioned reflex color differentiation. The fundamental coincidence of the sensory spaces obtained by different methods identifies the general nature of the principle of vector coding and the existence of special neuronal mechanisms for detection of color and brightness differences in the visual field. __________ Translated from Zhurnal Vysshei Nervnoi Deyatel'nosti imeni I. P. Pavlova, Vol. 55, No. 1, pp 60–70, January–February, 2005.     

家兔皮质脊髓束投射神经元的分布

将辣根过氧化物酶（ＨＲＰ）分别注入家兔脊髓单侧颈、胸、腰等不同节段，以显示皮质脊髓束投射神经元的分布。结果表明，大脑皮质的ＨＲＰ标记神经元仅见于颈段注入例，而胸段和腰段注入例未见到皮质标记神经元。标记的皮质脊髓束投射神经元主要分布于注入侧对侧的额叶无颗粒型皮质和顶叶颗粒型皮质，并呈现为３个分隔的标记细胞密集区，分别位于额叶皮质吻侧端的内侧部、邻近前囟的额顶叶皮质、顶叶皮质的外侧部。标记神经元呈柱状     

The irre Cell Recognition Module (IRM) Protein Kirre Is Required to Form the Reciprocal Synaptic Network of L4 Neurons in the Drosophila Lamina

Each neuropil module, or cartridge, in the fly's lamina has a fixed complement of cells. Of five types of monopolar cell interneurons, only L4 has collaterals that invade neighboring cartridges. In the proximal lamina, these collaterals form reciprocal synapses with both the L2 of their own cartridge and the L4 collateral branches from two other neighboring cartridges. During synaptogenesis, L4 collaterals strongly express the cell adhesion protein Kirre, a member of the irre cell recognition module (IRM) group of proteins (, J Neurogenet, 23, 48–67). The authors show by mutant analysis and gene knockdown techniques that L4 neurons develop their lamina collaterals in the absence of this cell adhesion protein. Using electron microscopy (EM), the authors demonstrate, however, that without Kirre protein these L4 collaterals selectively form fewer synapses. The collaterals of L4 neurons of various genotypes reconstructed from serial-section EM revealed that the number of postsynaptic sites was dramatically reduced in the absence of Kirre, almost eliminating any synaptic input to L4 neurons. A significant reduction of presynaptic sites was also detected in kirre⁰ mutants and gene knockdown flies using RNA interference. L4 neuron reciprocal synapses are thus almost eliminated. A presynaptic marker, Brp-short^GFP confirmed these data using confocal microscopy. This study reveals that removing Kirre protein specifically disrupts the functional L4 synaptic network in the Drosophila lamina.